Support OverloadedRecordDot (#310)

* Support OverloadedRecordDot

* stylish

* Haddocks

* Add comments to README

.editorconfig

@@ -11,8 +11,8 @@ insert_final_newline = true
 
 [*.{hs,md,php}]
 indent_style = space
-indent_size = 2
-tab_width = 2
+indent_size = 4
+tab_width = 4
 end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,13 +1,14 @@
 Before submitting your PR, check that you've:
 
-- [ ] Bumped the version number
-- [ ] Documented new APIs with [Haddock markup](https://www.haskell.org/haddock/doc/html/index.html)
-- [ ] Added [`@since` declarations](http://haskell-haddock.readthedocs.io/en/latest/markup.html#since) to the Haddock
+- [ ] Bumped the version number.
+- [ ] Documented new APIs with [Haddock markup](https://www.haskell.org/haddock/doc/html/index.html).
+- [ ] Added [`@since` declarations](http://haskell-haddock.readthedocs.io/en/latest/markup.html#since) to the Haddock.
+- [ ] Ran `stylish-haskell` and otherwise adhered to the [style guide](https://github.com/bitemyapp/esqueleto/blob/master/style-guide.yaml).
 
 After submitting your PR:
 
-- [ ] Update the Changelog.md file with a link to your PR
-- [ ] Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts)
+- [ ] Update the Changelog.md file with a link to your PR.
+- [ ] Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts).
 
 <!---Thanks so much for contributing! :)
 

.github/workflows/haskell.yml

@@ -0,0 +1,76 @@
+name: CI
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types:
+      - opened
+      - synchronize
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    services:
+      # mysql-service Label used to access the service container
+      mysql-service:
+        # Docker Hub image (also with version)
+        image: mysql:8.0
+        env:
+          ## Accessing to Github secrets, where you can store your configuration
+          MYSQL_USER: travis
+          MYSQL_PASSWORD: esqutest
+          MYSQL_ROOT_PASSWORD: esqutest
+          MYSQL_DATABASE: esqutest
+        ## map the "external" 33306 port with the "internal" 3306
+        ports:
+          - 33306:3306
+        # Set health checks to wait until mysql database has started (it takes some seconds to start)
+        options: >-
+          --health-cmd="mysqladmin ping"
+          --health-interval=10s
+          --health-timeout=5s
+          --health-retries=3
+    strategy:
+      matrix:
+        cabal: ["3.6"]
+        ghc: ["8.6.5", "8.8.4", "8.10.4", "9.0.2", "9.2.2"]
+    env:
+      CONFIG: "--enable-tests --enable-benchmarks "
+    steps:
+      - uses: actions/checkout@v2
+      - uses: haskell/actions/setup@v1
+        id: setup-haskell-cabal
+        with:
+          ghc-version: ${{ matrix.ghc }}
+          cabal-version: ${{ matrix.cabal }}
+      - uses: harmon758/postgresql-action@v1
+        with:
+           postgresql version: '12'  # See https://hub.docker.com/_/postgres for available versions  
+           postgresql user: esqutest
+           postgresql password: esqutest
+           postgresql db: esqutest
+      - name: Create MySQL
+        run: mysql -utravis -pesqutest -h127.0.0.1 --port=33306 esqutest -e "SELECT 1;"
+            # - name: Shutdown Ubuntu MySQL (SUDO)
+            #   run: sudo service mysql stop
+            # - uses: mirromutth/mysql-action@v1.1
+            #   with:
+            #     mysql version: '8.0' # Optional, default value is "latest". The version of the MySQL
+            #     mysql database: 'esqutest' # Optional, default value is "test". The specified database which will be create
+            #     mysql user: 'travis' # Required if "mysql root password" is empty, default is empty. The superuser for the specified database. Can use secrets, too
+            #     mysql password: 'esqutest' # Required if "mysql user" exists. The password for the "mysql user"
+      - run: cabal v2-update
+      - run: cabal v2-freeze $CONFIG
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ${{ steps.setup-haskell-cabal.outputs.cabal-store }}
+            dist-newstyle
+          key: ${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('cabal.project.freeze') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('cabal.project.freeze') }}
+            ${{ runner.os }}-${{ matrix.ghc }}-
+      - run: cabal v2-build --disable-optimization -j $CONFIG
+      - run: cabal v2-test --disable-optimization -j $CONFIG --test-options "--fail-on-focus"
+      - run: cabal v2-haddock -j $CONFIG
+      - run: cabal v2-sdist

.gitignore

@@ -1,7 +1,10 @@
 .stack-work
 stack.yaml.lock
+*.yaml.lock
 /dist*
 *~
 .cabal-sandbox/
 cabal.sandbox.config
 .hspec-failures
+*.sqlite*
+cabal.project.freeze

.stylish-haskell.yaml

@@ -0,0 +1,39 @@
+steps:
+  - imports:
+      align: none
+      list_align: with_module_name
+      pad_module_names: false
+      long_list_align: new_line_multiline
+      empty_list_align: inherit
+      list_padding: 7 # length "import "
+      separate_lists: false
+      space_surround: false
+  - language_pragmas:
+      style: vertical
+      align: false
+      remove_redundant: true
+  - simple_align:
+      cases: false
+      top_level_patterns: false
+      records: false
+  - trailing_whitespace: {}
+indent: 4
+columns: 80
+newline: native
+language_extensions:
+  - BlockArguments
+  - DataKinds
+  - DeriveGeneric
+  - DerivingStrategies
+  - DerivingVia
+  - ExplicitForAll
+  - FlexibleContexts
+  - MultiParamTypeClasses
+  - NamedFieldPuns
+  - OverloadedStrings
+  - QuantifiedConstraints
+  - RecordWildCards
+  - ScopedTypeVariables
+  - TemplateHaskell
+  - TypeApplications
+  - ViewPatterns

.travis.yml

@@ -1,7 +1,5 @@
 language: c
 
-sudo: false
-
 services:
   - mysql
 
@@ -25,8 +23,9 @@ env:
     - GHCVER=nightly
 
 jobs:
+  fast_finish: true
   allow_failures:
-    - GHCVER=nightly
+    - env: GHCVER=nightly
 
 install:
   - export STACK_YAML=stack-$GHCVER.yaml

Makefile

@@ -21,7 +21,19 @@ test-ghci:
 	stack ghci esqueleto:test:sqlite
 
 test-ghcid:
-	ghcid -c "stack ghci --ghci-options -fobject-code esqueleto:test:sqlite"
+	ghcid -c "stack ghci --ghci-options -fobject-code esqueleto --test" \
+		--warnings \
+		--restart "stack.yaml" \
+		--restart "esqueleto.cabal" \
+		--test main
+
+test-ghcid-build:
+	ghcid -c "stack ghci --ghci-options -fobject-code esqueleto --test" \
+		--warnings \
+		--restart "stack.yaml" \
+		--restart "esqueleto.cabal"
+
+
 
 init-pgsql:
 	sudo -u postgres -- createuser -s esqutest

README.md

@@ -1,4 +1,4 @@
-Esqueleto [![TravisCI](https://travis-ci.org/bitemyapp/esqueleto.svg)](https://travis-ci.org/bitemyapp/esqueleto)
+Esqueleto [![CI](https://github.com/bitemyapp/esqueleto/actions/workflows/haskell.yml/badge.svg?branch=master)](https://github.com/bitemyapp/esqueleto/actions/workflows/haskell.yml)
 ==========
 
 ![Skeleton](./esqueleto.png)
@@ -127,7 +127,61 @@ FROM Person
 WHERE Person.age >= 18
 ```
 
-Since `age` is an optional `Person` field, we use `just` to lift`val 18 :: SqlExpr (Value Int)` into `just (val 18) ::SqlExpr (Value (Maybe Int))`.
+Since `age` is an optional `Person` field, we use `just` to lift `val 18 :: SqlExpr (Value Int)` into `just (val 18) ::SqlExpr (Value (Maybe Int))`.
+
+### Alternative Field Projections
+
+The `(^.)` operator works on an `EntityField` value, which are generated by
+`persistent` as the table name + the field name. This can get a little bit
+verbose. As of `persistent-2.11`, you can use `OverloadedLabels` to make this a
+bit more concise:
+
+```haskell
+{-# LANGUAGE OverloadedLabels #-}
+
+select $ do
+    p <- from $ table @Person
+    pure
+        ( p ^. PersonName
+        , p ^. #name
+        )
+```
+
+The `OverloadedLabels` support uses the `fieldName` as given by the Persistent
+entity definition syntax - no type name prefix necessary. Additionally, these
+field accesses are *polymorphic* - the following query filters any table that
+has a `name` column:
+
+```haskell
+rowsByName
+    :: forall rec.
+    ( PersistEntity rec
+    , PersistEntityBackend rec ~ SqlBackend
+    , SymbolToField "name" rec Text
+    )
+    => SqlExpr (Value Text)
+    -> SqlQuery (SqlExpr (Entity rec))
+rowsByName name = do
+    rec <- from $ table @rec
+    where_ $ rec ^. #name ==. name
+    pure rec
+```
+
+GHC 9.2 introduces the `OverloadedRecordDot` language extension, and `esqueleto`
+supports this on `SqlExpr (Entity rec)` and `SqlExpr (Maybe (Entity rec))`. It
+looks like this:
+
+```haskell
+select $ do
+    (person, blogPost) <-
+        from $
+            table @Person
+            `leftJoin` table @BlogPost
+            `on` do
+                \(person :& blogPost) ->
+                    just person.id ==. blogPost.authorId
+    pure (person.name, blogPost.title)
+```
 
 ## Experimental/New Joins
 
@@ -487,5 +541,6 @@ user which can access it:
 ```
 mysql> CREATE DATABASE esqutest;
 mysql> CREATE USER 'travis'@'localhost';
-mysql> GRANT ALL ON esqutest.* TO 'travis';
+mysql> ALTER USER 'travis'@'localhost' IDENTIFIED BY 'esqutest';
+mysql> GRANT ALL ON esqutest.* TO 'travis'@'localhost';
 ```

cabal.project

@@ -0,0 +1,5 @@
+-- Generated by stackage-to-hackage
+
+packages:
+    ./
+  , examples/

changelog.md

@@ -1,9 +1,149 @@
-3.3.4.1
+3.5.4.0
+=======
+- @parsonsmatt
+    - [#310](https://github.com/bitemyapp/esqueleto/pull/310)
+        - Add instances of `HasField` for `SqlExpr (Entity rec)` and `SqlExpr
+          (Maybe (Entity rec))`. These instances allow you to use the
+          `OverloadedRecordDot` language extension in GHC 9.2 with SQL
+          representations of database entities.
 
+3.5.3.2
+=======
+- @parsonsmatt
+    - [#309](https://github.com/bitemyapp/esqueleto/pull/309)
+        - Bump `time` version bound
+
+3.5.3.1
+=======
+- @jappeace
+  - [#303](https://github.com/bitemyapp/esqueleto/pull/303)
+      - Added docs for delete function for new experimental API.
+
+3.5.3.0
+=======
+- @m4dc4p
+  - [#291](https://github.com/bitemyapp/esqueleto/pull/291)
+         - Added `ToAlias` and `ToAliasReference` instaces to the `:&` type, mirroring
+         the tuple instances for the same classes. See [Issue #290](https://github.com/bitemyapp/esqueleto/issues/290)
+         for discussion.
+- @NikitaRazmakhnin
+  - [#284](https://github.com/bitemyapp/esqueleto/pull/284)
+        - Add PostgreSQL-specific support of VALUES(..) literals
+
+
+3.5.2.2
+=======
+- @NikitaRazmakhnin
+  - [#278](https://github.com/bitemyapp/esqueleto/pull/278)
+        - Fix generating of bad sql using nexted expressions with `distinctOnOrderBy`.
+
+3.5.2.1
+=======
+- @cdparks
+  - [#273](https://github.com/bitemyapp/esqueleto/pull/273)
+        - Avoid generating an empty list as the left operand to `NOT IN`.
+
+3.5.2.0
+=======
+- @ivanbakel
+  - [#268](https://github.com/bitemyapp/esqueleto/pull/268)
+        - Added `SqlSelect` instance for `(:&)`, allowing it to be returned from
+          queries just like `(,)` tuples.
+
+3.5.1.0
+=======
+- @ibarrae
+  - [#265](https://github.com/bitemyapp/esqueleto/pull/265)
+        - Added `selectOne`
+
+3.5.0.0
+=======
+- @belevy
+  - [#228](https://github.com/bitemyapp/esqueleto/pull/228)
+        - Destroy all GADTs; Removes the From GADT and SqlExpr GADT
+        - From GADT is replaced with a From data type and FromRaw
+        - SqlExpr is now all defined in terms of ERaw
+        - Modified ERaw to contain a SqlExprMeta with any extra information
+          that may be needed
+        - Experimental top level is now strictly for documentation and all the
+          implementation details are in Experimental.* modules
+- @parsonsmatt
+    - [#259](https://github.com/bitemyapp/esqueleto/pull/259)
+        - Create the `Database.Esqueleto.Legacy` module. The
+          `Database.Esqueleto` module now emits a warning, directing users to
+          either import `Database.Esqueleto.Legacy` to keep the old behavior or
+          to import `Database.Esqueleto.Experimental` to opt in to the new
+          behavior.
+        - Deleted the deprecated modules
+          `Database.Esqueleto.Internal.{Language,Sql}`. Please use
+          `Database.Esqueleto.Internal.Internal` instead, or ideally post what
+          you need from the library so we can support you safely.
+        - Support GHC 9
+
+3.4.2.2
+=======
+- @parsonsmatt
+  - [#255](https://github.com/bitemyapp/esqueleto/pull/255)
+    - Fix a bug where a composite primary key in a `groupBy` clause would break.
+
+3.4.2.1
+=======
+- @parsonsmatt
+  - [#245](https://github.com/bitemyapp/esqueleto/pull/245)
+    - Support `persistent-2.13`
+
+3.4.2.0
+=======
+- @parsonsmatt
+  - [#243](https://github.com/bitemyapp/esqueleto/pull/243)
+    - Support `persistent-2.12`
+
+3.4.1.1
+=======
+- @MaxGabriel
+  - [#240](https://github.com/bitemyapp/esqueleto/pull/240/files)
+    - Improve recommend hlint to avoid doing `x = NULL` SQL queries
+
+3.4.1.0
+=======
+- @arthurxavierx
+  - [#238](https://github.com/bitemyapp/esqueleto/pull/238)
+    - Fix non-exhaustive patterns in `unsafeSqlAggregateFunction`
+- @Vlix
+  - [#232](https://github.com/bitemyapp/esqueleto/pull/232)
+    - Export the `ValidOnClauseValue` type family
+
+
+3.4.0.1
+=======
+- @arthurxavierx
+  - [#221](https://github.com/bitemyapp/esqueleto/pull/221)
+    - Deprecate `ToAliasT` and `ToAliasReferenceT`
+- @parsonsmatt
+  - [#226](https://github.com/bitemyapp/esqueleto/pull/226)
+    - Support `persistent-2.11`
+- @belevy
+  - [#225](https://github.com/bitemyapp/esqueleto/pull/225)
+    - Simplify `ToFromT` extracting the overlapping and type error instances
+    - Make `ToFromT` and associated type family of `ToFrom`
+
+3.4.0.0
+=======
+- @belevy, @charukiewicz
+  - [#215](https://github.com/bitemyapp/esqueleto/pull/215)
+    - Added support for common table expressions (`with`, `withRecursive`)
+    - Added support for lateral JOINs with updated example (Example #6)
+    - Deprecated `SelectQuery`, removing the neccessity to tag `SqlQuery` values
+    - Deprecated use of data constructors for SQL set operations (replaced with functions)
+    - Refactored module structure to fix haddock build (fixes build from `3.3.4.0`)
+
+3.3.4.1
+=======
 - @maxgabriel
   - [#214](https://github.com/bitemyapp/esqueleto/pull/214)
     - Add suggested hlint rules for proper `isNothing` usage
 
+
 3.3.4.0
 =======
 - @parsonsmatt

esqueleto.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           esqueleto
-version:        3.3.4.1
+version:        3.5.4.0
 synopsis:       Type-safe EDSL for SQL queries on persistent backends.
 description:    @esqueleto@ is a bare bones, type-safe EDSL for SQL queries that works with unmodified @persistent@ SQL backends.  Its language closely resembles SQL, so you don't have to learn new concepts, just new syntax, and it's fairly easy to predict the generated SQL and optimize it for your backend. Most kinds of errors committed when writing SQL are caught as compile-time errors---although it is possible to write type-checked @esqueleto@ queries that fail at runtime.
                 .
@@ -23,152 +23,106 @@ extra-source-files:
     changelog.md
 
 source-repository head
-  type: git
-  location: git://github.com/bitemyapp/esqueleto.git
+    type: git
+    location: git://github.com/bitemyapp/esqueleto.git
 
 library
-  exposed-modules:
-      Database.Esqueleto
-      Database.Esqueleto.Experimental
-      Database.Esqueleto.Internal.Language
-      Database.Esqueleto.Internal.Sql
-      Database.Esqueleto.Internal.Internal
-      Database.Esqueleto.Internal.ExprParser
-      Database.Esqueleto.MySQL
-      Database.Esqueleto.PostgreSQL
-      Database.Esqueleto.PostgreSQL.JSON
-      Database.Esqueleto.SQLite
-  other-modules:
-      Database.Esqueleto.Internal.PersistentImport
-      Database.Esqueleto.PostgreSQL.JSON.Instances
-      Paths_esqueleto
-  hs-source-dirs:
-      src/
-  build-depends:
-      base >=4.8 && <5.0
-    , aeson >=1.0
-    , attoparsec >= 0.13 && < 0.14
-    , blaze-html
-    , bytestring
-    , conduit >=1.3
-    , containers
-    , monad-logger
-    , persistent >=2.10.0 && <2.11
-    , resourcet >=1.2
-    , tagged >=0.2
-    , text >=0.11 && <1.3
-    , time >=1.5.0.1 && <=1.10
-    , transformers >=0.2
-    , unliftio
-    , unordered-containers >=0.2
-  if impl(ghc >=8.0)
-    ghc-options: -Wall -Wno-redundant-constraints
-  else
-    ghc-options: -Wall
-  default-language: Haskell2010
+    exposed-modules:
+        Database.Esqueleto
+        Database.Esqueleto.Legacy
+        Database.Esqueleto.Experimental
+        Database.Esqueleto.Internal.Internal
+        Database.Esqueleto.Internal.ExprParser
+        Database.Esqueleto.MySQL
+        Database.Esqueleto.PostgreSQL
+        Database.Esqueleto.PostgreSQL.JSON
+        Database.Esqueleto.SQLite
+        Database.Esqueleto.Experimental.From
+        Database.Esqueleto.Experimental.From.CommonTableExpression
+        Database.Esqueleto.Experimental.From.Join
+        Database.Esqueleto.Experimental.From.SqlSetOperation
+        Database.Esqueleto.Experimental.ToAlias
+        Database.Esqueleto.Experimental.ToAliasReference
+        Database.Esqueleto.Experimental.ToMaybe
+    other-modules:
+        Database.Esqueleto.PostgreSQL.JSON.Instances
+        Database.Esqueleto.Internal.PersistentImport
+        Paths_esqueleto
+    hs-source-dirs:
+        src/
+    build-depends:
+        base >=4.8 && <5.0
+      , aeson >=1.0
+      , attoparsec >= 0.13 && < 0.15
+      , blaze-html
+      , bytestring
+      , conduit >=1.3
+      , containers
+      , monad-logger
+      , persistent >=2.13 && <3
+      , resourcet >=1.2
+      , tagged >=0.2
+      , text >=0.11 && <1.3
+      , time >=1.5.0.1 && <=1.13
+      , transformers >=0.2
+      , unliftio
+      , unordered-containers >=0.2
+    ghc-options:
+        -Wall
+        -Wno-redundant-constraints
+        -Wincomplete-uni-patterns
+        -Wincomplete-record-updates
+        -Wpartial-fields
+        -Wmissing-home-modules
+        -Widentities
+        -Wcpp-undef
+        -Wcpp-undef
+    default-language: Haskell2010
 
-test-suite mysql
-  type: exitcode-stdio-1.0
-  main-is: MySQL/Test.hs
-  other-modules:
-      Common.Test
-      Paths_esqueleto
-  hs-source-dirs:
-      test
-  ghc-options: -Wall
-  build-depends:
-      base >=4.8 && <5.0
-    , attoparsec
-    , blaze-html
-    , bytestring
-    , conduit >=1.3
-    , containers
-    , esqueleto
-    , exceptions
-    , hspec
-    , monad-logger
-    , mtl
-    , mysql
-    , mysql-simple
-    , persistent >=2.8.0 && <2.11
-    , persistent-mysql
-    , persistent-template
-    , resourcet >=1.2
-    , tagged >=0.2
-    , text >=0.11 && <1.3
-    , time 
-    , transformers >=0.2
-    , unliftio
-    , unordered-containers >=0.2
-  default-language: Haskell2010
-
-test-suite postgresql
-  type: exitcode-stdio-1.0
-  main-is: PostgreSQL/Test.hs
-  other-modules:
-      Common.Test
-      PostgreSQL.MigrateJSON
-      Paths_esqueleto
-  hs-source-dirs:
-      test
-  ghc-options: -Wall
-  build-depends:
-      base >=4.8 && <5.0
-    , aeson
-    , attoparsec
-    , blaze-html
-    , bytestring
-    , conduit >=1.3
-    , containers
-    , esqueleto
-    , exceptions
-    , hspec
-    , monad-logger
-    , mtl
-    , persistent >=2.10.0 && <2.11
-    , persistent-postgresql >= 2.10.0 && <2.11
-    , persistent-template
-    , postgresql-libpq
-    , postgresql-simple
-    , resourcet >=1.2
-    , tagged >=0.2
-    , text >=0.11 && <1.3
-    , time 
-    , transformers >=0.2
-    , unliftio
-    , unordered-containers >=0.2
-    , vector
-  default-language: Haskell2010
-
-test-suite sqlite
-  type: exitcode-stdio-1.0
-  main-is: SQLite/Test.hs
-  other-modules:
-      Common.Test
-      Paths_esqueleto
-  hs-source-dirs:
-      test
-  ghc-options: -Wall
-  build-depends:
-      base >=4.8 && <5.0
-    , attoparsec
-    , blaze-html
-    , bytestring
-    , conduit >=1.3
-    , containers
-    , esqueleto
-    , exceptions
-    , hspec
-    , monad-logger
-    , mtl
-    , persistent >=2.8.0 && <2.11
-    , persistent-sqlite
-    , persistent-template
-    , resourcet >=1.2
-    , tagged >=0.2
-    , text >=0.11 && <1.3
-    , time 
-    , transformers >=0.2
-    , unliftio
-    , unordered-containers >=0.2
-  default-language: Haskell2010
+test-suite specs
+    type: exitcode-stdio-1.0
+    main-is: Spec.hs
+    other-modules:
+        Common.Test
+        Common.Test.Models
+        Common.Test.Import
+        Common.Test.Select
+        PostgreSQL.MigrateJSON
+        SQLite.Test
+        PostgreSQL.Test
+        MySQL.Test
+    default-extensions:
+        RankNTypes
+    hs-source-dirs:
+        test
+    ghc-options: -Wall -threaded
+    build-depends:
+        base >=4.8 && <5.0
+      , aeson
+      , attoparsec
+      , blaze-html
+      , bytestring
+      , conduit
+      , containers
+      , esqueleto
+      , exceptions
+      , hspec
+      , hspec-core
+      , monad-logger
+      , mtl
+      , mysql
+      , mysql-simple
+      , persistent
+      , persistent-mysql
+      , persistent-postgresql
+      , persistent-sqlite
+      , postgresql-simple
+      , QuickCheck
+      , resourcet
+      , tagged
+      , text
+      , time
+      , transformers
+      , unliftio
+      , unordered-containers
+    default-language: Haskell2010

examples/.gitignore

@@ -1 +0,0 @@
-*.cabal

examples/Blog.hs

@@ -11,7 +11,7 @@ module Blog
 
 import           Control.Monad.Base          (MonadBase (..))
 import           Control.Monad.IO.Unlift     (MonadUnliftIO(..), wrappedWithRunInIO)
-import           Control.Monad.Logger        (MonadLogger, NoLoggingT (..))
+import           Control.Monad.Logger        (MonadLoggerIO, MonadLogger, NoLoggingT (..))
 import           Control.Monad.Reader
 import           Control.Monad.Trans.Control (ComposeSt, MonadBaseControl (..),
                                               MonadTransControl (..),
@@ -26,6 +26,7 @@ newtype BlogT m a = BlogT { unBlogT :: NoLoggingT (ReaderT ConnectionString m) a
            , MonadLogger
            , MonadReader ConnectionString
            , MonadIO
+           , MonadLoggerIO
            )
 
 instance MonadUnliftIO m => MonadUnliftIO (BlogT m) where

examples/Main.hs

@@ -1,42 +1,44 @@
-{-# LANGUAGE DerivingStrategies, FlexibleContexts           #-}
-{-# LANGUAGE FlexibleInstances          #-}
-{-# LANGUAGE GADTs                      #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE MultiParamTypeClasses      #-}
-{-# LANGUAGE OverloadedStrings          #-}
-{-# LANGUAGE QuasiQuotes                #-}
-{-# LANGUAGE ScopedTypeVariables        #-}
-{-# LANGUAGE StandaloneDeriving         #-}
-{-# LANGUAGE TemplateHaskell            #-}
-{-# LANGUAGE TypeFamilies               #-}
-{-# LANGUAGE UndecidableInstances       #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -fno-warn-unused-top-binds #-}
 
 module Main
     ( main
     ) where
 
-import           Blog
-import           Control.Monad               (void)
-import           Control.Monad               (forM_)
-import           Control.Monad.IO.Class      (MonadIO, liftIO)
-import           Control.Monad.IO.Unlift     (MonadUnliftIO)
-import           Control.Monad.Logger        (MonadLogger)
-import           Control.Monad.Reader        (MonadReader (..), runReaderT)
-import           Control.Monad.Trans.Control (MonadBaseControl)
-import           Data.Monoid                 ((<>))
-import           Database.Esqueleto
-import           Database.Persist.Postgresql (ConnectionString,
-                                              withPostgresqlConn)
-import           Database.Persist.TH         ( AtLeastOneUniqueKey(..)
-                                             , OnlyOneUniqueKey(..)
-                                             , mkDeleteCascade
-                                             , mkMigrate
-                                             , mkPersist
-                                             , persistLowerCase
-                                             , share
-                                             , sqlSettings
-                                             )
+import Blog
+import Control.Monad (void)
+import Control.Monad (forM_)
+import Control.Monad.IO.Class (MonadIO, liftIO)
+import Control.Monad.IO.Unlift (MonadUnliftIO)
+import Control.Monad.Logger (MonadLogger, MonadLoggerIO)
+import Control.Monad.Reader (MonadReader(..), runReaderT)
+import Control.Monad.Trans.Control (MonadBaseControl)
+import Data.Monoid ((<>))
+import Database.Esqueleto
+import Database.Persist.Postgresql (ConnectionString, withPostgresqlConn)
+import Database.Persist.TH
+       ( AtLeastOneUniqueKey(..)
+       , OnlyOneUniqueKey(..)
+       , mkDeleteCascade
+       , mkMigrate
+       , mkPersist
+       , persistLowerCase
+       , share
+       , sqlSettings
+       )
 
 
 share [ mkPersist sqlSettings
@@ -163,6 +165,7 @@ runDB :: (MonadReader ConnectionString m,
           MonadIO m,
           MonadBaseControl IO m,
           MonadUnliftIO m,
+          MonadLoggerIO m,
           MonadLogger m)
       => SqlPersistT m a -> m a
 runDB query = do

examples/esqueleto-examples.cabal

@@ -0,0 +1,49 @@
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.34.4.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: d5fddaf37d0c2f27fb2446f5038899d766102efd74ccfe4c7bcd02c61837e6b6
+
+name:           esqueleto-examples
+version:        0.0.0.0
+category:       Database
+homepage:       https://github.com/bitemyapp/esqueleto#readme
+bug-reports:    https://github.com/bitemyapp/esqueleto/issues
+author:         Fintan Halpenny
+maintainer:     cma@bitemyapp.com
+copyright:      2019, Chris Allen
+license:        BSD3
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+
+source-repository head
+  type: git
+  location: https://github.com/bitemyapp/esqueleto
+
+flag werror
+  description: Treat warnings as errors
+  manual: True
+  default: False
+
+executable blog-example
+  main-is: Main.hs
+  other-modules:
+      Blog
+  ghc-options: -Wall -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base
+    , esqueleto
+    , monad-control
+    , monad-logger
+    , mtl
+    , persistent >=2.12
+    , persistent-postgresql
+    , transformers-base
+    , unliftio-core
+  if flag(werror)
+    ghc-options: -Werror
+  default-language: Haskell2010

examples/package.yaml

@@ -13,8 +13,7 @@ extra-source-files:
 dependencies:
 - base
 - esqueleto
-- persistent
-- persistent-template
+- persistent >= 2.12
 - persistent-postgresql
 - mtl
 - monad-logger

src/Database/Esqueleto.hs

@@ -1,4 +1,8 @@
-{-# LANGUAGE FlexibleContexts, FlexibleInstances, GADTs, RankNTypes #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE RankNTypes #-}
+
 -- | The @esqueleto@ EDSL (embedded domain specific language).
 -- This module replaces @Database.Persist@, so instead of
 -- importing that module you should just import this one:
@@ -28,11 +32,15 @@
 -- Other than identifier name clashes, @esqueleto@ does not
 -- conflict with @persistent@ in any way.
 --
--- Note that the faciliites for @JOIN@ have been significantly improved in the
+-- Note that the facilities for @JOIN@ have been significantly improved in the
 -- "Database.Esqueleto.Experimental" module. The definition of 'from' and 'on'
 -- in this module will be replaced with those at the 4.0.0.0 version, so you are
 -- encouraged to migrate to the new method.
-module Database.Esqueleto
+--
+-- This module has an attached WARNING message indicating that the Experimental
+-- syntax will become the default. If you want to continue using the old syntax,
+-- please refer to "Database.Esqueleto.Legacy" as a drop-in replacement.
+module Database.Esqueleto {-# WARNING "This module will switch over to the Experimental syntax in an upcoming major version release. Please migrate to the Database.Esqueleto.Legacy module to continue using the old syntax, or translate to the new and improved syntax in Database.Esqueleto.Experimental." #-}
   ( -- * Setup
     -- $setup
 
@@ -89,6 +97,7 @@ module Database.Esqueleto
   , SqlExpr
   , SqlEntity
   , select
+  , selectOne
   , selectSource
   , delete
   , deleteCount
@@ -120,14 +129,8 @@ module Database.Esqueleto
   , module Database.Esqueleto.Internal.PersistentImport
   ) where
 
-import Control.Monad.IO.Class (MonadIO)
-import Control.Monad.Trans.Reader (ReaderT)
-import Data.Int (Int64)
-import qualified Data.Map.Strict as Map
-import Database.Esqueleto.Internal.Language
-import Database.Esqueleto.Internal.Sql
+import Database.Esqueleto.Legacy
 import Database.Esqueleto.Internal.PersistentImport
-import qualified Database.Persist
 
 
 -- $setup
@@ -410,66 +413,3 @@ import qualified Database.Persist
 --
 -- In order to use these functions, you need to explicitly import
 -- their corresponding modules, they're not re-exported here.
-
-
-----------------------------------------------------------------------
-
-
--- | @valkey i = 'val' . 'toSqlKey'@
--- (<https://github.com/prowdsponsor/esqueleto/issues/9>).
-valkey :: (ToBackendKey SqlBackend entity, PersistField (Key entity)) =>
-          Int64 -> SqlExpr (Value (Key entity))
-valkey = val . toSqlKey
-
-
--- | @valJ@ is like @val@ but for something that is already a @Value@. The use
--- case it was written for was, given a @Value@ lift the @Key@ for that @Value@
--- into the query expression in a type safe way. However, the implementation is
--- more generic than that so we call it @valJ@.
---
--- Its important to note that the input entity and the output entity are
--- constrained to be the same by the type signature on the function
--- (<https://github.com/prowdsponsor/esqueleto/pull/69>).
---
--- /Since: 1.4.2/
-valJ :: (PersistField (Key entity)) =>
-        Value (Key entity) -> SqlExpr (Value (Key entity))
-valJ = val . unValue
-
-
-----------------------------------------------------------------------
-
-
--- | Synonym for 'Database.Persist.Store.delete' that does not
--- clash with @esqueleto@'s 'delete'.
-deleteKey :: ( PersistStore backend
-             , BaseBackend backend ~ PersistEntityBackend val
-             , MonadIO m
-             , PersistEntity val )
-          => Key val -> ReaderT backend m ()
-deleteKey = Database.Persist.delete
-
--- | Avoid N+1 queries and join entities into a map structure
--- @
--- getFoosAndNestedBarsFromParent :: ParentId -> (Map (Key Foo) (Foo, [Maybe (Entity Bar)]))
--- getFoosAndNestedBarsFromParent parentId = 'fmap' associateJoin $ 'select' $
--- 'from' $ \\(foo `'LeftOuterJoin`` bar) -> do
---   'on' (bar '?.' BarFooId '==.' foo '^.' FooId)
---   'where_' (foo '^.' FooParentId '==.' 'val' parentId)
---   'pure' (foo, bar)
--- @
---
--- @since 3.1.2
-associateJoin
-  :: forall e1 e0
-   . Ord (Key e0)
-  => [(Entity e0, e1)]
-  -> Map.Map (Key e0) (e0, [e1])
-associateJoin = foldr f start
-  where
-    start = Map.empty
-    f (one, many) =
-      Map.insertWith
-        (\(oneOld, manyOld) (_, manyNew) -> (oneOld, manyNew ++ manyOld ))
-        (entityKey one)
-        (entityVal one, [many])

src/Database/Esqueleto/Experimental.hs

@@ -1,23 +1,11 @@
-{-# LANGUAGE CPP
-           , DataKinds
-           , FlexibleContexts
-           , FlexibleInstances
-           , FunctionalDependencies
-           , GADTs
-           , MultiParamTypeClasses
-           , TypeOperators
-           , TypeFamilies
-           , UndecidableInstances
-           , OverloadedStrings
-           , PatternSynonyms
- #-}
+{-# LANGUAGE PatternSynonyms #-}
 
 -- | This module contains a new way (introduced in 3.3.3.0) of using @FROM@ in
 -- Haskell. The old method was a bit finicky and could permit runtime errors,
 -- and this new way is both significantly safer and much more powerful.
 --
--- Esqueleto users are encouraged to migrate to this module, as it will become
--- the default in a new major version @4.0.0.0@.
+-- This syntax will become the default syntax exported from the library in
+-- version @3.6.0.0@. To use the old syntax, see "Database.Esqueleto.Legacy".
 module Database.Esqueleto.Experimental
     ( -- * Setup
       -- $setup
@@ -30,59 +18,217 @@ module Database.Esqueleto.Experimental
 
       -- * Documentation
 
-      SqlSetOperation(Union, UnionAll, Except, Intersect)
-    , pattern SelectQuery
-    , From(..)
-    , on
-    , from
+    -- ** Basic Queries
+      from
+    , table
+    , Table(..)
+    , SubQuery(..)
+    , selectQuery
+
+    -- ** Joins
     , (:&)(..)
-      -- * Internals
-    , ToFrom(..)
-    , ToFromT
+    , on
+    , innerJoin
+    , innerJoinLateral
+    , leftJoin
+    , leftJoinLateral
+    , rightJoin
+    , fullOuterJoin
+    , crossJoin
+    , crossJoinLateral
+
+      -- ** Set Operations
+      -- $sql-set-operations
+    , union_
+    , Union(..)
+    , unionAll_
+    , UnionAll(..)
+    , except_
+    , Except(..)
+    , intersect_
+    , Intersect(..)
+    , pattern SelectQuery
+
+      -- ** Common Table Expressions
+    , with
+    , withRecursive
+
+      -- ** Internals
+    , From(..)
     , ToMaybe(..)
-    , ToMaybeT
     , ToAlias(..)
     , ToAliasT
     , ToAliasReference(..)
     , ToAliasReferenceT
-    -- * The Normal Stuff
-    , module Database.Esqueleto
-    )
-    where
+    , ToSqlSetOperation(..)
 
-import Database.Esqueleto hiding (from, on, From(..))
-import qualified Control.Monad.Trans.Writer as W
-import qualified Control.Monad.Trans.State as S
-import Control.Monad.Trans.Class (lift)
-#if __GLASGOW_HASKELL__ < 804
-import Data.Semigroup
-#endif
-import Data.Proxy (Proxy(..))
+    -- * The Normal Stuff
+    , where_
+    , groupBy
+    , orderBy
+    , rand
+    , asc
+    , desc
+    , limit
+    , offset
+
+    , distinct
+    , distinctOn
+    , don
+    , distinctOnOrderBy
+    , having
+    , locking
+
+    , sub_select
+    , (^.)
+    , (?.)
+
+    , val
+    , isNothing
+    , just
+    , nothing
+    , joinV
+    , withNonNull
+
+    , countRows
+    , count
+    , countDistinct
+
+    , not_
+    , (==.)
+    , (>=.)
+    , (>.)
+    , (<=.)
+    , (<.)
+    , (!=.)
+    , (&&.)
+    , (||.)
+
+    , between
+    , (+.)
+    , (-.)
+    , (/.)
+    , (*.)
+
+    , random_
+    , round_
+    , ceiling_
+    , floor_
+
+    , min_
+    , max_
+    , sum_
+    , avg_
+    , castNum
+    , castNumM
+
+    , coalesce
+    , coalesceDefault
+
+    , lower_
+    , upper_
+    , trim_
+    , ltrim_
+    , rtrim_
+    , length_
+    , left_
+    , right_
+
+    , like
+    , ilike
+    , (%)
+    , concat_
+    , (++.)
+    , castString
+
+    , subList_select
+    , valList
+    , justList
+
+    , in_
+    , notIn
+    , exists
+    , notExists
+
+    , set
+    , (=.)
+    , (+=.)
+    , (-=.)
+    , (*=.)
+    , (/=.)
+
+    , case_
+    , toBaseId
+    , subSelect
+    , subSelectMaybe
+    , subSelectCount
+    , subSelectForeign
+    , subSelectList
+    , subSelectUnsafe
+    , ToBaseId(..)
+    , when_
+    , then_
+    , else_
+    , Value(..)
+    , ValueList(..)
+    , OrderBy
+    , DistinctOn
+    , LockingKind(..)
+    , SqlString
+
+      -- ** Joins
+    , InnerJoin(..)
+    , CrossJoin(..)
+    , LeftOuterJoin(..)
+    , RightOuterJoin(..)
+    , FullOuterJoin(..)
+    , JoinKind(..)
+    , OnClauseWithoutMatchingJoinException(..)
+
+      -- ** SQL backend
+    , SqlQuery
+    , SqlExpr
+    , SqlEntity
+    , select
+    , selectOne
+    , selectSource
+    , delete
+    , deleteCount
+    , update
+    , updateCount
+    , insertSelect
+    , insertSelectCount
+    , (<#)
+    , (<&>)
+
+    -- ** Rendering Queries
+    , renderQueryToText
+    , renderQuerySelect
+    , renderQueryUpdate
+    , renderQueryDelete
+    , renderQueryInsertInto
+
+    -- ** Helpers
+    , valkey
+    , valJ
+    , associateJoin
+
+      -- ** Re-exports
+      -- $reexports
+    , deleteKey
+    , module Database.Esqueleto.Internal.PersistentImport
+    ) where
+
+import Database.Esqueleto.Internal.Internal hiding (From, from, on)
 import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Internal
-          ( SqlExpr(..)
-          , InnerJoin(..)
-          , CrossJoin(..)
-          , LeftOuterJoin(..)
-          , RightOuterJoin(..)
-          , FullOuterJoin(..)
-          , FromClause(..)
-          , SqlQuery(..)
-          , SideData(..)
-          , Value(..)
-          , JoinKind(..)
-          , newIdentFor
-          , SqlSelect(..)
-          , Mode(..)
-          , toRawSql
-          , Ident(..)
-          , to3, to4, to5, to6, to7, to8
-          , from3, from4, from5, from6, from7, from8
-          , veryUnsafeCoerceSqlExprValue
-          , parensM
-          , NeedParens(..)
-          )
-import GHC.TypeLits
+
+import Database.Esqueleto.Experimental.From
+import Database.Esqueleto.Experimental.From.CommonTableExpression
+import Database.Esqueleto.Experimental.From.Join
+import Database.Esqueleto.Experimental.From.SqlSetOperation
+import Database.Esqueleto.Experimental.ToAlias
+import Database.Esqueleto.Experimental.ToAliasReference
+import Database.Esqueleto.Experimental.ToMaybe
 
 -- $setup
 --
@@ -95,9 +241,11 @@ import GHC.TypeLits
 --
 -- ...
 --
--- import Database.Esqueleto hiding (on, from)
 -- import Database.Esqueleto.Experimental
 -- @
+--
+-- Note: Prior to @esqueleto-3.3.4.0@, the @Database.Esqueleto.Experimental@
+-- module did not reexport @Data.Esqueleto@.
 
 ----------------------------------------------------------------------
 
@@ -170,7 +318,7 @@ import GHC.TypeLits
 --
 -- @
 -- select $ do
--- people <- from $ Table \@Person
+-- people <- from $ table \@Person
 -- where_ (people ^. PersonName ==. val \"John\")
 -- pure people
 -- @
@@ -198,8 +346,8 @@ import GHC.TypeLits
 -- @
 -- select $ do
 -- (people :& blogPosts) <-
---     from $ Table \@Person
---     \`LeftOuterJoin\` Table \@BlogPost
+--     from $ table \@Person
+--     \`leftJoin\` table \@BlogPost
 --     \`on\` (\\(people :& blogPosts) ->
 --             people ^. PersonId ==. blogPosts ?. BlogPostAuthorId)
 -- where_ (people ^. PersonAge >. val 18)
@@ -230,7 +378,7 @@ import GHC.TypeLits
 --
 -- In this version, with each successive 'on' clause, only the tables
 -- we have already joined into are in scope, so we must pattern match
--- accordingly. In this case, in the second 'InnerJoin', we do not use
+-- accordingly. In this case, in the second 'innerJoin', we do not use
 -- the first `Person` reference, so we use @_@ as a placeholder to
 -- ignore it. This prevents a possible runtime error where a table
 -- is referenced before it appears in the sequence of 'JOIN's.
@@ -238,11 +386,11 @@ import GHC.TypeLits
 -- @
 -- select $ do
 -- (people1 :& followers :& people2) <-
---     from $ Table \@Person
---     \`InnerJoin` Table \@Follow
+--     from $ table \@Person
+--     \`innerJoin` table \@Follow
 --     \`on\` (\\(people1 :& followers) ->
 --             people1 ^. PersonId ==. followers ^. FollowFollowed)
---     \`InnerJoin` Table \@Person
+--     \`innerJoin` table \@Person
 --     \`on\` (\\(_ :& followers :& people2) ->
 --             followers ^. FollowFollower ==. people2 ^. PersonId)
 -- where_ (people1 ^. PersonName ==. val \"John\")
@@ -272,10 +420,10 @@ import GHC.TypeLits
 -- @
 -- select $ do
 -- peopleWithPosts <-
---   from $ SelectQuery $ do
+--   from $ do
 --     (people :& blogPosts) <-
---       from $ Table \@Person
---       \`InnerJoin\` Table \@BlogPost
+--       from $ table \@Person
+--       \`innerJoin\` table \@BlogPost
 --       \`on\` (\\(p :& bP) ->
 --               p ^. PersonId ==. bP ^. BlogPostAuthorId)
 --     groupBy (people ^. PersonId)
@@ -303,23 +451,23 @@ import GHC.TypeLits
 -- @
 -- select $ do
 -- (authors, blogPosts) <- from $
---   (SelectQuery $ do
+--   (do
 --     (author :& blogPost) <-
---       from $ Table \@Person
---       \`InnerJoin\` Table \@BlogPost
+--       from $ table \@Person
+--       \`innerJoin\` table \@BlogPost
 --       \`on\` (\\(a :& bP) ->
 --               a ^. PersonId ==. bP ^. BlogPostAuthorId)
 --     where_ (author ^. PersonId ==. val currentPersonId)
 --     pure (author, blogPost)
 --   )
---   \`Union\`
---   (SelectQuery $ do
+--   \`union_\`
+--   (do
 --     (follow :& blogPost :& author) <-
---       from $ Table \@Follow
---       \`InnerJoin\` Table \@BlogPost
+--       from $ table \@Follow
+--       \`innerJoin\` table \@BlogPost
 --       \`on\` (\\(f :& bP) ->
 --               f ^. FollowFollowed ==. bP ^. BlogPostAuthorId)
---       \`InnerJoin\` Table \@Person
+--       \`innerJoin\` table \@Person
 --       \`on\` (\\(_ :& bP :& a) ->
 --               bP ^. BlogPostAuthorId ==. a ^. PersonId)
 --     where_ (follow ^. FollowFollower ==. val currentPersonId)
@@ -329,551 +477,87 @@ import GHC.TypeLits
 -- limit 25
 -- pure (authors, blogPosts)
 -- @
-
--- | A left-precedence pair. Pronounced \"and\". Used to represent expressions
--- that have been joined together.
 --
--- The precedence behavior can be demonstrated by:
+-- === Example 6: LATERAL JOIN
+--
+-- As of version @3.4.0.0@, lateral subquery joins are supported.
+--
 --
 -- @
--- a :& b :& c == ((a :& b) :& c)
+-- select $ do
+-- (salesPerson :& maxSaleAmount :& maxSaleCustomerName) <-
+--   from $ table \@SalesPerson
+--   \`crossJoinLateral\` (\\salesPerson -> do
+--         sales <- from $ table \@Sale
+--         where_ $ sales ^. SaleSalesPersonId ==. salesPerson ^. SalesPersonId
+--         pure $ max_ (sales ^. SaleAmount)
+--         )
+--   \`crossJoinLateral\` (\\(salesPerson :& maxSaleAmount) -> do
+--         sales <- from $ table \@Sale
+--         where_ $ sales ^. SaleSalesPersonId ==. salesPerson ^. SalesPersonId
+--              &&. sales ^. SaleAmount ==. maxSaleAmount
+--         pure $ sales ^. SaleCustomerName)
+--         )
+-- pure (salesPerson ^. SalesPersonName, maxSaleAmount, maxSaleCustomerName)
 -- @
 --
--- See the examples at the beginning of this module to see how this
--- operator is used in 'JOIN' operations.
-data (:&) a b = a :& b
-infixl 2 :&
-
--- | Data type that represents SQL set operations. This includes
--- 'UNION', 'UNION' 'ALL', 'EXCEPT', and 'INTERSECT'. This data
--- type is defined as a binary tree, with @SelectQuery@ on the leaves.
+-- This is the equivalent to the following SQL (example taken from the
+-- [MySQL Lateral Derived Table](https://dev.mysql.com/doc/refman/8.0/en/lateral-derived-tables.html)
+-- documentation):
 --
--- Each constructor corresponding to the aforementioned set operations
--- can be used as an infix function in a @from@ to help with readability
+-- @
+-- SELECT
+--   salesperson.name,
+--   max_sale.amount,
+--   max_sale_customer.customer_name
+-- FROM
+--   salesperson,
+--   -- calculate maximum size, cache it in transient derived table max_sale
+--   LATERAL
+--   (SELECT MAX(amount) AS amount
+--     FROM all_sales
+--     WHERE all_sales.salesperson_id = salesperson.id)
+--   AS max_sale,
+--   LATERAL
+--   (SELECT customer_name
+--     FROM all_sales
+--     WHERE all_sales.salesperson_id = salesperson.id
+--     AND all_sales.amount =
+--         -- the cached maximum size
+--         max_sale.amount)
+--   AS max_sale_customer;
+-- @
+
+-- $sql-set-operations
+--
+-- Data type that represents SQL set operations. This includes
+-- 'UNION', 'UNION' 'ALL', 'EXCEPT', and 'INTERSECT'. These types form
+-- a binary tree, with @SqlQuery@ values on the leaves.
+--
+-- Each function corresponding to the aforementioned set operations
+-- can be used as an infix in a @from@ to help with readability
 -- and lead to code that closely resembles the underlying SQL. For example,
 --
 -- @
 -- select $ from $
---   (SelectQuery ...)
---   \`Union\`
---   (SelectQuery ...)
+--   (do
+--      a <- from $ table @A
+--      pure $ a ^. ASomeCol
+--   )
+--   \`union_\`
+--   (do
+--      b <- from $ table @B
+--      pure $ b ^. BSomeCol
+--   )
 -- @
 --
 -- is translated into
 --
 -- @
 -- SELECT * FROM (
---   (SELECT * FROM ...)
+--   (SELECT a.some_col FROM a)
 --   UNION
---   (SELECT * FROM ...)
+--   (SELECT b.some_col FROM b)
 -- )
 -- @
 --
--- @SelectQuery@ can be used without any of the set operations to construct
--- a subquery. This can be used in 'JOIN' trees. For example,
---
--- @
--- select $ from $
---   Table \@SomeTable
---   \`InnerJoin\` (SelectQuery ...)
---   \`on\` ...
--- @
---
--- is translated into
---
--- @
--- SELECT *
--- FROM SomeTable
--- INNER JOIN (SELECT * FROM ...)
--- ON ...
--- @
-data SqlSetOperation a =
-    Union (SqlSetOperation a) (SqlSetOperation a)
-  | UnionAll (SqlSetOperation a) (SqlSetOperation a)
-  | Except (SqlSetOperation a) (SqlSetOperation a)
-  | Intersect (SqlSetOperation a) (SqlSetOperation a)
-  | SelectQueryP NeedParens (SqlQuery a)
-
-pattern SelectQuery :: SqlQuery a -> SqlSetOperation a
-pattern SelectQuery q = SelectQueryP Never q
-
--- | Data type that represents the syntax of a 'JOIN' tree. In practice,
--- only the @Table@ constructor is used directly when writing queries. For example,
---
--- @
--- select $ from $ Table \@People
--- @
-data From a where
-  Table         :: PersistEntity ent => From (SqlExpr (Entity ent))
-  SubQuery      :: (SqlSelect a' r, SqlSelect a'' r', ToAlias a, a' ~ ToAliasT a, ToAliasReference a', ToAliasReferenceT a' ~ a'')
-                => SqlQuery a
-                -> From a''
-  SqlSetOperation :: (SqlSelect a' r, ToAlias a, a' ~ ToAliasT a, ToAliasReference a', ToAliasReferenceT a' ~ a'')
-                  => SqlSetOperation a
-                  -> From a''
-  InnerJoinFrom :: From a
-                -> (From b, (a :& b) -> SqlExpr (Value Bool))
-                -> From (a :& b)
-  CrossJoinFrom :: From a
-                -> From b
-                -> From (a :& b)
-  LeftJoinFrom  :: ToMaybe b
-                => From a
-                -> (From b, (a :& ToMaybeT b) -> SqlExpr (Value Bool))
-                -> From (a :& ToMaybeT b)
-  RightJoinFrom :: ToMaybe a
-                => From a
-                -> (From b, (ToMaybeT a :& b) -> SqlExpr (Value Bool))
-                -> From (ToMaybeT a :& b)
-  FullJoinFrom  :: (ToMaybe a, ToMaybe b )
-                => From a
-                -> (From b, (ToMaybeT a :& ToMaybeT b) -> SqlExpr (Value Bool))
-                -> From (ToMaybeT a :& ToMaybeT b)
-
--- | An @ON@ clause that describes how two tables are related. This should be
--- used as an infix operator after a 'JOIN'. For example,
---
--- @
--- select $
--- from $ Table \@Person
--- \`InnerJoin\` Table \@BlogPost
--- \`on\` (\\(p :& bP) ->
---         p ^. PersonId ==. bP ^. BlogPostAuthorId)
--- @
---
-on :: ToFrom a => a -> (b -> SqlExpr (Value Bool)) -> (a, b -> SqlExpr (Value Bool))
-on = (,)
-infix 9 `on`
-
-type JoinErrorMsg jk = 'Text "Missing on statement for " ':<>: 'Text jk
-
-type family ToFromT a where
-  ToFromT (From a) = a
-  ToFromT (SqlSetOperation a) = ToAliasReferenceT (ToAliasT a)
-  ToFromT (LeftOuterJoin a (b, c -> SqlExpr (Value Bool))) = c
-  ToFromT (FullOuterJoin a (b, c -> SqlExpr (Value Bool))) = c
-  ToFromT (RightOuterJoin a (b, c -> SqlExpr (Value Bool))) = c
-  ToFromT (InnerJoin a (b, c -> SqlExpr (Value Bool))) = c
-  ToFromT (CrossJoin a b) = (ToFromT a :& ToFromT b)
-  ToFromT (InnerJoin a b) = TypeError (JoinErrorMsg "InnerJoin")
-  ToFromT (LeftOuterJoin a b) = TypeError (JoinErrorMsg "LeftOuterJoin")
-  ToFromT (RightOuterJoin a b) = TypeError (JoinErrorMsg "RightOuterJoin")
-  ToFromT (FullOuterJoin a b) = TypeError (JoinErrorMsg "FullOuterJoin")
-
-{-- Type class magic to allow the use of the `InnerJoin` family of data constructors in from --}
-class ToFrom a where
-  toFrom :: a -> From (ToFromT a)
-
-instance ToFrom (From a) where
-  toFrom = id
-
-instance {-# OVERLAPPABLE #-} ToFrom (InnerJoin a b) where
-  toFrom = undefined
-instance {-# OVERLAPPABLE #-} ToFrom (LeftOuterJoin a b) where
-  toFrom = undefined
-instance {-# OVERLAPPABLE #-} ToFrom (RightOuterJoin a b) where
-  toFrom = undefined
-instance {-# OVERLAPPABLE #-} ToFrom (FullOuterJoin a b) where
-  toFrom = undefined
-
-instance (SqlSelect a' r,SqlSelect a'' r', ToAlias a, a' ~ ToAliasT a, ToAliasReference a', ToAliasReferenceT a' ~ a'')  => ToFrom (SqlSetOperation a) where
-  -- If someone uses just a plain SelectQuery it should behave like a normal subquery
-  toFrom (SelectQueryP _ q) = SubQuery q
-  -- Otherwise use the SqlSetOperation
-  toFrom q = SqlSetOperation q
-
-instance (ToFrom a, ToFromT a ~ a', ToFrom b, ToFromT b ~ b', ToMaybe b', mb ~ ToMaybeT b')
-       => ToFrom (LeftOuterJoin a (b, (a' :& mb) -> SqlExpr (Value Bool))) where
-  toFrom (LeftOuterJoin lhs (rhs, on')) = LeftJoinFrom (toFrom lhs) (toFrom rhs, on')
-
-instance (ToFrom a, ToFromT a ~ a', ToFrom b, ToFromT b ~ b', ToMaybe a', ma ~ ToMaybeT a', ToMaybe b', mb ~ ToMaybeT b')
-       => ToFrom (FullOuterJoin a (b, (ma :& mb) -> SqlExpr (Value Bool))) where
-  toFrom (FullOuterJoin lhs (rhs, on')) = FullJoinFrom (toFrom lhs) (toFrom rhs, on')
-
-instance (ToFrom a, ToFromT a ~ a', ToFrom b, ToFromT b ~ b', ToMaybe a', ma ~ ToMaybeT a')
-       => ToFrom (RightOuterJoin a (b, (ma :& b') -> SqlExpr (Value Bool))) where
-  toFrom (RightOuterJoin lhs (rhs, on')) = RightJoinFrom (toFrom lhs) (toFrom rhs, on')
-
-instance (ToFrom a, ToFromT a ~ a', ToFrom b, ToFromT b ~ b') => ToFrom (InnerJoin a (b, (a' :& b') -> SqlExpr (Value Bool))) where
-  toFrom (InnerJoin lhs (rhs, on')) = InnerJoinFrom (toFrom lhs) (toFrom rhs, on')
-
-instance (ToFrom a, ToFrom b) => ToFrom (CrossJoin a b) where
-  toFrom (CrossJoin lhs rhs) = CrossJoinFrom (toFrom lhs) (toFrom rhs)
-
-type family Nullable a where
-  Nullable (Maybe a) = a
-  Nullable a =  a
-
-type family ToMaybeT a where
-  ToMaybeT (SqlExpr (Maybe a)) = SqlExpr (Maybe a)
-  ToMaybeT (SqlExpr (Entity a)) = SqlExpr (Maybe (Entity a))
-  ToMaybeT (SqlExpr (Value a)) = SqlExpr (Value (Maybe (Nullable a)))
-  ToMaybeT (a :& b) = (ToMaybeT a :& ToMaybeT b)
-  ToMaybeT (a, b) = (ToMaybeT a, ToMaybeT b)
-  ToMaybeT (a, b, c) = (ToMaybeT a, ToMaybeT b, ToMaybeT c)
-  ToMaybeT (a, b, c, d) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d)
-  ToMaybeT (a, b, c, d, e) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e)
-  ToMaybeT (a, b, c, d, e, f) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f)
-  ToMaybeT (a, b, c, d, e, f, g) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f, ToMaybeT g)
-  ToMaybeT (a, b, c, d, e, f, g, h) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f, ToMaybeT g, ToMaybeT h)
-
-class ToMaybe a where
-  toMaybe :: a -> ToMaybeT a
-
-instance ToMaybe (SqlExpr (Maybe a)) where
-  toMaybe = id
-
-instance ToMaybe (SqlExpr (Entity a)) where
-  toMaybe = EMaybe
-
-instance ToMaybe (SqlExpr (Value a)) where
-  toMaybe = veryUnsafeCoerceSqlExprValue
-
-instance (ToMaybe a, ToMaybe b) => ToMaybe (a :& b) where
-  toMaybe (a :& b) = (toMaybe a :& toMaybe b)
-
-instance (ToMaybe a, ToMaybe b) => ToMaybe (a,b) where
-  toMaybe (a, b) = (toMaybe a, toMaybe b)
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         ) => ToMaybe (a,b,c) where
-  toMaybe = to3 . toMaybe . from3
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         , ToMaybe d
-         ) => ToMaybe (a,b,c,d) where
-  toMaybe = to4 . toMaybe . from4
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         , ToMaybe d
-         , ToMaybe e
-         ) => ToMaybe (a,b,c,d,e) where
-  toMaybe = to5 . toMaybe . from5
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         , ToMaybe d
-         , ToMaybe e
-         , ToMaybe f
-         ) => ToMaybe (a,b,c,d,e,f) where
-  toMaybe = to6 . toMaybe . from6
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         , ToMaybe d
-         , ToMaybe e
-         , ToMaybe f
-         , ToMaybe g
-         ) => ToMaybe (a,b,c,d,e,f,g) where
-  toMaybe = to7 . toMaybe . from7
-
-instance ( ToMaybe a
-         , ToMaybe b
-         , ToMaybe c
-         , ToMaybe d
-         , ToMaybe e
-         , ToMaybe f
-         , ToMaybe g
-         , ToMaybe h
-         ) => ToMaybe (a,b,c,d,e,f,g,h) where
-  toMaybe = to8 . toMaybe . from8
-
--- | 'FROM' clause, used to bring entities into scope.
---
--- Internally, this function uses the `From` datatype and the
--- `ToFrom` typeclass. Unlike the old `Database.Esqueleto.from`,
--- this does not take a function as a parameter, but rather
--- a value that represents a 'JOIN' tree constructed out of
--- instances of `ToFrom`. This implementation eliminates certain
--- types of runtime errors by preventing the construction of
--- invalid SQL (e.g. illegal nested-@from@).
-from :: ToFrom a  => a -> SqlQuery (ToFromT a)
-from parts = do
-  (a, clause) <- runFrom $ toFrom parts
-  Q $ W.tell mempty{sdFromClause=[clause]}
-  pure a
-    where
-      runFrom :: From a -> SqlQuery (a, FromClause)
-      runFrom e@Table = do
-        let ed = entityDef $ getVal e
-        ident <- newIdentFor (entityDB ed)
-        let entity = EEntity ident
-        pure $ (entity, FromStart ident ed)
-          where
-            getVal :: PersistEntity ent => From (SqlExpr (Entity ent)) -> Proxy ent
-            getVal = const Proxy
-      runFrom (SubQuery subquery) = do
-          -- We want to update the IdentState without writing the query to side data
-          (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ subquery
-          aliasedValue <- toAlias ret
-          -- Make a fake query with the aliased results, this allows us to ensure that the query is only run once
-          let aliasedQuery = Q $ W.WriterT $ pure (aliasedValue, sideData)
-          -- Add the FromQuery that renders the subquery to our side data
-          subqueryAlias <- newIdentFor (DBName "q")
-          -- Pass the aliased results of the subquery to the outer query
-          -- create aliased references from the outer query results (e.g value from subquery will be `subquery`.`value`),
-          -- this is probably overkill as the aliases should already be unique but seems to be good practice.
-          ref <- toAliasReference subqueryAlias aliasedValue
-          pure (ref , FromQuery subqueryAlias (\info -> toRawSql SELECT info aliasedQuery))
-
-      runFrom (SqlSetOperation operation) = do
-          (aliasedOperation, ret) <- aliasQueries operation
-          ident <- newIdentFor (DBName "u")
-          ref <- toAliasReference ident ret
-          pure (ref, FromQuery ident $ operationToSql aliasedOperation)
-
-          where
-            aliasQueries o =
-              case o of
-                SelectQueryP p q -> do
-                  (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ q
-                  prevState <- Q $ lift S.get
-                  aliasedRet <- toAlias ret
-                  Q $ lift $ S.put prevState
-                  let p' =
-                        case p of
-                          Parens -> Parens
-                          Never ->
-                            if (sdLimitClause sideData) /= mempty
-                                || length (sdOrderByClause sideData) > 0 then
-                              Parens
-                            else
-                              Never
-                  pure (SelectQueryP p' $ Q $ W.WriterT $ pure (aliasedRet, sideData), aliasedRet)
-                Union     o1 o2 -> do
-                  (o1', ret) <- aliasQueries o1
-                  (o2', _  ) <- aliasQueries o2
-                  pure (Union o1' o2', ret)
-                UnionAll  o1 o2 -> do
-                  (o1', ret) <- aliasQueries o1
-                  (o2', _  ) <- aliasQueries o2
-                  pure (UnionAll o1' o2', ret)
-                Except    o1 o2 -> do
-                  (o1', ret) <- aliasQueries o1
-                  (o2', _  ) <- aliasQueries o2
-                  pure (Except o1' o2', ret)
-                Intersect o1 o2 -> do
-                  (o1', ret) <- aliasQueries o1
-                  (o2', _  ) <- aliasQueries o2
-                  pure (Intersect o1' o2', ret)
-
-            operationToSql o info =
-              case o of
-                SelectQueryP p q  ->
-                  let (builder, values) = toRawSql SELECT info q
-                  in (parensM p builder, values)
-                Union     o1 o2 -> doSetOperation "UNION"     info o1 o2
-                UnionAll  o1 o2 -> doSetOperation "UNION ALL" info o1 o2
-                Except    o1 o2 -> doSetOperation "EXCEPT"    info o1 o2
-                Intersect o1 o2 -> doSetOperation "INTERSECT" info o1 o2
-
-            doSetOperation operationText info o1 o2 =
-                  let
-                    (q1, v1) = operationToSql o1 info
-                    (q2, v2) = operationToSql o2 info
-                  in (q1 <> " " <> operationText <> " " <> q2, v1 <> v2)
-
-
-      runFrom (InnerJoinFrom leftPart (rightPart, on')) = do
-        (leftVal, leftFrom) <- runFrom leftPart
-        (rightVal, rightFrom) <- runFrom rightPart
-        let ret = leftVal :& rightVal
-        pure $ (ret, FromJoin leftFrom InnerJoinKind rightFrom (Just (on' ret)))
-      runFrom (CrossJoinFrom leftPart rightPart) = do
-        (leftVal, leftFrom) <- runFrom leftPart
-        (rightVal, rightFrom) <- runFrom rightPart
-        let ret = leftVal :& rightVal
-        pure $ (ret, FromJoin leftFrom CrossJoinKind rightFrom Nothing)
-      runFrom (LeftJoinFrom leftPart (rightPart, on')) = do
-        (leftVal, leftFrom) <- runFrom leftPart
-        (rightVal, rightFrom) <- runFrom rightPart
-        let ret = leftVal :& (toMaybe rightVal)
-        pure $ (ret, FromJoin leftFrom LeftOuterJoinKind rightFrom (Just (on' ret)))
-      runFrom (RightJoinFrom leftPart (rightPart, on')) = do
-        (leftVal, leftFrom) <- runFrom leftPart
-        (rightVal, rightFrom) <- runFrom rightPart
-        let ret = (toMaybe leftVal) :& rightVal
-        pure $ (ret, FromJoin leftFrom RightOuterJoinKind rightFrom (Just (on' ret)))
-      runFrom (FullJoinFrom leftPart (rightPart, on')) = do
-        (leftVal, leftFrom) <- runFrom leftPart
-        (rightVal, rightFrom) <- runFrom rightPart
-        let ret = (toMaybe leftVal) :& (toMaybe rightVal)
-        pure $ (ret, FromJoin leftFrom FullOuterJoinKind rightFrom (Just (on' ret)))
-
-type family ToAliasT a where
-  ToAliasT (SqlExpr (Value a)) = SqlExpr (Value a)
-  ToAliasT (SqlExpr (Entity a)) = SqlExpr (Entity a)
-  ToAliasT (SqlExpr (Maybe (Entity a))) = SqlExpr (Maybe (Entity a))
-  ToAliasT (a, b) = (ToAliasT a, ToAliasT b)
-  ToAliasT (a, b, c) = (ToAliasT a, ToAliasT b, ToAliasT c)
-  ToAliasT (a, b, c, d) = (ToAliasT a, ToAliasT b, ToAliasT c, ToAliasT d)
-  ToAliasT (a, b, c, d, e) = (ToAliasT a, ToAliasT b, ToAliasT c, ToAliasT d, ToAliasT e)
-  ToAliasT (a, b, c, d, e, f) = (ToAliasT a, ToAliasT b, ToAliasT c, ToAliasT d, ToAliasT e, ToAliasT f)
-  ToAliasT (a, b, c, d, e, f, g) = (ToAliasT a, ToAliasT b, ToAliasT c, ToAliasT d, ToAliasT e, ToAliasT f, ToAliasT g)
-  ToAliasT (a, b, c, d, e, f, g, h) = (ToAliasT a, ToAliasT b, ToAliasT c, ToAliasT d, ToAliasT e, ToAliasT f, ToAliasT g, ToAliasT h)
-
--- Tedious tuple magic
-class ToAlias a where
-  toAlias :: a -> SqlQuery (ToAliasT a)
-
-instance ToAlias (SqlExpr (Value a)) where
-  toAlias v@(EAliasedValue _ _) = pure v
-  toAlias v = do
-    ident <- newIdentFor (DBName "v")
-    pure $ EAliasedValue ident v
-
-instance ToAlias (SqlExpr (Entity a)) where
-  toAlias v@(EAliasedEntityReference _ _) = pure v
-  toAlias v@(EAliasedEntity _ _) = pure v
-  toAlias (EEntity tableIdent) = do
-    ident <- newIdentFor (DBName "v")
-    pure $ EAliasedEntity ident tableIdent
-
-instance ToAlias (SqlExpr (Maybe (Entity a))) where
-  toAlias (EMaybe e) = EMaybe <$> toAlias e
-
-instance (ToAlias a, ToAlias b) => ToAlias (a,b) where
-  toAlias (a,b) = (,) <$> toAlias a <*> toAlias b
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         ) => ToAlias (a,b,c) where
-  toAlias x = to3 <$> (toAlias $ from3 x)
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         , ToAlias d
-         ) => ToAlias (a,b,c,d) where
-  toAlias x = to4 <$> (toAlias $ from4 x)
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         , ToAlias d
-         , ToAlias e
-         ) => ToAlias (a,b,c,d,e) where
-  toAlias x = to5 <$> (toAlias $ from5 x)
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         , ToAlias d
-         , ToAlias e
-         , ToAlias f
-         ) => ToAlias (a,b,c,d,e,f) where
-  toAlias x = to6 <$> (toAlias $ from6 x)
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         , ToAlias d
-         , ToAlias e
-         , ToAlias f
-         , ToAlias g
-         ) => ToAlias (a,b,c,d,e,f,g) where
-  toAlias x = to7 <$> (toAlias $ from7 x)
-
-instance ( ToAlias a
-         , ToAlias b
-         , ToAlias c
-         , ToAlias d
-         , ToAlias e
-         , ToAlias f
-         , ToAlias g
-         , ToAlias h
-         ) => ToAlias (a,b,c,d,e,f,g,h) where
-  toAlias x = to8 <$> (toAlias $ from8 x)
-
-
-type family ToAliasReferenceT a where
-  ToAliasReferenceT (SqlExpr (Value a)) = SqlExpr (Value a)
-  ToAliasReferenceT (SqlExpr (Entity a)) = SqlExpr (Entity a)
-  ToAliasReferenceT (SqlExpr (Maybe (Entity a))) = SqlExpr (Maybe (Entity a))
-  ToAliasReferenceT (a,b) = (ToAliasReferenceT a, ToAliasReferenceT b)
-  ToAliasReferenceT (a,b,c) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c)
-  ToAliasReferenceT (a, b, c, d) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c, ToAliasReferenceT d)
-  ToAliasReferenceT (a, b, c, d, e) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c, ToAliasReferenceT d, ToAliasReferenceT e)
-  ToAliasReferenceT (a, b, c, d, e, f) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c, ToAliasReferenceT d, ToAliasReferenceT e, ToAliasReferenceT f)
-  ToAliasReferenceT (a, b, c, d, e, f, g) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c, ToAliasReferenceT d, ToAliasReferenceT e, ToAliasReferenceT f, ToAliasReferenceT g)
-  ToAliasReferenceT (a, b, c, d, e, f, g, h) = (ToAliasReferenceT a, ToAliasReferenceT b, ToAliasReferenceT c, ToAliasReferenceT d, ToAliasReferenceT e, ToAliasReferenceT f, ToAliasReferenceT g, ToAliasReferenceT h)
-
--- more tedious tuple magic
-class ToAliasReference a where
-  toAliasReference :: Ident -> a -> SqlQuery (ToAliasReferenceT a)
-
-instance ToAliasReference (SqlExpr (Value a)) where
-  toAliasReference aliasSource (EAliasedValue aliasIdent _) = pure $ EValueReference aliasSource (\_ -> aliasIdent)
-  toAliasReference _           v@(ERaw _ _)                 = toAlias v
-  toAliasReference _           v@(ECompositeKey _)          = toAlias v
-  toAliasReference s             (EValueReference _ b)      = pure $ EValueReference s b
-
-instance ToAliasReference (SqlExpr (Entity a)) where
-  toAliasReference aliasSource (EAliasedEntity ident _) = pure $ EAliasedEntityReference aliasSource ident
-  toAliasReference _ e@(EEntity _) = toAlias e
-  toAliasReference s   (EAliasedEntityReference _ b) = pure $ EAliasedEntityReference s b
-
-instance ToAliasReference (SqlExpr (Maybe (Entity a))) where
-  toAliasReference s (EMaybe e) = EMaybe <$> toAliasReference s e
-instance (ToAliasReference a, ToAliasReference b) => ToAliasReference (a, b) where
-  toAliasReference ident (a,b) = (,) <$> (toAliasReference ident a) <*> (toAliasReference ident b)
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         ) => ToAliasReference (a,b,c) where
-  toAliasReference ident x = fmap to3 $ toAliasReference ident $ from3 x
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         , ToAliasReference d
-         ) => ToAliasReference (a,b,c,d) where
-  toAliasReference ident x = fmap to4 $ toAliasReference ident $ from4 x
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         , ToAliasReference d
-         , ToAliasReference e
-         ) => ToAliasReference (a,b,c,d,e) where
-  toAliasReference ident x = fmap to5 $ toAliasReference ident $ from5 x
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         , ToAliasReference d
-         , ToAliasReference e
-         , ToAliasReference f
-         ) => ToAliasReference (a,b,c,d,e,f) where
-  toAliasReference ident x = to6 <$> (toAliasReference ident $ from6 x)
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         , ToAliasReference d
-         , ToAliasReference e
-         , ToAliasReference f
-         , ToAliasReference g
-         ) => ToAliasReference (a,b,c,d,e,f,g) where
-  toAliasReference ident x = to7 <$> (toAliasReference ident $ from7 x)
-
-instance ( ToAliasReference a
-         , ToAliasReference b
-         , ToAliasReference c
-         , ToAliasReference d
-         , ToAliasReference e
-         , ToAliasReference f
-         , ToAliasReference g
-         , ToAliasReference h
-         ) => ToAliasReference (a,b,c,d,e,f,g,h) where
-  toAliasReference ident x = to8 <$> (toAliasReference ident $ from8 x)

src/Database/Esqueleto/Experimental/From.hs

@@ -0,0 +1,145 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Database.Esqueleto.Experimental.From
+    where
+
+import qualified Control.Monad.Trans.Writer as W
+import Data.Coerce (coerce)
+import Data.Proxy
+import qualified Data.Text.Lazy.Builder as TLB
+import Database.Esqueleto.Experimental.ToAlias
+import Database.Esqueleto.Experimental.ToAliasReference
+import Database.Esqueleto.Internal.Internal hiding (From(..), from, on)
+import Database.Esqueleto.Internal.PersistentImport
+
+import Database.Persist.Names (EntityNameDB(..))
+
+-- | 'FROM' clause, used to bring entities into scope.
+--
+-- Internally, this function uses the `From` datatype.
+-- Unlike the old `Database.Esqueleto.from`, this does not
+-- take a function as a parameter, but rather a value that
+-- represents a 'JOIN' tree constructed out of instances of `From`.
+-- This implementation eliminates certain
+-- types of runtime errors by preventing the construction of
+-- invalid SQL (e.g. illegal nested-@from@).
+from :: ToFrom a a' => a -> SqlQuery a'
+from f = do
+    (a, clause) <- unFrom (toFrom f)
+    Q $ W.tell mempty{sdFromClause=[FromRaw $ clause]}
+    pure a
+
+type RawFn = NeedParens -> IdentInfo -> (TLB.Builder, [PersistValue])
+
+-- | Data type defining the "From" language. This should not
+-- constructed directly in application code.
+--
+-- A @From@ is a SqlQuery which returns a reference to the result of calling from
+-- and a function that produces a portion of a FROM clause. This gets passed to
+-- the FromRaw FromClause constructor directly when converting
+-- from a @From@ to a @SqlQuery@ using @from@
+--
+-- @since 3.5.0.0
+newtype From a = From
+    { unFrom :: SqlQuery (a, RawFn)}
+
+
+-- | A helper class primarily designed to allow using @SqlQuery@ directly in
+-- a From expression. This is also useful for embedding a @SqlSetOperation@,
+-- as well as supporting backwards compatibility for the
+-- data constructor join tree used prior to /3.5.0.0/
+--
+-- @since 3.5.0.0
+class ToFrom a r | a -> r where
+    toFrom :: a -> From r
+instance ToFrom (From a) a where
+    toFrom = id
+
+{-# DEPRECATED Table "@since 3.5.0.0 - use 'table' instead" #-}
+data Table a = Table
+
+instance PersistEntity ent => ToFrom (Table ent) (SqlExpr (Entity ent)) where
+    toFrom _ = table
+
+-- | Bring a PersistEntity into scope from a table
+--
+-- @
+-- select $ from $ table \@People
+-- @
+--
+-- @since 3.5.0.0
+table :: forall ent. PersistEntity ent => From (SqlExpr (Entity ent))
+table = From $ do
+    let ed = entityDef (Proxy @ent)
+    ident <- newIdentFor (coerce $ getEntityDBName ed)
+    let entity = unsafeSqlEntity ident
+    pure $ ( entity, const $ base ident ed )
+      where
+        base ident@(I identText) def info =
+            let db = coerce $ getEntityDBName def
+            in ( (fromDBName info (coerce db)) <>
+                     if  db == identText
+                     then mempty
+                     else " AS " <> useIdent info ident
+               , mempty
+               )
+
+
+{-# DEPRECATED SubQuery "/Since: 3.4.0.0/ - It is no longer necessary to tag 'SqlQuery' values with @SubQuery@" #-}
+newtype SubQuery a = SubQuery a
+instance (SqlSelect a r, ToAlias a, ToAliasReference a) => ToFrom (SubQuery (SqlQuery a)) a where
+    toFrom (SubQuery q) = selectQuery q
+instance (SqlSelect a r, ToAlias a, ToAliasReference a) => ToFrom (SqlQuery a) a where
+    toFrom = selectQuery
+
+-- | Select from a subquery, often used in conjuction with joins but can be
+-- used without any joins. Because @SqlQuery@ has a @ToFrom@ instance you probably
+-- dont need to use this function directly.
+--
+-- @
+-- select $
+--      p <- from $
+--              selectQuery do
+--              p <- from $ table \@Person
+--              limit 5
+--              orderBy [ asc p ^. PersonAge ]
+--      ...
+-- @
+--
+-- @since 3.5.0.0
+selectQuery :: (SqlSelect a r, ToAlias a, ToAliasReference a) => SqlQuery a -> From a
+selectQuery subquery = From $ do
+    -- We want to update the IdentState without writing the query to side data
+    (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ subquery
+    aliasedValue <- toAlias ret
+    -- Make a fake query with the aliased results, this allows us to ensure that the query is only run once
+    let aliasedQuery = Q $ W.WriterT $ pure (aliasedValue, sideData)
+    -- Add the FromQuery that renders the subquery to our side data
+    subqueryAlias <- newIdentFor (DBName "q")
+    -- Pass the aliased results of the subquery to the outer query
+    -- create aliased references from the outer query results (e.g value from subquery will be `subquery`.`value`),
+    -- this is probably overkill as the aliases should already be unique but seems to be good practice.
+    ref <- toAliasReference subqueryAlias aliasedValue
+
+    pure (ref, \_ info ->
+            let (queryText,queryVals) = toRawSql SELECT info aliasedQuery
+            in
+            ( (parens queryText) <> " AS " <> useIdent info subqueryAlias
+            , queryVals
+            )
+         )

src/Database/Esqueleto/Experimental/From/CommonTableExpression.hs

@@ -0,0 +1,111 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module Database.Esqueleto.Experimental.From.CommonTableExpression
+    where
+
+import qualified Control.Monad.Trans.Writer as W
+import qualified Data.Text.Lazy.Builder as TLB
+import Database.Esqueleto.Experimental.From
+import Database.Esqueleto.Experimental.From.SqlSetOperation
+import Database.Esqueleto.Experimental.ToAlias
+import Database.Esqueleto.Experimental.ToAliasReference
+import Database.Esqueleto.Internal.Internal hiding (From(..), from, on)
+
+-- | @WITH@ clause used to introduce a [Common Table Expression (CTE)](https://en.wikipedia.org/wiki/Hierarchical_and_recursive_queries_in_SQL#Common_table_expression).
+-- CTEs are supported in most modern SQL engines and can be useful
+-- in performance tuning. In Esqueleto, CTEs should be used as a
+-- subquery memoization tactic. When writing plain SQL, CTEs
+-- are sometimes used to organize the SQL code, in Esqueleto, this
+-- is better achieved through function that return 'SqlQuery' values.
+--
+-- @
+-- select $ do
+-- cte <- with subQuery
+-- cteResult <- from cte
+-- where_ $ cteResult ...
+-- pure cteResult
+-- @
+--
+-- __WARNING__: In some SQL engines using a CTE can diminish performance.
+-- In these engines the CTE is treated as an optimization fence. You should
+-- always verify that using a CTE will in fact improve your performance
+-- over a regular subquery.
+--
+-- /Since: 3.4.0.0/
+with :: ( ToAlias a
+        , ToAliasReference a
+        , SqlSelect a r
+        ) => SqlQuery a -> SqlQuery (From a)
+with query = do
+    (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ query
+    aliasedValue <- toAlias ret
+    let aliasedQuery = Q $ W.WriterT $ pure (aliasedValue, sideData)
+    ident <- newIdentFor (DBName "cte")
+    let clause = CommonTableExpressionClause NormalCommonTableExpression ident (\info -> toRawSql SELECT info aliasedQuery)
+    Q $ W.tell mempty{sdCteClause = [clause]}
+    ref <- toAliasReference ident aliasedValue
+    pure $ From $ pure (ref, (\_ info -> (useIdent info ident, mempty)))
+
+-- | @WITH@ @RECURSIVE@ allows one to make a recursive subquery, which can
+-- reference itself. Like @WITH@, this is supported in most modern SQL engines.
+-- Useful for hierarchical, self-referential data, like a tree of data.
+--
+-- @
+-- select $ do
+-- cte <- withRecursive
+--          (do
+--              person <- from $ table \@Person
+--              where_ $ person ^. PersonId ==. val personId
+--              pure person
+--          )
+--          unionAll_
+--          (\\self -> do
+--              (p :& f :& p2 :& pSelf) <- from self
+--                       \`innerJoin\` $ table \@Follow
+--                       \`on\` (\\(p :& f) ->
+--                               p ^. PersonId ==. f ^. FollowFollower)
+--                       \`innerJoin\` $ table \@Person
+--                       \`on\` (\\(p :& f :& p2) ->
+--                               f ^. FollowFollowed ==. p2 ^. PersonId)
+--                       \`leftJoin\` self
+--                       \`on\` (\\(_ :& _ :& p2 :& pSelf) ->
+--                               just (p2 ^. PersonId) ==. pSelf ?. PersonId)
+--              where_ $ isNothing (pSelf ?. PersonId)
+--              groupBy (p2 ^. PersonId)
+--              pure p2
+--          )
+-- from cte
+-- @
+--
+-- /Since: 3.4.0.0/
+withRecursive :: ( ToAlias a
+                 , ToAliasReference a
+                 , SqlSelect a r
+                 )
+              => SqlQuery a
+              -> UnionKind
+              -> (From a -> SqlQuery a)
+              -> SqlQuery (From a)
+withRecursive baseCase unionKind recursiveCase = do
+    (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ baseCase
+    aliasedValue <- toAlias ret
+    let aliasedQuery = Q $ W.WriterT $ pure (aliasedValue, sideData)
+    ident <- newIdentFor (DBName "cte")
+    ref <- toAliasReference ident aliasedValue
+    let refFrom = From (pure (ref, (\_ info -> (useIdent info ident, mempty))))
+    let recursiveQuery = recursiveCase refFrom
+    let clause = CommonTableExpressionClause RecursiveCommonTableExpression ident
+                 (\info -> (toRawSql SELECT info aliasedQuery)
+                        <> ("\n" <> (unUnionKind unionKind)  <> "\n", mempty)
+                        <> (toRawSql SELECT info recursiveQuery)
+                 )
+    Q $ W.tell mempty{sdCteClause = [clause]}
+    pure refFrom
+
+newtype UnionKind = UnionKind { unUnionKind :: TLB.Builder }
+instance Union_ UnionKind where
+    union_ = UnionKind "UNION"
+instance UnionAll_ UnionKind where
+    unionAll_ = UnionKind "UNION ALL"

src/Database/Esqueleto/Experimental/From/Join.hs

@@ -0,0 +1,425 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Database.Esqueleto.Experimental.From.Join
+    where
+
+import Data.Bifunctor (first)
+import Data.Kind (Constraint)
+import Data.Proxy
+import qualified Data.Text.Lazy.Builder as TLB
+import Database.Esqueleto.Experimental.From
+import Database.Esqueleto.Experimental.ToAlias
+import Database.Esqueleto.Experimental.ToAliasReference
+import Database.Esqueleto.Experimental.ToMaybe
+import Database.Esqueleto.Internal.Internal hiding
+       (From(..), from, fromJoin, on)
+import GHC.TypeLits
+
+-- | A left-precedence pair. Pronounced \"and\". Used to represent expressions
+-- that have been joined together.
+--
+-- The precedence behavior can be demonstrated by:
+--
+-- @
+-- a :& b :& c == ((a :& b) :& c)
+-- @
+--
+-- See the examples at the beginning of this module to see how this
+-- operator is used in 'JOIN' operations.
+data (:&) a b = a :& b
+infixl 2 :&
+
+instance (ToMaybe a, ToMaybe b) => ToMaybe (a :& b) where
+    type ToMaybeT (a :& b) = (ToMaybeT a :& ToMaybeT b)
+    toMaybe (a :& b) = (toMaybe a :& toMaybe b)
+
+class ValidOnClause a
+instance {-# OVERLAPPABLE #-} ToFrom a a' => ValidOnClause a
+instance ValidOnClause (a -> SqlQuery b)
+
+-- | You may return joined values from a 'select' query - this is
+-- identical to the tuple instance, but is provided for convenience.
+--
+-- @since 3.5.2.0
+instance (SqlSelect a ra, SqlSelect b rb) => SqlSelect (a :& b) (ra :& rb) where
+    sqlSelectCols esc (a :& b) = sqlSelectCols esc (a, b)
+    sqlSelectColCount = sqlSelectColCount . toTuple
+      where
+        toTuple :: Proxy (a :& b) -> Proxy (a, b)
+        toTuple = const Proxy
+    sqlSelectProcessRow = fmap (uncurry (:&)) . sqlSelectProcessRow
+
+-- | Identical to the tuple instance and provided for convenience.
+--
+-- @since 3.5.3.0
+instance (ToAlias a, ToAlias b) => ToAlias (a :& b) where
+    toAlias (a :& b) = (:&) <$> toAlias a <*> toAlias b
+
+-- | Identical to the tuple instance and provided for convenience.
+--
+-- @since 3.5.3.0
+instance (ToAliasReference a, ToAliasReference b) => ToAliasReference (a :& b) where
+    toAliasReference ident (a :& b) = (:&) <$> (toAliasReference ident a) <*> (toAliasReference ident b)
+
+-- | An @ON@ clause that describes how two tables are related. This should be
+-- used as an infix operator after a 'JOIN'. For example,
+--
+-- @
+-- select $
+-- from $ table \@Person
+-- \`innerJoin\` table \@BlogPost
+-- \`on\` (\\(p :& bP) ->
+--         p ^. PersonId ==. bP ^. BlogPostAuthorId)
+-- @
+on :: ValidOnClause a => a -> (b -> SqlExpr (Value Bool)) -> (a, b -> SqlExpr (Value Bool))
+on = (,)
+infix 9 `on`
+
+type family ErrorOnLateral a :: Constraint where
+  ErrorOnLateral (a -> SqlQuery b) = TypeError ('Text "LATERAL can only be used for INNER, LEFT, and CROSS join kinds.")
+  ErrorOnLateral _ = ()
+
+fromJoin :: TLB.Builder -> RawFn -> RawFn -> Maybe (SqlExpr (Value Bool)) -> RawFn
+fromJoin joinKind lhs rhs monClause =
+    \paren info ->
+        first (parensM paren) $
+        mconcat [ lhs Never info
+                , (joinKind, mempty)
+                , rhs Parens info
+                , maybe mempty (makeOnClause info) monClause
+                ]
+    where
+        makeOnClause info (ERaw _ f)        = first (" ON " <>) (f Never info)
+
+type family HasOnClause actual expected :: Constraint where
+    HasOnClause (a, b -> SqlExpr (Value Bool)) c = () -- Let the compiler handle the type mismatch
+    HasOnClause a expected =
+        TypeError ( 'Text "Missing ON clause for join with"
+                    ':$$: 'ShowType a
+                    ':$$: 'Text ""
+                    ':$$: 'Text "Expected: "
+                    ':$$: 'ShowType a
+                    ':$$: 'Text "`on` " ':<>: 'ShowType (expected -> SqlExpr (Value Bool))
+                    ':$$: 'Text ""
+                  )
+
+
+-- | INNER JOIN
+--
+-- Used as an infix operator \`innerJoin\`
+--
+-- @
+-- select $
+-- from $ table \@Person
+-- \`innerJoin\` table \@BlogPost
+-- \`on\` (\\(p :& bp) ->
+--         p ^. PersonId ==. bp ^. BlogPostAuthorId)
+-- @
+--
+-- @since 3.5.0.0
+innerJoin :: ( ToFrom a a'
+             , ToFrom b b'
+             , HasOnClause rhs (a' :& b')
+             , rhs ~ (b, (a' :& b') -> SqlExpr (Value Bool))
+             ) => a -> rhs -> From (a' :& b')
+innerJoin lhs (rhs, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (toFrom rhs)
+     let ret = leftVal :& rightVal
+     pure $ (ret, fromJoin " INNER JOIN " leftFrom rightFrom (Just $ on' ret))
+
+
+-- | INNER JOIN LATERAL
+--
+-- A Lateral subquery join allows the joined query to reference entities from the
+-- left hand side of the join. Discards rows that don't match the on clause
+--
+-- Used as an infix operator \`innerJoinLateral\`
+--
+-- See example 6
+--
+-- @since 3.5.0.0
+innerJoinLateral :: ( ToFrom a a'
+                    , HasOnClause rhs (a' :& b)
+                    , SqlSelect b r
+                    , ToAlias b
+                    , ToAliasReference b
+                    , rhs ~ (a' -> SqlQuery b, (a' :& b) -> SqlExpr (Value Bool))
+                    )
+                 => a -> rhs -> From (a' :& b)
+innerJoinLateral lhs (rhsFn, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (selectQuery (rhsFn leftVal))
+     let ret = leftVal :& rightVal
+     pure $ (ret, fromJoin " INNER JOIN LATERAL " leftFrom rightFrom (Just $ on' ret))
+
+-- | CROSS JOIN
+--
+-- Used as an infix \`crossJoin\`
+--
+-- @
+-- select $ do
+-- from $ table \@Person
+-- \`crossJoin\` table \@BlogPost
+-- @
+--
+-- @since 3.5.0.0
+crossJoin :: ( ToFrom a a'
+             , ToFrom b b'
+             ) => a -> b -> From (a' :& b')
+crossJoin lhs rhs = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (toFrom rhs)
+     let ret = leftVal :& rightVal
+     pure $ (ret, fromJoin " CROSS JOIN " leftFrom rightFrom Nothing)
+
+-- | CROSS JOIN LATERAL
+--
+-- A Lateral subquery join allows the joined query to reference entities from the
+-- left hand side of the join.
+--
+-- Used as an infix operator \`crossJoinLateral\`
+--
+-- See example 6
+--
+-- @since 3.5.0.0
+crossJoinLateral :: ( ToFrom a a'
+                    , SqlSelect b r
+                    , ToAlias b
+                    , ToAliasReference b
+                    )
+                 => a -> (a' -> SqlQuery b) -> From (a' :& b)
+crossJoinLateral lhs rhsFn = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (selectQuery (rhsFn leftVal))
+     let ret = leftVal :& rightVal
+     pure $ (ret, fromJoin " CROSS JOIN LATERAL " leftFrom rightFrom Nothing)
+
+-- | LEFT OUTER JOIN
+--
+-- Join where the right side may not exist.
+-- If the on clause fails then the right side will be NULL'ed
+-- Because of this the right side needs to be handled as a Maybe
+--
+-- Used as an infix operator \`leftJoin\`
+--
+-- @
+-- select $
+-- from $ table \@Person
+-- \`leftJoin\` table \@BlogPost
+-- \`on\` (\\(p :& bp) ->
+--         p ^. PersonId ==. bp ?. BlogPostAuthorId)
+-- @
+--
+-- @since 3.5.0.0
+leftJoin :: ( ToFrom a a'
+            , ToFrom b b'
+            , ToMaybe b'
+            , HasOnClause rhs (a' :& ToMaybeT b')
+            , rhs ~ (b, (a' :& ToMaybeT b') -> SqlExpr (Value Bool))
+            ) => a -> rhs -> From (a' :& ToMaybeT b')
+leftJoin lhs (rhs, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (toFrom rhs)
+     let ret = leftVal :& toMaybe rightVal
+     pure $ (ret, fromJoin " LEFT OUTER JOIN " leftFrom rightFrom (Just $ on' ret))
+
+-- | LEFT OUTER JOIN LATERAL
+--
+-- Lateral join where the right side may not exist.
+-- In the case that the query returns nothing or the on clause fails the right
+-- side of the join will be NULL'ed
+-- Because of this the right side needs to be handled as a Maybe
+--
+-- Used as an infix operator \`leftJoinLateral\`
+--
+-- See example 6 for how to use LATERAL
+--
+-- @since 3.5.0.0
+leftJoinLateral :: ( ToFrom a a'
+                   , SqlSelect b r
+                   , HasOnClause rhs (a' :& ToMaybeT b)
+                   , ToAlias b
+                   , ToAliasReference b
+                   , ToMaybe b
+                   , rhs ~ (a' -> SqlQuery b, (a' :& ToMaybeT b) -> SqlExpr (Value Bool))
+                   )
+                 => a -> rhs -> From (a' :& ToMaybeT b)
+leftJoinLateral lhs (rhsFn, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (selectQuery (rhsFn leftVal))
+     let ret = leftVal :& toMaybe rightVal
+     pure $ (ret, fromJoin " LEFT OUTER JOIN LATERAL " leftFrom rightFrom (Just $ on' ret))
+
+-- | RIGHT OUTER JOIN
+--
+-- Join where the left side may not exist.
+-- If the on clause fails then the left side will be NULL'ed
+-- Because of this the left side needs to be handled as a Maybe
+--
+-- Used as an infix operator \`rightJoin\`
+--
+-- @
+-- select $
+-- from $ table \@Person
+-- \`rightJoin\` table \@BlogPost
+-- \`on\` (\\(p :& bp) ->
+--         p ?. PersonId ==. bp ^. BlogPostAuthorId)
+-- @
+--
+-- @since 3.5.0.0
+rightJoin :: ( ToFrom a a'
+             , ToFrom b b'
+             , ToMaybe a'
+             , HasOnClause rhs (ToMaybeT a' :& b')
+             , rhs ~ (b, (ToMaybeT a' :& b') -> SqlExpr (Value Bool))
+             ) => a -> rhs -> From (ToMaybeT a' :& b')
+rightJoin lhs (rhs, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (toFrom rhs)
+     let ret = toMaybe leftVal :& rightVal
+     pure $ (ret, fromJoin " RIGHT OUTER JOIN " leftFrom rightFrom (Just $ on' ret))
+
+-- | FULL OUTER JOIN
+--
+-- Join where both sides of the join may not exist.
+-- Because of this the result needs to be handled as a Maybe
+--
+-- Used as an infix operator \`fullOuterJoin\`
+--
+-- @
+-- select $
+-- from $ table \@Person
+-- \`fullOuterJoin\` table \@BlogPost
+-- \`on\` (\\(p :& bp) ->
+--         p ?. PersonId ==. bp ?. BlogPostAuthorId)
+-- @
+--
+-- @since 3.5.0.0
+fullOuterJoin :: ( ToFrom a a'
+                 , ToFrom b b'
+                 , ToMaybe a'
+                 , ToMaybe b'
+                 , HasOnClause rhs (ToMaybeT a' :& ToMaybeT b')
+                 , rhs ~ (b, (ToMaybeT a' :& ToMaybeT b') -> SqlExpr (Value Bool))
+                 ) => a -> rhs -> From (ToMaybeT a' :& ToMaybeT b')
+fullOuterJoin lhs (rhs, on') = From $ do
+     (leftVal, leftFrom) <- unFrom (toFrom lhs)
+     (rightVal, rightFrom) <- unFrom (toFrom rhs)
+     let ret = toMaybe leftVal :& toMaybe rightVal
+     pure $ (ret, fromJoin " FULL OUTER JOIN " leftFrom rightFrom (Just $ on' ret))
+
+infixl 2 `innerJoin`,
+         `innerJoinLateral`,
+         `leftJoin`,
+         `leftJoinLateral`,
+         `crossJoin`,
+         `crossJoinLateral`,
+         `rightJoin`,
+         `fullOuterJoin`
+
+
+------ Compatibility for old syntax
+
+data Lateral
+data NotLateral
+
+type family IsLateral a where
+    IsLateral (a -> SqlQuery b, c) = Lateral
+    IsLateral (a -> SqlQuery b) = Lateral
+    IsLateral a = NotLateral
+
+class DoInnerJoin lateral lhs rhs res | lateral rhs lhs -> res where
+    doInnerJoin :: Proxy lateral -> lhs -> rhs -> From res
+
+instance ( ToFrom a a'
+         , ToFrom b b'
+         , HasOnClause rhs (a' :& b')
+         , rhs ~ (b, (a' :& b') -> SqlExpr (Value Bool))
+         ) => DoInnerJoin NotLateral a rhs (a' :& b') where
+    doInnerJoin _ = innerJoin
+
+instance ( ToFrom a a'
+         , SqlSelect b r
+         , ToAlias b
+         , ToAliasReference b
+         , d ~ (a' :& b)
+         ) => DoInnerJoin Lateral a (a' -> SqlQuery b, d -> SqlExpr (Value Bool)) d where
+    doInnerJoin _ = innerJoinLateral
+
+instance ( DoInnerJoin lateral lhs rhs r, lateral ~ IsLateral rhs )
+           => ToFrom (InnerJoin lhs rhs) r where
+     toFrom (InnerJoin a b) = doInnerJoin (Proxy @lateral) a b
+
+class DoLeftJoin lateral lhs rhs res | lateral rhs lhs -> res where
+    doLeftJoin :: Proxy lateral -> lhs -> rhs -> From res
+
+instance ( ToFrom a a'
+         , ToFrom b b'
+         , ToMaybe b'
+         , ToMaybeT b' ~ mb
+         , HasOnClause rhs (a' :& mb)
+         , rhs ~ (b, (a' :& mb) -> SqlExpr (Value Bool))
+         ) => DoLeftJoin NotLateral a rhs (a' :& mb) where
+    doLeftJoin _ = leftJoin
+
+instance ( ToFrom a a'
+         , ToMaybe b
+         , d ~ (a' :& ToMaybeT b)
+         , SqlSelect b r
+         , ToAlias b
+         , ToAliasReference b
+         ) => DoLeftJoin Lateral a (a' -> SqlQuery b, d -> SqlExpr (Value Bool)) d where
+    doLeftJoin _ = leftJoinLateral
+
+instance ( DoLeftJoin lateral lhs rhs r, lateral ~ IsLateral rhs )
+           => ToFrom (LeftOuterJoin lhs rhs) r where
+     toFrom (LeftOuterJoin a b) = doLeftJoin (Proxy @lateral) a b
+
+class DoCrossJoin lateral lhs rhs res | lateral lhs rhs -> res where
+    doCrossJoin :: Proxy lateral -> lhs -> rhs -> From res
+
+instance (ToFrom a a', ToFrom b b') => DoCrossJoin NotLateral a b (a' :& b') where
+    doCrossJoin _ = crossJoin
+instance (ToFrom a a', SqlSelect b r, ToAlias b, ToAliasReference b)
+  => DoCrossJoin Lateral a (a' -> SqlQuery b) (a' :& b) where
+    doCrossJoin _ = crossJoinLateral
+
+instance (DoCrossJoin lateral lhs rhs r, IsLateral rhs ~ lateral)
+  => ToFrom (CrossJoin lhs rhs) r where
+    toFrom (CrossJoin a b) = doCrossJoin (Proxy @lateral) a b
+
+instance ( ToFrom a a'
+         , ToFrom b b'
+         , ToMaybe a'
+         , ToMaybeT a' ~ ma
+         , HasOnClause rhs (ma :& b')
+         , ErrorOnLateral b
+         , rhs ~ (b, (ma :& b') -> SqlExpr (Value Bool))
+         ) => ToFrom (RightOuterJoin a rhs) (ma :& b') where
+    toFrom (RightOuterJoin a b) = rightJoin a b
+
+instance ( ToFrom a a'
+         , ToFrom b b'
+         , ToMaybe a'
+         , ToMaybeT a' ~ ma
+         , ToMaybe b'
+         , ToMaybeT b' ~ mb
+         , HasOnClause rhs (ma :& mb)
+         , ErrorOnLateral b
+         , rhs ~ (b, (ma :& mb) -> SqlExpr (Value Bool))
+         ) => ToFrom (FullOuterJoin a rhs) (ma :& mb) where
+    toFrom (FullOuterJoin a b) = fullOuterJoin a b
+

src/Database/Esqueleto/Experimental/From/SqlSetOperation.hs

@@ -0,0 +1,130 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Database.Esqueleto.Experimental.From.SqlSetOperation
+        where
+
+import Control.Arrow (first)
+import Control.Monad.Trans.Class (lift)
+import qualified Control.Monad.Trans.State as S
+import qualified Control.Monad.Trans.Writer as W
+import qualified Data.Text.Lazy.Builder as TLB
+import Database.Esqueleto.Experimental.From
+import Database.Esqueleto.Experimental.ToAlias
+import Database.Esqueleto.Experimental.ToAliasReference
+import Database.Esqueleto.Internal.Internal hiding (From(..), from, on)
+import Database.Esqueleto.Internal.PersistentImport (PersistValue)
+
+-- | Data type used to implement the SqlSetOperation language
+-- this type is implemented in the same way as a @From@
+--
+-- Semantically a @SqlSetOperation@ is always a @From@ but not vice versa
+--
+-- @since 3.5.0.0
+newtype SqlSetOperation a = SqlSetOperation
+    { unSqlSetOperation :: NeedParens -> SqlQuery (a, IdentInfo -> (TLB.Builder, [PersistValue]))}
+
+instance ToAliasReference a => ToFrom (SqlSetOperation a) a where
+    toFrom setOperation = From $ do
+        ident <- newIdentFor (DBName "u")
+        (a, fromClause) <- unSqlSetOperation setOperation Never
+        ref <- toAliasReference ident a
+        pure (ref, \_ info -> (first parens $ fromClause info) <> (" AS " <> useIdent info ident, mempty))
+
+-- | Type class to support direct use of @SqlQuery@ in a set operation tree
+--
+-- @since 3.5.0.0
+class ToSqlSetOperation a r | a -> r where
+    toSqlSetOperation :: a -> SqlSetOperation r
+instance ToSqlSetOperation (SqlSetOperation a) a where
+    toSqlSetOperation = id
+instance (SqlSelect a r, ToAlias a, ToAliasReference a) => ToSqlSetOperation (SqlQuery a) a where
+    toSqlSetOperation subquery =
+        SqlSetOperation $ \p -> do
+            (ret, sideData) <- Q $ W.censor (\_ -> mempty) $ W.listen $ unQ subquery
+            state <- Q $ lift S.get
+            aliasedValue <- toAlias ret
+            Q $ lift $ S.put state
+            let aliasedQuery = Q $ W.WriterT $ pure (aliasedValue, sideData)
+            let p' =
+                  case p of
+                    Parens -> Parens
+                    Never ->
+                      if (sdLimitClause sideData) /= mempty
+                          || length (sdOrderByClause sideData) > 0 then
+                        Parens
+                      else
+                        Never
+            pure (aliasedValue, \info -> first (parensM p') $ toRawSql SELECT info aliasedQuery)
+
+-- | Helper function for defining set operations
+-- @since 3.5.0.0
+mkSetOperation :: (ToSqlSetOperation a a', ToSqlSetOperation b a')
+               => TLB.Builder -> a -> b -> SqlSetOperation a'
+mkSetOperation operation lhs rhs = SqlSetOperation $ \p -> do
+    (leftValue, leftClause) <- unSqlSetOperation (toSqlSetOperation lhs) p
+    (_, rightClause) <- unSqlSetOperation (toSqlSetOperation rhs) p
+    pure (leftValue, \info -> leftClause info <> (operation, mempty) <> rightClause info)
+
+{-# DEPRECATED Union "/Since: 3.4.0.0/ - Use the 'union_' function instead of the 'Union' data constructor" #-}
+data Union a b = a `Union` b
+instance ToSqlSetOperation a a' => ToSqlSetOperation (Union a a) a' where
+    toSqlSetOperation (Union a b) = union_ a b
+
+-- | Overloaded @union_@ function to support use in both 'SqlSetOperation'
+-- and 'withRecursive'
+--
+-- @since 3.5.0.0
+class Union_ a where
+    -- | @UNION@ SQL set operation. Can be used as an infix function between 'SqlQuery' values.
+    union_ :: a
+
+instance (ToSqlSetOperation a c, ToSqlSetOperation b c, res ~ SqlSetOperation c)
+  => Union_ (a -> b -> res) where
+    union_ = mkSetOperation " UNION "
+
+-- | Overloaded @unionAll_@ function to support use in both 'SqlSetOperation'
+-- and 'withRecursive'
+--
+-- @since 3.5.0.0
+class UnionAll_ a where
+    -- | @UNION@ @ALL@ SQL set operation. Can be used as an infix function between 'SqlQuery' values.
+    unionAll_ :: a
+instance (ToSqlSetOperation a c, ToSqlSetOperation b c, res ~ SqlSetOperation c)
+  => UnionAll_ (a -> b -> res) where
+    unionAll_ = mkSetOperation " UNION ALL "
+
+{-# DEPRECATED UnionAll "/Since: 3.4.0.0/ - Use the 'unionAll_' function instead of the 'UnionAll' data constructor" #-}
+data UnionAll a b = a `UnionAll` b
+instance ToSqlSetOperation a a' => ToSqlSetOperation (UnionAll a a) a' where
+    toSqlSetOperation (UnionAll a b) = unionAll_ a b
+
+{-# DEPRECATED Except "/Since: 3.4.0.0/ - Use the 'except_' function instead of the 'Except' data constructor" #-}
+data Except a b = a `Except` b
+instance ToSqlSetOperation a a' => ToSqlSetOperation (Except a a) a' where
+    toSqlSetOperation (Except a b) = except_ a b
+
+-- | @EXCEPT@ SQL set operation. Can be used as an infix function between 'SqlQuery' values.
+except_ :: (ToSqlSetOperation a a', ToSqlSetOperation b a') => a -> b -> SqlSetOperation a'
+except_ = mkSetOperation " EXCEPT "
+
+{-# DEPRECATED Intersect "/Since: 3.4.0.0/ - Use the 'intersect_' function instead of the 'Intersect' data constructor" #-}
+data Intersect a b = a `Intersect` b
+instance ToSqlSetOperation a a' => ToSqlSetOperation (Intersect a a) a' where
+    toSqlSetOperation (Intersect a b) = intersect_ a b
+
+-- | @INTERSECT@ SQL set operation. Can be used as an infix function between 'SqlQuery' values.
+intersect_ :: (ToSqlSetOperation a a', ToSqlSetOperation b a') => a -> b -> SqlSetOperation a'
+intersect_ = mkSetOperation " INTERSECT "
+
+{-# DEPRECATED SelectQuery "/Since: 3.4.0.0/ - It is no longer necessary to tag 'SqlQuery' values with @SelectQuery@" #-}
+pattern SelectQuery a = a
+

src/Database/Esqueleto/Experimental/ToAlias.hs

@@ -0,0 +1,92 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module Database.Esqueleto.Experimental.ToAlias
+    where
+
+import Database.Esqueleto.Internal.Internal hiding (From, from, on)
+import Database.Esqueleto.Internal.PersistentImport
+
+{-# DEPRECATED ToAliasT "This type alias doesn't do anything. Please delete it. Will be removed in the next release." #-}
+type ToAliasT a = a
+
+-- Tedious tuple magic
+class ToAlias a where
+    toAlias :: a -> SqlQuery a
+
+instance ToAlias (SqlExpr (Value a)) where
+    toAlias e@(ERaw m f)
+      | Just _ <- sqlExprMetaAlias m = pure e
+      | otherwise = do
+            ident <- newIdentFor (DBName "v")
+            pure $ ERaw noMeta{sqlExprMetaAlias = Just ident} f
+
+instance ToAlias (SqlExpr (Entity a)) where
+    toAlias e@(ERaw m f)
+      | Just _ <- sqlExprMetaAlias m = pure e
+      | otherwise = do
+           ident <- newIdentFor (DBName "v")
+           pure $ ERaw m{sqlExprMetaIsReference = False, sqlExprMetaAlias = Just ident} f
+
+instance ToAlias (SqlExpr (Maybe (Entity a))) where
+    -- FIXME: Code duplication because the compiler doesnt like half final encoding
+    toAlias e@(ERaw m f)
+      | Just _ <- sqlExprMetaAlias m = pure e
+      | otherwise = do
+           ident <- newIdentFor (DBName "v")
+           pure $ ERaw m{sqlExprMetaIsReference = False, sqlExprMetaAlias = Just ident} f
+
+instance (ToAlias a, ToAlias b) => ToAlias (a,b) where
+    toAlias (a,b) = (,) <$> toAlias a <*> toAlias b
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         ) => ToAlias (a,b,c) where
+    toAlias x = to3 <$> (toAlias $ from3 x)
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         , ToAlias d
+         ) => ToAlias (a,b,c,d) where
+    toAlias x = to4 <$> (toAlias $ from4 x)
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         , ToAlias d
+         , ToAlias e
+         ) => ToAlias (a,b,c,d,e) where
+    toAlias x = to5 <$> (toAlias $ from5 x)
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         , ToAlias d
+         , ToAlias e
+         , ToAlias f
+         ) => ToAlias (a,b,c,d,e,f) where
+    toAlias x = to6 <$> (toAlias $ from6 x)
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         , ToAlias d
+         , ToAlias e
+         , ToAlias f
+         , ToAlias g
+         ) => ToAlias (a,b,c,d,e,f,g) where
+    toAlias x = to7 <$> (toAlias $ from7 x)
+
+instance ( ToAlias a
+         , ToAlias b
+         , ToAlias c
+         , ToAlias d
+         , ToAlias e
+         , ToAlias f
+         , ToAlias g
+         , ToAlias h
+         ) => ToAlias (a,b,c,d,e,f,g,h) where
+    toAlias x = to8 <$> (toAlias $ from8 x)

src/Database/Esqueleto/Experimental/ToAliasReference.hs

@@ -0,0 +1,90 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module Database.Esqueleto.Experimental.ToAliasReference
+    where
+
+import Data.Coerce
+import Database.Esqueleto.Internal.Internal hiding (From, from, on)
+import Database.Esqueleto.Internal.PersistentImport
+
+{-# DEPRECATED ToAliasReferenceT "This type alias doesn't do anything. Please delete it. Will be removed in the next release." #-}
+type ToAliasReferenceT a = a
+
+-- more tedious tuple magic
+class ToAliasReference a where
+    toAliasReference :: Ident -> a -> SqlQuery a
+
+instance ToAliasReference (SqlExpr (Value a)) where
+    toAliasReference aliasSource (ERaw m _)
+      | Just alias <- sqlExprMetaAlias m = pure $ ERaw m{sqlExprMetaIsReference = True} $ \_ info ->
+          (useIdent info aliasSource <> "." <> useIdent info alias, [])
+    toAliasReference _ e = pure e
+
+instance ToAliasReference (SqlExpr (Entity a)) where
+    toAliasReference aliasSource (ERaw m _)
+      | Just _ <- sqlExprMetaAlias m =
+          pure $ ERaw m{sqlExprMetaIsReference = True} $ \_ info ->
+            (useIdent info aliasSource, [])
+    toAliasReference _ e = pure e
+
+instance ToAliasReference (SqlExpr (Maybe (Entity a))) where
+    toAliasReference aliasSource e =
+        coerce <$> toAliasReference aliasSource (coerce e :: SqlExpr (Entity a))
+
+
+instance (ToAliasReference a, ToAliasReference b) => ToAliasReference (a, b) where
+    toAliasReference ident (a,b) = (,) <$> (toAliasReference ident a) <*> (toAliasReference ident b)
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         ) => ToAliasReference (a,b,c) where
+    toAliasReference ident x = fmap to3 $ toAliasReference ident $ from3 x
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         , ToAliasReference d
+         ) => ToAliasReference (a,b,c,d) where
+    toAliasReference ident x = fmap to4 $ toAliasReference ident $ from4 x
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         , ToAliasReference d
+         , ToAliasReference e
+         ) => ToAliasReference (a,b,c,d,e) where
+    toAliasReference ident x = fmap to5 $ toAliasReference ident $ from5 x
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         , ToAliasReference d
+         , ToAliasReference e
+         , ToAliasReference f
+         ) => ToAliasReference (a,b,c,d,e,f) where
+    toAliasReference ident x = to6 <$> (toAliasReference ident $ from6 x)
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         , ToAliasReference d
+         , ToAliasReference e
+         , ToAliasReference f
+         , ToAliasReference g
+         ) => ToAliasReference (a,b,c,d,e,f,g) where
+    toAliasReference ident x = to7 <$> (toAliasReference ident $ from7 x)
+
+instance ( ToAliasReference a
+         , ToAliasReference b
+         , ToAliasReference c
+         , ToAliasReference d
+         , ToAliasReference e
+         , ToAliasReference f
+         , ToAliasReference g
+         , ToAliasReference h
+         ) => ToAliasReference (a,b,c,d,e,f,g,h) where
+    toAliasReference ident x = to8 <$> (toAliasReference ident $ from8 x)
+

src/Database/Esqueleto/Experimental/ToMaybe.hs

@@ -0,0 +1,79 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module Database.Esqueleto.Experimental.ToMaybe
+    where
+
+import Database.Esqueleto.Internal.Internal hiding (From(..), from, on)
+import Database.Esqueleto.Internal.PersistentImport (Entity(..))
+
+type family Nullable a where
+    Nullable (Maybe a) = a
+    Nullable a =  a
+
+class ToMaybe a where
+    type ToMaybeT a
+    toMaybe :: a -> ToMaybeT a
+
+instance ToMaybe (SqlExpr (Maybe a)) where
+    type ToMaybeT (SqlExpr (Maybe a)) = SqlExpr (Maybe a)
+    toMaybe = id
+
+instance ToMaybe (SqlExpr (Entity a)) where
+    type ToMaybeT (SqlExpr (Entity a)) = SqlExpr (Maybe (Entity a))
+    toMaybe (ERaw f m) = (ERaw f m)
+
+instance ToMaybe (SqlExpr (Value a)) where
+    type ToMaybeT (SqlExpr (Value a)) = SqlExpr (Value (Maybe (Nullable a)))
+    toMaybe = veryUnsafeCoerceSqlExprValue
+
+
+instance (ToMaybe a, ToMaybe b) => ToMaybe (a,b) where
+    type ToMaybeT (a, b) = (ToMaybeT a, ToMaybeT b)
+    toMaybe (a, b) = (toMaybe a, toMaybe b)
+
+instance ( ToMaybe a , ToMaybe b , ToMaybe c) => ToMaybe (a,b,c) where
+    type ToMaybeT (a, b, c) = (ToMaybeT a, ToMaybeT b, ToMaybeT c)
+    toMaybe = to3 . toMaybe . from3
+
+instance ( ToMaybe a , ToMaybe b , ToMaybe c , ToMaybe d) => ToMaybe (a,b,c,d) where
+    type ToMaybeT (a, b, c, d) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d)
+    toMaybe = to4 . toMaybe . from4
+
+instance ( ToMaybe a , ToMaybe b , ToMaybe c , ToMaybe d , ToMaybe e) => ToMaybe (a,b,c,d,e) where
+    type ToMaybeT (a, b, c, d, e) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e)
+    toMaybe = to5 . toMaybe . from5
+
+instance ( ToMaybe a
+         , ToMaybe b
+         , ToMaybe c
+         , ToMaybe d
+         , ToMaybe e
+         , ToMaybe f
+         ) => ToMaybe (a,b,c,d,e,f) where
+    type ToMaybeT (a, b, c, d, e, f) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f)
+    toMaybe = to6 . toMaybe . from6
+
+instance ( ToMaybe a
+         , ToMaybe b
+         , ToMaybe c
+         , ToMaybe d
+         , ToMaybe e
+         , ToMaybe f
+         , ToMaybe g
+         ) => ToMaybe (a,b,c,d,e,f,g) where
+    type ToMaybeT (a, b, c, d, e, f, g) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f, ToMaybeT g)
+    toMaybe = to7 . toMaybe . from7
+
+instance ( ToMaybe a
+         , ToMaybe b
+         , ToMaybe c
+         , ToMaybe d
+         , ToMaybe e
+         , ToMaybe f
+         , ToMaybe g
+         , ToMaybe h
+         ) => ToMaybe (a,b,c,d,e,f,g,h) where
+     type ToMaybeT (a, b, c, d, e, f, g, h) = (ToMaybeT a, ToMaybeT b, ToMaybeT c, ToMaybeT d, ToMaybeT e, ToMaybeT f, ToMaybeT g, ToMaybeT h)
+     toMaybe = to8 . toMaybe . from8
+

src/Database/Esqueleto/Internal/ExprParser.hs

@@ -1,21 +1,22 @@
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RecordWildCards   #-}
+{-# LANGUAGE RecordWildCards #-}
 
 -- | This is an internal module. This module may have breaking changes without
 -- a corresponding major version bump. If you use this module, please open an
 -- issue with your use-case so we can safely support it.
 module Database.Esqueleto.Internal.ExprParser where
 
-import           Prelude              hiding (takeWhile)
+import Prelude hiding (takeWhile)
 
-import           Control.Applicative  ((<|>))
-import           Control.Monad        (void)
-import           Data.Attoparsec.Text
-import           Data.Set             (Set)
-import qualified Data.Set             as Set
-import           Data.Text            (Text)
-import qualified Data.Text            as Text
-import           Database.Persist.Sql
+import Control.Applicative ((<|>))
+import Control.Monad (void)
+import Data.Attoparsec.Text
+import Data.Set (Set)
+import qualified Data.Set as Set
+import Data.Text (Text)
+import qualified Data.Text as Text
+import Database.Persist.Sql
+import Database.Persist.SqlBackend
 
 -- | A type representing the access of a table value. In Esqueleto, we get
 -- a guarantee that the access will look something like:
@@ -26,54 +27,54 @@ import           Database.Persist.Sql
 --             table name                            column name
 -- @
 data TableAccess = TableAccess
-  { tableAccessTable  :: Text
-  , tableAccessColumn :: Text
-  }
-  deriving (Eq, Ord, Show)
+    { tableAccessTable  :: Text
+    , tableAccessColumn :: Text
+    }
+    deriving (Eq, Ord, Show)
 
 -- | Parse a @SqlExpr (Value Bool)@'s textual representation into a list of
 -- 'TableAccess'
 parseOnExpr :: SqlBackend -> Text -> Either String (Set TableAccess)
 parseOnExpr sqlBackend text = do
-  c <- mkEscapeChar sqlBackend
-  parseOnly (onExpr c) text
+    c <- mkEscapeChar sqlBackend
+    parseOnly (onExpr c) text
 
 -- | This function uses the 'connEscapeName' function in the 'SqlBackend' with an
 -- empty identifier to pull out an escape character. This implementation works
 -- with postgresql, mysql, and sqlite backends.
 mkEscapeChar :: SqlBackend -> Either String Char
 mkEscapeChar sqlBackend =
-  case Text.uncons (connEscapeName sqlBackend (DBName "")) of
-    Nothing ->
-      Left "Failed to get an escape character from the SQL backend."
-    Just (c, _) ->
-      Right c
+    case Text.uncons (getEscapedRawName "" sqlBackend) of
+        Nothing ->
+            Left "Failed to get an escape character from the SQL backend."
+        Just (c, _) ->
+            Right c
 
 type ExprParser a = Char -> Parser a
 
 onExpr :: ExprParser (Set TableAccess)
 onExpr e = Set.fromList <$> many' tableAccesses
   where
-   tableAccesses = do
-     skipToEscape e <?> "Skipping to an escape char"
-     parseTableAccess e <?> "Parsing a table access"
+    tableAccesses = do
+        skipToEscape e <?> "Skipping to an escape char"
+        parseTableAccess e <?> "Parsing a table access"
 
 skipToEscape :: ExprParser ()
 skipToEscape escapeChar = void (takeWhile (/= escapeChar))
 
 parseEscapedIdentifier :: ExprParser [Char]
 parseEscapedIdentifier escapeChar = do
-  char escapeChar
-  str <- parseEscapedChars escapeChar
-  char escapeChar
-  pure str
+    _ <- char escapeChar
+    str <- parseEscapedChars escapeChar
+    _ <- char escapeChar
+    pure str
 
 parseTableAccess :: ExprParser TableAccess
 parseTableAccess ec = do
-  tableAccessTable <- Text.pack <$> parseEscapedIdentifier ec
-  _ <- char '.'
-  tableAccessColumn <- Text.pack <$> parseEscapedIdentifier ec
-  pure TableAccess {..}
+    tableAccessTable <- Text.pack <$> parseEscapedIdentifier ec
+    _ <- char '.'
+    tableAccessColumn <- Text.pack <$> parseEscapedIdentifier ec
+    pure TableAccess {..}
 
 parseEscapedChars :: ExprParser [Char]
 parseEscapedChars escapeChar = go

src/Database/Esqueleto/Internal/Language.hs

@@ -1,69 +0,0 @@
-{-# LANGUAGE DeriveDataTypeable
-           , EmptyDataDecls
-           , FlexibleContexts
-           , FlexibleInstances
-           , FunctionalDependencies
-           , MultiParamTypeClasses
-           , TypeFamilies
-           , UndecidableInstances
-           , GADTs
- #-}
--- | This is an internal module, anything exported by this module
--- may change without a major version bump.  Please use only
--- "Database.Esqueleto" if possible.
-module Database.Esqueleto.Internal.Language
-  ( -- * The pretty face
-    from
-  , Value(..)
-  , ValueList(..)
-  , SomeValue(..)
-  , ToSomeValues(..)
-  , InnerJoin(..)
-  , CrossJoin(..)
-  , LeftOuterJoin(..)
-  , RightOuterJoin(..)
-  , FullOuterJoin(..)
-  , OnClauseWithoutMatchingJoinException(..)
-  , OrderBy
-  , DistinctOn
-  , Update
-  , Insertion
-  , LockingKind(..)
-  , SqlString
-  , ToBaseId(..)
-    -- * The guts
-  , JoinKind(..)
-  , IsJoinKind(..)
-  , BackendCompatible(..)
-  , PreprocessedFrom
-  , From
-  , FromPreprocess
-  , when_
-  , then_
-  , else_
-  , where_, on, groupBy, orderBy, rand, asc, desc, limit, offset
-             , distinct, distinctOn, don, distinctOnOrderBy, having, locking
-             , sub_select, (^.), (?.)
-             , val, isNothing, just, nothing, joinV, withNonNull
-             , countRows, count, countDistinct
-             , not_, (==.), (>=.), (>.), (<=.), (<.), (!=.), (&&.), (||.)
-             , between, (+.), (-.), (/.), (*.)
-             , random_, round_, ceiling_, floor_
-             , min_, max_, sum_, avg_, castNum, castNumM
-             , coalesce, coalesceDefault
-             , lower_, upper_, trim_, ltrim_, rtrim_, length_, left_, right_
-             , like, ilike, (%), concat_, (++.), castString
-             , subList_select, valList, justList
-             , in_, notIn, exists, notExists
-             , set, (=.), (+=.), (-=.), (*=.), (/=.)
-             , case_, toBaseId, (<#), (<&>)
-  , subSelect
-  , subSelectMaybe
-  , subSelectCount
-  , subSelectList
-  , subSelectForeign
-  , subSelectUnsafe
-  ) where
-
-import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Internal

src/Database/Esqueleto/Internal/PersistentImport.hs

@@ -3,148 +3,175 @@
 module Database.Esqueleto.Internal.PersistentImport
 -- NOTE: switch back to a module export once https://gitlab.haskell.org/ghc/ghc/merge_requests/276
 -- has been merged. See https://github.com/bitemyapp/esqueleto/issues/110 for more details
-  ( toJsonText,
-  entityIdFromJSON,
-  entityIdToJSON,
-  entityValues,
-  fromPersistValueJSON,
-  keyValueEntityFromJSON,
-  keyValueEntityToJSON,
-  toPersistValueJSON,
-  selectKeys,
-  belongsTo,
-  belongsToJust,
-  getEntity,
-  getJust,
-  getJustEntity,
-  insertEntity,
-  insertRecord,
-  liftPersist,
-  checkUnique,
-  getByValue,
-  insertBy,
-  insertUniqueEntity,
-  onlyUnique,
-  replaceUnique,
-  transactionSave,
-  transactionUndo,
-  defaultAttribute,
-  mkColumns,
-  getMigration,
-  migrate,
-  parseMigration,
-  parseMigration',
-  printMigration,
-  runMigration,
-  runMigrationSilent,
-  runMigrationUnsafe,
-  showMigration,
-  decorateSQLWithLimitOffset,
-  fieldDBName,
-  fromSqlKey,
-  getFieldName,
-  getTableName,
-  tableDBName,
-  toSqlKey,
-  withRawQuery,
-  getStmtConn,
-  rawExecute,
-  rawExecuteCount,
-  rawQuery,
-  rawQueryRes,
-  rawSql,
-  askLogFunc,
-  close',
-  createSqlPool,
-  liftSqlPersistMPool,
-  runSqlConn,
-  runSqlPersistM,
-  runSqlPersistMPool,
-  runSqlPool,
-  withSqlConn,
-  withSqlPool,
-  readToUnknown,
-  readToWrite,
-  writeToUnknown,
-  entityKeyFields,
-  entityPrimary,
-  fromPersistValueText,
-  keyAndEntityFields,
-  toEmbedEntityDef,
-  PersistStore,
-  PersistUnique,
-  DeleteCascade(..),
-  PersistConfig(..),
-  BackendSpecificUpdate,
-  Entity(..),
-  PersistEntity(..),
-  PersistField(..),
-  SomePersistField(..),
-  PersistQueryRead(..),
-  PersistQueryWrite(..),
-  BackendCompatible(..),
-  BackendKey(..),
-  HasPersistBackend(..),
-  IsPersistBackend,
-  PersistCore(..),
-  PersistRecordBackend,
-  PersistStoreRead(..),
-  PersistStoreWrite(..),
-  ToBackendKey(..),
-  PersistUniqueRead(..),
-  PersistUniqueWrite(..),
-  PersistFieldSql(..),
-  RawSql(..),
-  CautiousMigration,
-  Column(..),
-  ConnectionPool,
-  Migration,
-  PersistentSqlException(..),
-  Single(..),
-  Sql,
-  SqlPersistM,
-  SqlPersistT,
-  InsertSqlResult(..),
-  IsSqlBackend,
-  LogFunc,
-  SqlBackend(..),
-  SqlBackendCanRead,
-  SqlBackendCanWrite,
-  SqlReadBackend(..),
-  SqlReadT,
-  SqlWriteBackend(..),
-  SqlWriteT,
-  Statement(..),
-  Attr,
-  Checkmark(..),
-  CompositeDef(..),
-  DBName(..),
-  EmbedEntityDef(..),
-  EmbedFieldDef(..),
-  EntityDef(..),
-  ExtraLine,
-  FieldDef(..),
-  FieldType(..),
-  ForeignDef(..),
-  ForeignFieldDef,
-  HaskellName(..),
-  IsNullable(..),
-  OnlyUniqueException(..),
-  PersistException(..),
-  PersistFilter(..),
-  PersistUpdate(..),
-  PersistValue(..),
-  ReferenceDef(..),
-  SqlType(..),
-  UniqueDef(..),
-  UpdateException(..),
-  WhyNullable(..)
-  ) where
+    ( toJsonText
+    , entityIdFromJSON
+    , entityIdToJSON
+    , entityValues
+    , fromPersistValueJSON
+    , keyValueEntityFromJSON
+    , keyValueEntityToJSON
+    , toPersistValueJSON
+    , selectKeys
+    , belongsTo
+    , belongsToJust
+    , getEntity
+    , getJust
+    , getJustEntity
+    , insertEntity
+    , insertRecord
+    , liftPersist
+    , checkUnique
+    , getByValue
+    , insertBy
+    , insertUniqueEntity
+    , onlyUnique
+    , replaceUnique
+    , transactionSave
+    , transactionUndo
+    , defaultAttribute
+    , mkColumns
+    , getMigration
+    , migrate
+    , parseMigration
+    , parseMigration'
+    , printMigration
+    , runMigration
+    , runMigrationSilent
+    , runMigrationUnsafe
+    , showMigration
+    , decorateSQLWithLimitOffset
+    , fieldDBName
+    , fromSqlKey
+    , getFieldName
+    , getTableName
+    , tableDBName
+    , toSqlKey
+    , withRawQuery
+    , getStmtConn
+    , rawExecute
+    , rawExecuteCount
+    , rawQuery
+    , rawQueryRes
+    , rawSql
+    , close'
+    , createSqlPool
+    , liftSqlPersistMPool
+    , runSqlConn
+    , runSqlPersistM
+    , runSqlPersistMPool
+    , runSqlPool
+    , withSqlConn
+    , withSqlPool
+    , readToUnknown
+    , readToWrite
+    , writeToUnknown
+    , getEntityKeyFields
+    , entityPrimary
+    , keyAndEntityFields
+    , PersistStore
+    , PersistUnique
+    , DeleteCascade(..)
+    , PersistConfig(..)
+    , BackendSpecificUpdate
+    , Entity(..)
+    , PersistEntity(..)
+    , PersistField(..)
+    , SomePersistField(..)
+    , PersistQueryRead(..)
+    , PersistQueryWrite(..)
+    , BackendCompatible(..)
+    , BackendKey(..)
+    , HasPersistBackend(..)
+    , IsPersistBackend
+    , PersistCore(..)
+    , PersistRecordBackend
+    , PersistStoreRead(..)
+    , PersistStoreWrite(..)
+    , ToBackendKey(..)
+    , PersistUniqueRead(..)
+    , PersistUniqueWrite(..)
+    , PersistFieldSql(..)
+    , RawSql(..)
+    , CautiousMigration
+    , Column(..)
+    , ConnectionPool
+    , Migration
+    , PersistentSqlException(..)
+    , Single(..)
+    , Sql
+    , SqlPersistM
+    , SqlPersistT
+    , InsertSqlResult(..)
+    , IsSqlBackend
+    , LogFunc
+    , SqlBackend
+    , SqlBackendCanRead
+    , SqlBackendCanWrite
+    , SqlReadBackend(..)
+    , SqlReadT
+    , SqlWriteBackend(..)
+    , SqlWriteT
+    , Statement(..)
+    , Attr
+    , Checkmark(..)
+    , CompositeDef(..)
+    , EmbedEntityDef(..)
+    , EmbedFieldDef(..)
+    , EntityDef
+    , EntityIdDef(..)
+    , ExtraLine
+    , FieldDef(..)
+    , FieldType(..)
+    , ForeignDef(..)
+    , ForeignFieldDef
+    , IsNullable(..)
+    , PersistException(..)
+    , PersistFilter(..)
+    , PersistUpdate(..)
+    , PersistValue(..)
+    , ReferenceDef(..)
+    , SqlType(..)
+    , UniqueDef(..)
+    , UpdateException(..)
+    , WhyNullable(..)
+    , getEntityFields
+    , getEntityId
+    , getEntityDBName
+    , getEntityUniques
+    ) where
 
 import Database.Persist.Sql hiding
-  ( BackendSpecificFilter, Filter(..), PersistQuery, SelectOpt(..)
-  , Update(..), delete, deleteWhereCount, updateWhereCount, selectList
-  , selectKeysList, deleteCascadeWhere, (=.), (+=.), (-=.), (*=.), (/=.)
-  , (==.), (!=.), (<.), (>.), (<=.), (>=.), (<-.), (/<-.), (||.)
-  , listToJSON, mapToJSON, getPersistMap, limitOffsetOrder, selectSource
-  , update , count )
+       ( BackendSpecificFilter
+       , Filter(..)
+       , PersistQuery
+       , SelectOpt(..)
+       , Update(..)
+       , count
+       , delete
+       , deleteCascadeWhere
+       , deleteWhereCount
+       , exists
+       , getPersistMap
+       , limitOffsetOrder
+       , listToJSON
+       , mapToJSON
+       , selectKeysList
+       , selectList
+       , selectSource
+       , update
+       , updateWhereCount
+       , (!=.)
+       , (*=.)
+       , (+=.)
+       , (-=.)
+       , (/<-.)
+       , (/=.)
+       , (<-.)
+       , (<.)
+       , (<=.)
+       , (=.)
+       , (==.)
+       , (>.)
+       , (>=.)
+       , (||.)
+       )

src/Database/Esqueleto/Internal/Sql.hs

@@ -1,78 +0,0 @@
-{-# LANGUAGE DeriveDataTypeable
-           , EmptyDataDecls
-           , FlexibleContexts
-           , FlexibleInstances
-           , FunctionalDependencies
-           , MultiParamTypeClasses
-           , TypeFamilies
-           , UndecidableInstances
-           , GADTs
- #-}
-{-# LANGUAGE ConstraintKinds
-           , EmptyDataDecls
-           , FlexibleContexts
-           , FlexibleInstances
-           , FunctionalDependencies
-           , GADTs
-           , MultiParamTypeClasses
-           , OverloadedStrings
-           , UndecidableInstances
-           , ScopedTypeVariables
-           , InstanceSigs
-           , Rank2Types
-           , CPP
- #-}
--- | This is an internal module, anything exported by this module
--- may change without a major version bump.  Please use only
--- "Database.Esqueleto" if possible.
-module Database.Esqueleto.Internal.Sql
-  ( -- * The pretty face
-    SqlQuery
-  , SqlExpr(..)
-  , SqlEntity
-  , select
-  , selectSource
-  , delete
-  , deleteCount
-  , update
-  , updateCount
-  , insertSelect
-  , insertSelectCount
-    -- * The guts
-  , unsafeSqlCase
-  , unsafeSqlBinOp
-  , unsafeSqlBinOpComposite
-  , unsafeSqlValue
-  , unsafeSqlCastAs
-  , unsafeSqlFunction
-  , unsafeSqlExtractSubField
-  , UnsafeSqlFunctionArgument
-  , OrderByClause
-  , rawSelectSource
-  , runSource
-  , rawEsqueleto
-  , toRawSql
-  , Mode(..)
-  , NeedParens(..)
-  , IdentState
-  , renderExpr
-  , initialIdentState
-  , IdentInfo
-  , SqlSelect(..)
-  , veryUnsafeCoerceSqlExprValue
-  , veryUnsafeCoerceSqlExprValueList
-  -- * Helper functions
-  , renderQueryToText
-  , renderQuerySelect
-  , renderQueryUpdate
-  , renderQueryDelete
-  , renderQueryInsertInto
-  , makeOrderByNoNewline
-  , uncommas'
-  , parens
-  , toArgList
-  , builderToText
-  , Ident(..)
-  ) where
-
-import Database.Esqueleto.Internal.Internal

src/Database/Esqueleto/Legacy.hs

@@ -0,0 +1,416 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE RankNTypes #-}
+
+-- | WARNING
+--
+-- This module is introduced in version @3.5.0.0@ to provide a smooth migration
+-- experience from this legacy syntax to the new and improved syntax. If you've
+-- imported this module, it means you've decided to use the old syntax for
+-- a little bit longer, rather than migrate to the new stuff. That's fine!
+--
+-- But you should know that this module, and all of the legacy syntax, will be
+-- completely removed from the library in version @4.0.0.0@.
+--
+-- The @esqueleto@ EDSL (embedded domain specific language).
+-- This module replaces @Database.Persist@, so instead of
+-- importing that module you should just import this one:
+--
+-- @
+-- -- For a module using just esqueleto.
+-- import Database.Esqueleto
+-- @
+--
+-- If you need to use @persistent@'s default support for queries
+-- as well, either import it qualified:
+--
+-- @
+-- -- For a module that mostly uses esqueleto.
+-- import Database.Esqueleto
+-- import qualified Database.Persist as P
+-- @
+--
+-- or import @esqueleto@ itself qualified:
+--
+-- @
+-- -- For a module that uses esqueleto just on some queries.
+-- import Database.Persist
+-- import qualified Database.Esqueleto as E
+-- @
+--
+-- Other than identifier name clashes, @esqueleto@ does not
+-- conflict with @persistent@ in any way.
+module Database.Esqueleto.Legacy
+  ( -- * Setup
+    -- $setup
+
+    -- * Introduction
+    -- $introduction
+
+    -- * Getting started
+    -- $gettingstarted
+
+    -- * @esqueleto@'s Language
+    where_, on, groupBy, orderBy, rand, asc, desc, limit, offset
+             , distinct, distinctOn, don, distinctOnOrderBy, having, locking
+             , sub_select, (^.), (?.)
+             , val, isNothing, just, nothing, joinV, withNonNull
+             , countRows, count, countDistinct
+             , not_, (==.), (>=.), (>.), (<=.), (<.), (!=.), (&&.), (||.)
+             , between, (+.), (-.), (/.), (*.)
+             , random_, round_, ceiling_, floor_
+             , min_, max_, sum_, avg_, castNum, castNumM
+             , coalesce, coalesceDefault
+             , lower_, upper_, trim_, ltrim_, rtrim_, length_, left_, right_
+             , like, ilike, (%), concat_, (++.), castString
+             , subList_select, valList, justList
+             , in_, notIn, exists, notExists
+             , set, (=.), (+=.), (-=.), (*=.), (/=.)
+             , case_, toBaseId
+  , subSelect
+  , subSelectMaybe
+  , subSelectCount
+  , subSelectForeign
+  , subSelectList
+  , subSelectUnsafe
+  , ToBaseId(..)
+  , when_
+  , then_
+  , else_
+  , from
+  , Value(..)
+  , ValueList(..)
+  , OrderBy
+  , DistinctOn
+  , LockingKind(..)
+  , SqlString
+    -- ** Joins
+  , InnerJoin(..)
+  , CrossJoin(..)
+  , LeftOuterJoin(..)
+  , RightOuterJoin(..)
+  , FullOuterJoin(..)
+  , JoinKind(..)
+  , OnClauseWithoutMatchingJoinException(..)
+    -- * SQL backend
+  , SqlQuery
+  , SqlExpr
+  , SqlEntity
+  , select
+  , selectOne
+  , selectSource
+  , delete
+  , deleteCount
+  , update
+  , updateCount
+  , insertSelect
+  , insertSelectCount
+  , (<#)
+  , (<&>)
+  -- ** Rendering Queries
+  , renderQueryToText
+  , renderQuerySelect
+  , renderQueryUpdate
+  , renderQueryDelete
+  , renderQueryInsertInto
+    -- * Internal.Language
+  , From
+    -- * RDBMS-specific modules
+    -- $rdbmsSpecificModules
+
+    -- * Helpers
+  , valkey
+  , valJ
+  , associateJoin
+
+    -- * Re-exports
+    -- $reexports
+  , deleteKey
+  , module Database.Esqueleto.Internal.PersistentImport
+  ) where
+
+import Database.Esqueleto.Internal.Internal
+import Database.Esqueleto.Internal.PersistentImport
+
+
+-- $setup
+--
+-- If you're already using @persistent@, then you're ready to use
+-- @esqueleto@, no further setup is needed.  If you're just
+-- starting a new project and would like to use @esqueleto@, take
+-- a look at @persistent@'s book first
+-- (<http://www.yesodweb.com/book/persistent>) to learn how to
+-- define your schema.
+
+
+----------------------------------------------------------------------
+
+
+-- $introduction
+--
+-- The main goals of @esqueleto@ are to:
+--
+--   * Be easily translatable to SQL.  When you take a look at a
+--   @esqueleto@ query, you should be able to know exactly how
+--   the SQL query will end up.  (As opposed to being a
+--   relational algebra EDSL such as HaskellDB, which is
+--   non-trivial to translate into SQL.)
+--
+--   * Support the most widely used SQL features.  We'd like you to be
+--   able to use @esqueleto@ for all of your queries, no
+--   exceptions.  Send a pull request or open an issue on our
+--   project page (<https://github.com/prowdsponsor/esqueleto>) if
+--   there's anything missing that you'd like to see.
+--
+--   * Be as type-safe as possible.  We strive to provide as many
+--   type checks as possible.  If you get bitten by some invalid
+--   code that type-checks, please open an issue on our project
+--   page so we can take a look.
+--
+-- However, it is /not/ a goal to be able to write portable SQL.
+-- We do not try to hide the differences between DBMSs from you,
+-- and @esqueleto@ code that works for one database may not work
+-- on another.  This is a compromise we have to make in order to
+-- give you as much control over the raw SQL as possible without
+-- losing too much convenience.  This also means that you may
+-- type-check a query that doesn't work on your DBMS.
+
+
+----------------------------------------------------------------------
+
+
+-- $gettingstarted
+--
+-- We like clean, easy-to-read EDSLs.  However, in order to
+-- achieve this goal we've used a lot of type hackery, leading to
+-- some hard-to-read type signatures.  On this section, we'll try
+-- to build some intuition about the syntax.
+--
+-- For the following examples, we'll use this example schema:
+--
+-- @
+-- share [mkPersist sqlSettings, mkMigrate \"migrateAll\"] [persist|
+--   Person
+--     name String
+--     age Int Maybe
+--     deriving Eq Show
+--   BlogPost
+--     title String
+--     authorId PersonId
+--     deriving Eq Show
+--   Follow
+--     follower PersonId
+--     followed PersonId
+--     deriving Eq Show
+-- |]
+-- @
+--
+-- Most of @esqueleto@ was created with @SELECT@ statements in
+-- mind, not only because they're the most common but also
+-- because they're the most complex kind of statement.  The most
+-- simple kind of @SELECT@ would be:
+--
+-- @
+-- SELECT *
+-- FROM Person
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- do people <- 'select' $
+--              'from' $ \\person -> do
+--              return person
+--    liftIO $ mapM_ (putStrLn . personName . entityVal) people
+-- @
+--
+-- The expression above has type @SqlPersist m ()@, while
+-- @people@ has type @[Entity Person]@.  The query above will be
+-- translated into exactly the same query we wrote manually, but
+-- instead of @SELECT *@ it will list all entity fields (using
+-- @*@ is not robust).  Note that @esqueleto@ knows that we want
+-- an @Entity Person@ just because of the @personName@ that we're
+-- printing later.
+--
+-- However, most of the time we need to filter our queries using
+-- @WHERE@.  For example:
+--
+-- @
+-- SELECT *
+-- FROM Person
+-- WHERE Person.name = \"John\"
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- 'select' $
+-- 'from' $ \\p -> do
+-- 'where_' (p '^.' PersonName '==.' 'val' \"John\")
+-- return p
+-- @
+--
+-- Although @esqueleto@'s code is a bit more noisy, it's has
+-- almost the same structure (save from the @return@).  The
+-- @('^.')@ operator is used to project a field from an entity.
+-- The field name is the same one generated by @persistent@'s
+-- Template Haskell functions.  We use 'val' to lift a constant
+-- Haskell value into the SQL query.
+--
+-- Another example would be:
+--
+-- @
+-- SELECT *
+-- FROM Person
+-- WHERE Person.age >= 18
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- 'select' $
+-- 'from' $ \\p -> do
+-- 'where_' (p '^.' PersonAge '>=.' 'just' ('val' 18))
+-- return p
+-- @
+--
+-- Since @age@ is an optional @Person@ field, we use 'just' to lift
+-- @'val' 18 :: SqlExpr (Value Int)@ into @just ('val' 18) ::
+-- SqlExpr (Value (Maybe Int))@.
+--
+-- Implicit joins are represented by tuples.  For example, to get
+-- the list of all blog posts and their authors, we could write:
+--
+-- @
+-- SELECT BlogPost.*, Person.*
+-- FROM BlogPost, Person
+-- WHERE BlogPost.authorId = Person.id
+-- ORDER BY BlogPost.title ASC
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- 'select' $
+-- 'from' $ \\(b, p) -> do
+-- 'where_' (b '^.' BlogPostAuthorId '==.' p '^.' PersonId)
+-- 'orderBy' ['asc' (b '^.' BlogPostTitle)]
+-- return (b, p)
+-- @
+--
+-- However, you may want your results to include people who don't
+-- have any blog posts as well using a @LEFT OUTER JOIN@:
+--
+-- @
+-- SELECT Person.*, BlogPost.*
+-- FROM Person LEFT OUTER JOIN BlogPost
+-- ON Person.id = BlogPost.authorId
+-- ORDER BY Person.name ASC, BlogPost.title ASC
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- 'select' $
+-- 'from' $ \\(p `'LeftOuterJoin`` mb) -> do
+-- 'on' ('just' (p '^.' PersonId) '==.' mb '?.' BlogPostAuthorId)
+-- 'orderBy' ['asc' (p '^.' PersonName), 'asc' (mb '?.' BlogPostTitle)]
+-- return (p, mb)
+-- @
+--
+-- On a @LEFT OUTER JOIN@ the entity on the right hand side may
+-- not exist (i.e. there may be a @Person@ without any
+-- @BlogPost@s), so while @p :: SqlExpr (Entity Person)@, we have
+-- @mb :: SqlExpr (Maybe (Entity BlogPost))@.  The whole
+-- expression above has type @SqlPersist m [(Entity Person, Maybe
+-- (Entity BlogPost))]@.  Instead of using @(^.)@, we used
+-- @('?.')@ to project a field from a @Maybe (Entity a)@.
+--
+-- We are by no means limited to joins of two tables, nor by
+-- joins of different tables.  For example, we may want a list
+-- of the @Follow@ entity:
+--
+-- @
+-- SELECT P1.*, Follow.*, P2.*
+-- FROM Person AS P1
+-- INNER JOIN Follow ON P1.id = Follow.follower
+-- INNER JOIN Person AS P2 ON P2.id = Follow.followed
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+-- 'select' $
+-- 'from' $ \\(p1 `'InnerJoin`` f `'InnerJoin`` p2) -> do
+-- 'on' (p1 '^.' PersonId '==.' f '^.' FollowFollower)
+-- 'on' (p2 '^.' PersonId '==.' f '^.' FollowFollowed)
+-- return (p1, f, p2)
+-- @
+--
+-- We also currently support @UPDATE@ and @DELETE@ statements.
+-- For example:
+--
+-- @
+-- do 'update' $ \\p -> do
+--      'set' p [ PersonName '=.' 'val' \"João\" ]
+--      'where_' (p '^.' PersonName '==.' 'val' \"Joao\")
+--    'delete' $
+--      'from' $ \\p -> do
+--      'where_' (p '^.' PersonAge '<.' 'just' ('val' 14))
+-- @
+--
+-- The results of queries can also be used for insertions.
+-- In @SQL@, we might write the following, inserting a new blog
+-- post for every user:
+--
+-- @
+-- INSERT INTO BlogPost
+-- SELECT ('Group Blog Post', id)
+-- FROM Person
+-- @
+--
+-- In @esqueleto@, we may write the same query above as:
+--
+-- @
+--  'insertSelect' $ 'from' $ \\p->
+--  return $ BlogPost '<#' \"Group Blog Post\" '<&>' (p '^.' PersonId)
+-- @
+--
+-- Individual insertions can be performed through Persistent's
+-- 'insert' function, reexported for convenience.
+
+
+----------------------------------------------------------------------
+
+
+-- $reexports
+--
+-- We re-export many symbols from @persistent@ for convenince:
+--
+--  * \"Store functions\" from "Database.Persist".
+--
+--  * Everything from "Database.Persist.Class" except for
+--    @PersistQuery@ and @delete@ (use 'deleteKey' instead).
+--
+--  * Everything from "Database.Persist.Types" except for
+--    @Update@, @SelectOpt@, @BackendSpecificFilter@ and @Filter@.
+--
+--  * Everything from "Database.Persist.Sql" except for
+--    @deleteWhereCount@ and @updateWhereCount@.
+
+
+----------------------------------------------------------------------
+
+
+-- $rdbmsSpecificModules
+--
+-- There are many differences between SQL syntax and functions
+-- supported by different RDBMSs.  Since version 2.2.8,
+-- @esqueleto@ includes modules containing functions that are
+-- specific to a given RDBMS.
+--
+--  * PostgreSQL: "Database.Esqueleto.PostgreSQL".
+--
+-- In order to use these functions, you need to explicitly import
+-- their corresponding modules, they're not re-exported here.

src/Database/Esqueleto/MySQL.hs

@@ -1,14 +1,14 @@
 {-# LANGUAGE OverloadedStrings #-}
+
 -- | This module contain MySQL-specific functions.
 --
--- /Since: 2.2.8/
+-- @since 2.2.8
 module Database.Esqueleto.MySQL
-  ( random_
-  ) where
+    ( random_
+    ) where
 
-import Database.Esqueleto.Internal.Language hiding (random_)
+import Database.Esqueleto.Internal.Internal hiding (random_)
 import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Sql
 
 -- | (@random()@) Split out into database specific modules
 -- because MySQL uses `rand()`.

src/Database/Esqueleto/PostgreSQL.hs

@@ -1,59 +1,65 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE OverloadedStrings
-           , GADTs, CPP, Rank2Types
-           , ScopedTypeVariables
- #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE Rank2Types #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
 -- | This module contain PostgreSQL-specific functions.
 --
--- /Since: 2.2.8/
+-- @since: 2.2.8
 module Database.Esqueleto.PostgreSQL
-  ( AggMode(..)
-  , arrayAggDistinct
-  , arrayAgg
-  , arrayAggWith
-  , arrayRemove
-  , arrayRemoveNull
-  , stringAgg
-  , stringAggWith
-  , maybeArray
-  , chr
-  , now_
-  , random_
-  , upsert
-  , upsertBy
-  , insertSelectWithConflict
-  , insertSelectWithConflictCount
-  , filterWhere
-  -- * Internal
-  , unsafeSqlAggregateFunction
-  ) where
+    ( AggMode(..)
+    , arrayAggDistinct
+    , arrayAgg
+    , arrayAggWith
+    , arrayRemove
+    , arrayRemoveNull
+    , stringAgg
+    , stringAggWith
+    , maybeArray
+    , chr
+    , now_
+    , random_
+    , upsert
+    , upsertBy
+    , insertSelectWithConflict
+    , insertSelectWithConflictCount
+    , filterWhere
+    , values
+    -- * Internal
+    , unsafeSqlAggregateFunction
+    ) where
 
 #if __GLASGOW_HASKELL__ < 804
-import           Data.Semigroup
+import Data.Semigroup
 #endif
-import qualified Data.Text.Internal.Builder                   as TLB
-import           Data.Time.Clock                              (UTCTime)
-import           Database.Esqueleto.Internal.Language         hiding (random_)
-import           Database.Esqueleto.Internal.PersistentImport hiding (upsert, upsertBy)
-import           Database.Esqueleto.Internal.Sql
-import           Database.Esqueleto.Internal.Internal         (EsqueletoError(..), CompositeKeyError(..),
-                                                              UnexpectedCaseError(..), SetClause, Ident(..),
-                                                              uncommas, FinalResult(..), toUniqueDef,
-                                                              KnowResult, renderUpdates, UnexpectedValueError(..))
-import           Database.Persist.Class                       (OnlyOneUniqueKey)
-import           Data.List.NonEmpty                           ( NonEmpty( (:|) ) )
-import           Data.Int                                     (Int64)
-import           Data.Proxy                                   (Proxy(..))
-import           Control.Arrow                                ((***), first)
-import           Control.Exception                            (throw)
-import           Control.Monad                                (void)
-import           Control.Monad.IO.Class                       (MonadIO (..))
-import qualified Control.Monad.Trans.Reader                   as R
+import Control.Arrow (first)
+import Control.Exception (throw)
+import Control.Monad (void)
+import Control.Monad.IO.Class (MonadIO(..))
+import qualified Control.Monad.Trans.Reader as R
+import Data.Int (Int64)
+import qualified Data.List.NonEmpty as NE
+import Data.Maybe
+import Data.Proxy (Proxy(..))
+import qualified Data.Text.Internal.Builder as TLB
+import qualified Data.Text.Lazy as TL
+import Data.Time.Clock (UTCTime)
+import qualified Database.Esqueleto.Experimental as Ex
+import qualified Database.Esqueleto.Experimental.From as Ex
+import Database.Esqueleto.Internal.Internal hiding (random_)
+import Database.Esqueleto.Internal.PersistentImport hiding (upsert, upsertBy)
+import Database.Persist.Class (OnlyOneUniqueKey)
+import Database.Persist (ConstraintNameDB(..), EntityNameDB(..))
+import Database.Persist.SqlBackend
 
 -- | (@random()@) Split out into database specific modules
 -- because MySQL uses `rand()`.
 --
--- /Since: 2.6.0/
+-- @since 2.6.0
 random_ :: (PersistField a, Num a) => SqlExpr (Value a)
 random_ = unsafeSqlValue "RANDOM()"
 
@@ -69,45 +75,48 @@ maybeArray ::
 maybeArray x = coalesceDefault [x] (emptyArray)
 
 -- | Aggregate mode
-data AggMode = AggModeAll -- ^ ALL
-             | AggModeDistinct -- ^ DISTINCT
-  deriving (Show)
+data AggMode
+    = AggModeAll -- ^ ALL
+    | AggModeDistinct -- ^ DISTINCT
+    deriving (Show)
 
 -- | (Internal) Create a custom aggregate functions with aggregate mode
 --
 -- /Do/ /not/ use this function directly, instead define a new function and give
 -- it a type (see `unsafeSqlBinOp`)
-unsafeSqlAggregateFunction ::
-     UnsafeSqlFunctionArgument a
-  => TLB.Builder
-  -> AggMode
-  -> a
-  -> [OrderByClause]
-  -> SqlExpr (Value b)
-unsafeSqlAggregateFunction name mode args orderByClauses =
-  ERaw Never $ \info ->
+unsafeSqlAggregateFunction
+    :: UnsafeSqlFunctionArgument a
+    => TLB.Builder
+    -> AggMode
+    -> a
+    -> [OrderByClause]
+    -> SqlExpr (Value b)
+unsafeSqlAggregateFunction name mode args orderByClauses = ERaw noMeta $ \_ info ->
     let (orderTLB, orderVals) = makeOrderByNoNewline info orderByClauses
         -- Don't add a space if we don't have order by clauses
-        orderTLBSpace = case orderByClauses of
-                          [] -> ""
-                          (_:_) -> " "
+        orderTLBSpace =
+            case orderByClauses of
+                []    -> ""
+                (_:_) -> " "
         (argsTLB, argsVals) =
-          uncommas' $ map (\(ERaw _ f) -> f info) $ toArgList args
-        aggMode = case mode of
-                    AggModeAll -> "" -- ALL is the default, so we don't need to
-                                     -- specify it
-                    AggModeDistinct -> "DISTINCT "
+            uncommas' $ map (\(ERaw _ f) -> f Never info) $ toArgList args
+        aggMode =
+            case mode of
+                AggModeAll      -> ""
+                -- ALL is the default, so we don't need to
+                -- specify it
+                AggModeDistinct -> "DISTINCT "
     in ( name <> parens (aggMode <> argsTLB <> orderTLBSpace <> orderTLB)
        , argsVals <> orderVals
        )
 
 --- | (@array_agg@) Concatenate input values, including @NULL@s,
 --- into an array.
-arrayAggWith ::
-     AggMode
-  -> SqlExpr (Value a)
-  -> [OrderByClause]
-  -> SqlExpr (Value (Maybe [a]))
+arrayAggWith
+    :: AggMode
+    -> SqlExpr (Value a)
+    -> [OrderByClause]
+    -> SqlExpr (Value (Maybe [a]))
 arrayAggWith = unsafeSqlAggregateFunction "array_agg"
 
 --- | (@array_agg@) Concatenate input values, including @NULL@s,
@@ -118,18 +127,17 @@ arrayAgg x = arrayAggWith AggModeAll x []
 -- | (@array_agg@) Concatenate distinct input values, including @NULL@s, into
 -- an array.
 --
--- /Since: 2.5.3/
-arrayAggDistinct ::
-     (PersistField a, PersistField [a])
-  => SqlExpr (Value a)
-  -> SqlExpr (Value (Maybe [a]))
+-- @since 2.5.3
+arrayAggDistinct
+    :: (PersistField a, PersistField [a])
+    => SqlExpr (Value a)
+    -> SqlExpr (Value (Maybe [a]))
 arrayAggDistinct x = arrayAggWith AggModeDistinct x []
 
-
 -- | (@array_remove@) Remove all elements equal to the given value from the
 -- array.
 --
--- /Since: 2.5.3/
+-- @since 2.5.3
 arrayRemove :: SqlExpr (Value [a]) -> SqlExpr (Value a) -> SqlExpr (Value [a])
 arrayRemove arr elem' = unsafeSqlFunction "array_remove" (arr, elem')
 
@@ -154,7 +162,7 @@ stringAggWith mode expr delim os =
 -- | (@string_agg@) Concatenate input values separated by a
 -- delimiter.
 --
--- /Since: 2.2.8/
+-- @since 2.2.8
 stringAgg ::
      SqlString s
   => SqlExpr (Value s) -- ^ Input values.
@@ -165,21 +173,24 @@ stringAgg expr delim = stringAggWith AggModeAll expr delim []
 -- | (@chr@) Translate the given integer to a character. (Note the result will
 -- depend on the character set of your database.)
 --
--- /Since: 2.2.11/
+-- @since 2.2.11
 chr :: SqlString s => SqlExpr (Value Int) -> SqlExpr (Value s)
 chr = unsafeSqlFunction "chr"
 
 now_ :: SqlExpr (Value UTCTime)
 now_ = unsafeSqlFunction "NOW" ()
 
-upsert :: (MonadIO m,
-      PersistEntity record,
-      OnlyOneUniqueKey record,
-      PersistRecordBackend record SqlBackend,
-      IsPersistBackend (PersistEntityBackend record))
+upsert
+    ::
+    ( MonadIO m
+    , PersistEntity record
+    , OnlyOneUniqueKey record
+    , PersistRecordBackend record SqlBackend
+    , IsPersistBackend (PersistEntityBackend record)
+    )
     => record
     -- ^ new record to insert
-    -> [SqlExpr (Update record)]
+    -> [SqlExpr (Entity record) -> SqlExpr Update]
     -- ^ updates to perform if the record already exists
     -> R.ReaderT SqlBackend m (Entity record)
     -- ^ the record in the database after the operation
@@ -187,30 +198,49 @@ upsert record updates = do
     uniqueKey <- onlyUnique record
     upsertBy uniqueKey record updates
 
-upsertBy :: (MonadIO m,
-    PersistEntity record,
-    IsPersistBackend (PersistEntityBackend record))
-  => Unique record
-  -- ^ uniqueness constraint to find by
-  -> record
-  -- ^ new record to insert
-  -> [SqlExpr (Update record)]
-  -- ^ updates to perform if the record already exists
-  -> R.ReaderT SqlBackend m (Entity record)
-  -- ^ the record in the database after the operation
+upsertBy
+    ::
+    (MonadIO m
+    , PersistEntity record
+    , IsPersistBackend (PersistEntityBackend record)
+    )
+    => Unique record
+    -- ^ uniqueness constraint to find by
+    -> record
+    -- ^ new record to insert
+    -> [SqlExpr (Entity record) -> SqlExpr Update]
+    -- ^ updates to perform if the record already exists
+    -> R.ReaderT SqlBackend m (Entity record)
+    -- ^ the record in the database after the operation
 upsertBy uniqueKey record updates = do
-  sqlB <- R.ask
-  maybe
-    (throw (UnexpectedCaseErr OperationNotSupported)) -- Postgres backend should have connUpsertSql, if this error is thrown, check changes on persistent
-    (handler sqlB)
-    (connUpsertSql sqlB)
+    sqlB <- R.ask
+    case getConnUpsertSql sqlB of
+        Nothing ->
+            -- Postgres backend should have connUpsertSql, if this error is
+            -- thrown, check changes on persistent
+            throw (UnexpectedCaseErr OperationNotSupported)
+        Just upsertSql ->
+            handler sqlB upsertSql
   where
     addVals l = map toPersistValue (toPersistFields record) ++ l ++ persistUniqueToValues uniqueKey
     entDef = entityDef (Just record)
-    uDef = toUniqueDef uniqueKey
     updatesText conn = first builderToText $ renderUpdates conn updates
+#if MIN_VERSION_persistent(2,11,0)
+    uniqueFields = persistUniqueToFieldNames uniqueKey
+    handler sqlB upsertSql = do
+        let (updateText, updateVals) =
+                updatesText sqlB
+            queryText =
+                upsertSql entDef uniqueFields updateText
+            queryVals =
+                addVals updateVals
+        xs <- rawSql queryText queryVals
+        pure (head xs)
+#else
+    uDef = toUniqueDef uniqueKey
     handler conn f = fmap head $ uncurry rawSql $
-      (***) (f entDef (uDef :| [])) addVals $ updatesText conn
+        (***) (f entDef (uDef :| [])) addVals $ updatesText conn
+#endif
 
 -- | Inserts into a table the results of a query similar to 'insertSelect' but allows
 -- to update values that violate a constraint during insertions.
@@ -245,51 +275,52 @@ upsertBy uniqueKey record updates = do
 -- the conflicting value is updated to the current plus the excluded.
 --
 -- @since 3.1.3
-insertSelectWithConflict :: forall a m val. (
-    FinalResult a,
-    KnowResult a ~ (Unique val),
-    MonadIO m,
-    PersistEntity val) =>
-  a
-  -- ^ Unique constructor or a unique, this is used just to get the name of the postgres constraint, the value(s) is(are) never used, so if you have a unique "MyUnique 0", "MyUnique undefined" would work as well.
-  -> SqlQuery (SqlExpr (Insertion val))
-  -- ^ Insert query.
-  -> (SqlExpr (Entity val) -> SqlExpr (Entity val) -> [SqlExpr (Update val)])
-  -- ^ A list of updates to be applied in case of the constraint being violated. The expression takes the current and excluded value to produce the updates.
-  -> SqlWriteT m ()
-insertSelectWithConflict unique query = void . insertSelectWithConflictCount unique query
+insertSelectWithConflict
+    :: forall a m val
+     . (FinalResult a, KnowResult a ~ Unique val, MonadIO m, PersistEntity val)
+    => a
+    -- ^ Unique constructor or a unique, this is used just to get the name of
+    -- the postgres constraint, the value(s) is(are) never used, so if you have
+    -- a unique "MyUnique 0", "MyUnique undefined" would work as well.
+    -> SqlQuery (SqlExpr (Insertion val))
+    -- ^ Insert query.
+    -> (SqlExpr (Entity val) -> SqlExpr (Entity val) -> [SqlExpr (Entity val) -> SqlExpr Update])
+    -- ^ A list of updates to be applied in case of the constraint being
+    -- violated. The expression takes the current and excluded value to produce
+    -- the updates.
+    -> SqlWriteT m ()
+insertSelectWithConflict unique query a =
+    void $ insertSelectWithConflictCount unique query a
 
 -- | Same as 'insertSelectWithConflict' but returns the number of rows affected.
 --
 -- @since 3.1.3
-insertSelectWithConflictCount :: forall a val m. (
-    FinalResult a,
-    KnowResult a ~ (Unique val),
-    MonadIO m,
-    PersistEntity val) =>
-  a
-  -> SqlQuery (SqlExpr (Insertion val))
-  -> (SqlExpr (Entity val) -> SqlExpr (Entity val) -> [SqlExpr (Update val)])
-  -> SqlWriteT m Int64
+insertSelectWithConflictCount
+    :: forall a val m
+     . (FinalResult a, KnowResult a ~ Unique val, MonadIO m, PersistEntity val)
+    => a
+    -> SqlQuery (SqlExpr (Insertion val))
+    -> (SqlExpr (Entity val) -> SqlExpr (Entity val) -> [SqlExpr (Entity val) -> SqlExpr Update])
+    -> SqlWriteT m Int64
 insertSelectWithConflictCount unique query conflictQuery = do
-  conn <- R.ask
-  uncurry rawExecuteCount $
-    combine
-      (toRawSql INSERT_INTO (conn, initialIdentState) (fmap EInsertFinal query))
-      (conflict conn)
+    conn <- R.ask
+    uncurry rawExecuteCount $
+        combine
+            (toRawSql INSERT_INTO (conn, initialIdentState) query)
+            (conflict conn)
   where
     proxy :: Proxy val
     proxy = Proxy
     updates = conflictQuery entCurrent entExcluded
     combine (tlb1,vals1) (tlb2,vals2) = (builderToText (tlb1 `mappend` tlb2), vals1 ++ vals2)
-    entExcluded = EEntity $ I "excluded"
-    tableName = unDBName . entityDB . entityDef
-    entCurrent = EEntity $ I (tableName proxy)
+    entExcluded = unsafeSqlEntity (I "excluded")
+    tableName = unEntityNameDB . getEntityDBName . entityDef
+    entCurrent = unsafeSqlEntity (I (tableName proxy))
     uniqueDef = toUniqueDef unique
-    constraint = TLB.fromText . unDBName . uniqueDBName $ uniqueDef
+    constraint = TLB.fromText . unConstraintNameDB . uniqueDBName $ uniqueDef
     renderedUpdates :: (BackendCompatible SqlBackend backend) => backend -> (TLB.Builder, [PersistValue])
     renderedUpdates conn = renderUpdates conn updates
-    conflict conn = (foldr1 mappend ([
+    conflict conn = (mconcat ([
         TLB.fromText "ON CONFLICT ON CONSTRAINT \"",
         constraint,
         TLB.fromText "\" DO "
@@ -327,18 +358,81 @@ insertSelectWithConflictCount unique query conflictQuery = do
 --
 -- @since 3.3.3.3
 filterWhere
-  :: SqlExpr (Value a)
-  -- ^ Aggregate function
-  -> SqlExpr (Value Bool)
-  -- ^ Filter clause
-  -> SqlExpr (Value a)
-filterWhere aggExpr clauseExpr = ERaw Never $ \info ->
-  let (aggBuilder, aggValues) = case aggExpr of
-        ERaw _ aggF     -> aggF info
-        ECompositeKey _ -> throw $ CompositeKeyErr FilterWhereAggError
-      (clauseBuilder, clauseValues) = case clauseExpr of
-        ERaw _ clauseF  -> clauseF info
-        ECompositeKey _ -> throw $ CompositeKeyErr FilterWhereClauseError
-  in ( aggBuilder <> " FILTER (WHERE " <> clauseBuilder <> ")"
-     , aggValues <> clauseValues
-     )
+    :: SqlExpr (Value a)
+    -- ^ Aggregate function
+    -> SqlExpr (Value Bool)
+    -- ^ Filter clause
+    -> SqlExpr (Value a)
+filterWhere aggExpr clauseExpr = ERaw noMeta $ \_ info ->
+    let (aggBuilder, aggValues) = case aggExpr of
+            ERaw _ aggF     -> aggF Never info
+        (clauseBuilder, clauseValues) = case clauseExpr of
+            ERaw _ clauseF  -> clauseF Never info
+    in ( aggBuilder <> " FILTER (WHERE " <> clauseBuilder <> ")"
+       , aggValues <> clauseValues
+       )
+
+
+-- | Allows to use `VALUES (..)` in-memory set of values
+-- in RHS of `from` expressions. Useful for JOIN's on
+-- known values which also can be additionally preprocessed
+-- somehow on db side with usage of inner PostgreSQL capabilities.
+--
+--
+-- Example of usage:
+--
+-- @
+-- share [mkPersist sqlSettings] [persistLowerCase|
+--   User
+--     name Text
+--     age Int
+--     deriving Eq Show
+--
+-- select $ do
+--  bound :& user <- from $
+--      values (   (val (10 :: Int), val ("ten" :: Text))
+--            :| [ (val 20, val "twenty")
+--               , (val 30, val "thirty") ]
+--            )
+--      `InnerJoin` table User
+--      `on` (\((bound, _boundName) :& user) -> user^.UserAge >=. bound)
+--  groupBy bound
+--  pure (bound, count @Int $ user^.UserName)
+-- @
+--
+-- @since 3.5.2.3
+values :: (ToSomeValues a, Ex.ToAliasReference a, Ex.ToAlias a) => NE.NonEmpty a -> Ex.From a
+values exprs = Ex.From $ do
+    ident <- newIdentFor $ DBName "vq"
+    alias <- Ex.toAlias $ NE.head exprs
+    ref   <- Ex.toAliasReference ident alias
+    let aliasIdents = mapMaybe (\someVal -> case someVal of
+            SomeValue (ERaw aliasMeta _) -> sqlExprMetaAlias aliasMeta
+            ) $ toSomeValues ref
+    pure (ref, const $ mkExpr ident aliasIdents)
+  where
+    someValueToSql :: IdentInfo -> SomeValue -> (TLB.Builder, [PersistValue])
+    someValueToSql info (SomeValue expr) = materializeExpr info expr
+
+    mkValuesRowSql :: IdentInfo -> [SomeValue] -> (TLB.Builder, [PersistValue])
+    mkValuesRowSql info vs =
+        let materialized = someValueToSql info <$> vs
+            valsSql = TLB.toLazyText . fst <$> materialized
+            params = concatMap snd materialized
+        in (TLB.fromLazyText $ "(" <> TL.intercalate "," valsSql <> ")", params)
+
+    -- (VALUES (v11, v12,..), (v21, v22,..)) as "vq"("v1", "v2",..)
+    mkExpr :: Ident -> [Ident] -> IdentInfo -> (TLB.Builder, [PersistValue])
+    mkExpr valsIdent colIdents info =
+        let materialized = mkValuesRowSql info . toSomeValues <$> NE.toList exprs
+            (valsSql, params) =
+                ( TL.intercalate "," $ map (TLB.toLazyText . fst) materialized
+                , concatMap snd materialized
+                )
+            colsAliases = TL.intercalate "," (map (TLB.toLazyText . useIdent info) colIdents)
+        in
+            ( "(VALUES " <> TLB.fromLazyText valsSql <> ") AS "
+            <> useIdent info valsIdent
+            <> "(" <> TLB.fromLazyText colsAliases <> ")"
+            , params
+            )

src/Database/Esqueleto/PostgreSQL/JSON.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE OverloadedStrings #-}
+
 {-|
   This module contains PostgreSQL-specific JSON functions.
 
@@ -22,130 +23,127 @@
   @since 3.1.0
 -}
 module Database.Esqueleto.PostgreSQL.JSON
-  ( -- * JSONB Newtype
+    ( -- * JSONB Newtype
+      --
+      -- | With 'JSONB', you can use your Haskell types in your
+      -- database table models as long as your type has 'FromJSON'
+      -- and 'ToJSON' instances.
+      --
+      -- @
+      -- import Database.Persist.TH
+      --
+      -- share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistUpperCase|
+      --   Example
+      --     json (JSONB MyType)
+      -- |]
+      -- @
+      --
+      -- CAUTION: Remember that changing the 'FromJSON' instance
+      -- of your type might result in old data becoming unparsable!
+      -- You can use (@JSONB Data.Aeson.Value@) for unstructured/variable JSON.
+      JSONB(..)
+    , JSONBExpr
+    , jsonbVal
+    -- * JSONAccessor
+    , JSONAccessor(..)
+    -- * Arrow operators
     --
-    -- | With 'JSONB', you can use your Haskell types in your
-    -- database table models as long as your type has 'FromJSON'
-    -- and 'ToJSON' instances.
+    -- | /Better documentation included with individual functions/
+    --
+    -- The arrow operators are selection functions to select values
+    -- from JSON arrays or objects.
+    --
+    -- === PostgreSQL Documentation
+    --
+    -- /Requires PostgreSQL version >= 9.3/
     --
     -- @
-    -- import Database.Persist.TH
+    --      | Type   | Description                                |  Example                                         | Example Result
+    -- -----+--------+--------------------------------------------+--------------------------------------------------+----------------
+    --  ->  | int    | Get JSON array element (indexed from zero, | '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2 | {"c":"baz"}
+    --      |        | negative integers count from the end)      |                                                  |
+    --  ->  | text   | Get JSON object field by key               | '{"a": {"b":"foo"}}'::json->'a'                  | {"b":"foo"}
+    --  ->> | int    | Get JSON array element as text             | '[1,2,3]'::json->>2                              | 3
+    --  ->> | text   | Get JSON object field as text              | '{"a":1,"b":2}'::json->>'b'                      | 2
+    --  \#>  | text[] | Get JSON object at specified path          | '{"a": {"b":{"c": "foo"}}}'::json#>'{a,b}'       | {"c": "foo"}
+    --  \#>> | text[] | Get JSON object at specified path as text  | '{"a":[1,2,3],"b":[4,5,6]}'::json#>>'{a,2}'      | 3
+    -- @
+    , (->.)
+    , (->>.)
+    , (#>.)
+    , (#>>.)
+    -- * Filter operators
     --
-    -- share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistUpperCase|
-    --   Example
-    --     json (JSONB MyType)
-    -- |]
+    -- | /Better documentation included with individual functions/
+    --
+    -- These functions test certain properties of JSON values
+    -- and return booleans, so are mainly used in WHERE clauses.
+    --
+    -- === PostgreSQL Documentation
+    --
+    -- /Requires PostgreSQL version >= 9.4/
+    --
+    -- @
+    --     | Type   | Description                                                     |  Example
+    -- ----+--------+-----------------------------------------------------------------+---------------------------------------------------
+    --  \@> | jsonb  | Does the left JSON value contain within it the right value?     | '{"a":1, "b":2}'::jsonb \@> '{"b":2}'::jsonb
+    --  <\@ | jsonb  | Is the left JSON value contained within the right value?        | '{"b":2}'::jsonb <\@ '{"a":1, "b":2}'::jsonb
+    --  ?  | text   | Does the string exist as a top-level key within the JSON value? | '{"a":1, "b":2}'::jsonb ? 'b'
+    --  ?| | text[] | Do any of these array strings exist as top-level keys?          | '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'c']
+    --  ?& | text[] | Do all of these array strings exist as top-level keys?          | '["a", "b"]'::jsonb ?& array['a', 'b']
+    -- @
+    , (@>.)
+    , (<@.)
+    , (?.)
+    , (?|.)
+    , (?&.)
+    -- * Deletion and concatenation operators
+    --
+    -- | /Better documentation included with individual functions/
+    --
+    -- These operators change the shape of the JSON value and
+    -- also have the highest risk of throwing an exception.
+    -- Please read the descriptions carefully before using these functions.
+    --
+    -- === PostgreSQL Documentation
+    --
+    -- /Requires PostgreSQL version >= 9.5/
+    --
+    -- @
+    --     | Type    | Description                                                            |  Example
+    -- ----+---------+------------------------------------------------------------------------+-------------------------------------------------
+    --  || | jsonb   | Concatenate two jsonb values into a new jsonb value                    | '["a", "b"]'::jsonb || '["c", "d"]'::jsonb
+    --  -  | text    | Delete key/value pair or string element from left operand.             | '{"a": "b"}'::jsonb - 'a'
+    --     |         | Key/value pairs are matched based on their key value.                  |
+    --  -  | integer | Delete the array element with specified index (Negative integers count | '["a", "b"]'::jsonb - 1
+    --     |         | from the end). Throws an error if top level container is not an array. |
+    --  \#- | text[]  | Delete the field or element with specified path                        | '["a", {"b":1}]'::jsonb \#- '{1,b}'
+    --     |         | (for JSON arrays, negative integers count from the end)                |
     -- @
     --
-    -- CAUTION: Remember that changing the 'FromJSON' instance
-    -- of your type might result in old data becoming unparsable!
-    -- You can use (@JSONB Data.Aeson.Value@) for unstructured/variable JSON.
-    JSONB(..)
-  , JSONBExpr
-  , jsonbVal
-  -- * JSONAccessor
-  , JSONAccessor(..)
-  -- * Arrow operators
-  --
-  -- | /Better documentation included with individual functions/
-  --
-  -- The arrow operators are selection functions to select values
-  -- from JSON arrays or objects.
-  --
-  -- === PostgreSQL Documentation
-  --
-  -- /Requires PostgreSQL version >= 9.3/
-  --
-  -- @
-  --      | Type   | Description                                |  Example                                         | Example Result
-  -- -----+--------+--------------------------------------------+--------------------------------------------------+----------------
-  --  ->  | int    | Get JSON array element (indexed from zero, | '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2 | {"c":"baz"}
-  --      |        | negative integers count from the end)      |                                                  |
-  --  ->  | text   | Get JSON object field by key               | '{"a": {"b":"foo"}}'::json->'a'                  | {"b":"foo"}
-  --  ->> | int    | Get JSON array element as text             | '[1,2,3]'::json->>2                              | 3
-  --  ->> | text   | Get JSON object field as text              | '{"a":1,"b":2}'::json->>'b'                      | 2
-  --  \#>  | text[] | Get JSON object at specified path          | '{"a": {"b":{"c": "foo"}}}'::json#>'{a,b}'       | {"c": "foo"}
-  --  \#>> | text[] | Get JSON object at specified path as text  | '{"a":[1,2,3],"b":[4,5,6]}'::json#>>'{a,2}'      | 3
-  -- @
-  , (->.)
-  , (->>.)
-  , (#>.)
-  , (#>>.)
-  -- * Filter operators
-  --
-  -- | /Better documentation included with individual functions/
-  --
-  -- These functions test certain properties of JSON values
-  -- and return booleans, so are mainly used in WHERE clauses.
-  --
-  -- === PostgreSQL Documentation
-  --
-  -- /Requires PostgreSQL version >= 9.4/
-  --
-  -- @
-  --     | Type   | Description                                                     |  Example
-  -- ----+--------+-----------------------------------------------------------------+---------------------------------------------------
-  --  \@> | jsonb  | Does the left JSON value contain within it the right value?     | '{"a":1, "b":2}'::jsonb \@> '{"b":2}'::jsonb
-  --  <\@ | jsonb  | Is the left JSON value contained within the right value?        | '{"b":2}'::jsonb <\@ '{"a":1, "b":2}'::jsonb
-  --  ?  | text   | Does the string exist as a top-level key within the JSON value? | '{"a":1, "b":2}'::jsonb ? 'b'
-  --  ?| | text[] | Do any of these array strings exist as top-level keys?          | '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'c']
-  --  ?& | text[] | Do all of these array strings exist as top-level keys?          | '["a", "b"]'::jsonb ?& array['a', 'b']
-  -- @
-  , (@>.)
-  , (<@.)
-  , (?.)
-  , (?|.)
-  , (?&.)
-  -- * Deletion and concatenation operators
-  --
-  -- | /Better documentation included with individual functions/
-  --
-  -- These operators change the shape of the JSON value and
-  -- also have the highest risk of throwing an exception.
-  -- Please read the descriptions carefully before using these functions.
-  --
-  -- === PostgreSQL Documentation
-  --
-  -- /Requires PostgreSQL version >= 9.5/
-  --
-  -- @
-  --     | Type    | Description                                                            |  Example
-  -- ----+---------+------------------------------------------------------------------------+-------------------------------------------------
-  --  || | jsonb   | Concatenate two jsonb values into a new jsonb value                    | '["a", "b"]'::jsonb || '["c", "d"]'::jsonb
-  --  -  | text    | Delete key/value pair or string element from left operand.             | '{"a": "b"}'::jsonb - 'a'
-  --     |         | Key/value pairs are matched based on their key value.                  |
-  --  -  | integer | Delete the array element with specified index (Negative integers count | '["a", "b"]'::jsonb - 1
-  --     |         | from the end). Throws an error if top level container is not an array. |
-  --  \#- | text[]  | Delete the field or element with specified path                        | '["a", {"b":1}]'::jsonb \#- '{1,b}'
-  --     |         | (for JSON arrays, negative integers count from the end)                |
-  -- @
-  --
-  -- /Requires PostgreSQL version >= 10/
-  --
-  -- @
-  --     | Type    | Description                                                            |  Example
-  -- ----+---------+------------------------------------------------------------------------+-------------------------------------------------
-  --  -  | text[]  | Delete multiple key/value pairs or string elements from left operand.  | '{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]
-  --     |         | Key/value pairs are matched based on their key value.                  |
-  -- @
-  , (-.)
-  , (--.)
-  , (#-.)
-  , (||.)
-  ) where
+    -- /Requires PostgreSQL version >= 10/
+    --
+    -- @
+    --     | Type    | Description                                                            |  Example
+    -- ----+---------+------------------------------------------------------------------------+-------------------------------------------------
+    --  -  | text[]  | Delete multiple key/value pairs or string elements from left operand.  | '{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]
+    --     |         | Key/value pairs are matched based on their key value.                  |
+    -- @
+    , (-.)
+    , (--.)
+    , (#-.)
+    , (||.)
+    ) where
 
 import Data.Text (Text)
-import Database.Esqueleto.Internal.Language hiding ((?.), (-.), (||.))
+import Database.Esqueleto.Internal.Internal hiding ((-.), (?.), (||.))
 import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Sql
 import Database.Esqueleto.PostgreSQL.JSON.Instances
 
-
 infixl 6 ->., ->>., #>., #>>.
 infixl 6 @>., <@., ?., ?|., ?&.
 infixl 6 ||., -., --., #-.
 
-
 -- | /Requires PostgreSQL version >= 9.3/
 --
 -- This function extracts the jsonb value from a JSON array or object,

src/Database/Esqueleto/PostgreSQL/JSON/Instances.hs

@@ -4,6 +4,8 @@
 {-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# language DerivingStrategies #-}
+
 module Database.Esqueleto.PostgreSQL.JSON.Instances where
 
 import Data.Aeson (FromJSON(..), ToJSON(..), encode, eitherDecodeStrict)
@@ -13,28 +15,28 @@ import Data.String (IsString(..))
 import Data.Text (Text)
 import qualified Data.Text as T (concat, pack)
 import qualified Data.Text.Encoding as TE (decodeUtf8, encodeUtf8)
-import Database.Esqueleto (Value, just, val)
 import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Sql (SqlExpr)
+import Database.Esqueleto.Internal.Internal (SqlExpr, Value, just, val)
 import GHC.Generics (Generic)
 
-
 -- | Newtype wrapper around any type with a JSON representation.
 --
 -- @since 3.1.0
 newtype JSONB a = JSONB { unJSONB :: a }
-  deriving
-    ( Generic
-    , FromJSON
-    , ToJSON
-    , Eq
-    , Foldable
-    , Functor
-    , Ord
-    , Read
-    , Show
-    , Traversable
-    )
+    deriving stock
+        ( Generic
+        , Eq
+        , Foldable
+        , Functor
+        , Ord
+        , Read
+        , Show
+        , Traversable
+        )
+    deriving newtype
+        ( FromJSON
+        , ToJSON
+        )
 
 -- | 'SqlExpr' of a NULL-able 'JSONB' value. Hence the 'Maybe'.
 --
@@ -60,48 +62,49 @@ jsonbVal = just . val . JSONB
 -- JSONKey "name"
 --
 -- NOTE: DO NOT USE ANY OF THE 'Num' METHODS ON THIS TYPE!
-data JSONAccessor = JSONIndex Int
-                  | JSONKey Text
-  deriving (Generic, Eq, Show)
+data JSONAccessor
+    = JSONIndex Int
+    | JSONKey Text
+    deriving (Generic, Eq, Show)
 
 -- | I repeat, DO NOT use any method other than 'fromInteger'!
 instance Num JSONAccessor where
-  fromInteger = JSONIndex . fromInteger
-  negate (JSONIndex i) = JSONIndex $ negate i
-  negate (JSONKey _) = error "Can not negate a JSONKey"
-  (+) = numErr
-  (-) = numErr
-  (*) = numErr
-  abs = numErr
-  signum = numErr
+    fromInteger = JSONIndex . fromInteger
+    negate (JSONIndex i) = JSONIndex $ negate i
+    negate (JSONKey _) = error "Can not negate a JSONKey"
+    (+) = numErr
+    (-) = numErr
+    (*) = numErr
+    abs = numErr
+    signum = numErr
 
 numErr :: a
 numErr = error "Do not use 'Num' methods on JSONAccessors"
 
 instance IsString JSONAccessor where
-  fromString = JSONKey . T.pack
+    fromString = JSONKey . T.pack
 
 -- | @since 3.1.0
 instance (FromJSON a, ToJSON a) => PersistField (JSONB a) where
-  toPersistValue = PersistDbSpecific . BSL.toStrict . encode . unJSONB
-  fromPersistValue pVal = fmap JSONB $ case pVal of
-      PersistByteString bs -> first (badParse $ TE.decodeUtf8 bs) $ eitherDecodeStrict bs
-      PersistText t -> first (badParse t) $ eitherDecodeStrict (TE.encodeUtf8 t)
-      x -> Left $ fromPersistValueError "string or bytea" x
+    toPersistValue = PersistLiteralEscaped . BSL.toStrict . encode . unJSONB
+    fromPersistValue pVal = fmap JSONB $ case pVal of
+        PersistByteString bs -> first (badParse $ TE.decodeUtf8 bs) $ eitherDecodeStrict bs
+        PersistText t -> first (badParse t) $ eitherDecodeStrict (TE.encodeUtf8 t)
+        x -> Left $ fromPersistValueError "string or bytea" x
 
 -- | jsonb
 --
 -- @since 3.1.0
 instance (FromJSON a, ToJSON a) => PersistFieldSql (JSONB a) where
-  sqlType _ = SqlOther "JSONB"
+    sqlType _ = SqlOther "JSONB"
 
 badParse :: Text -> String -> Text
 badParse t = fromPersistValueParseError t . T.pack
 
 fromPersistValueError
-  :: Text -- ^ Database type(s), should appear different from Haskell name, e.g. "integer" or "INT", not "Int".
-  -> PersistValue -- ^ Incorrect value
-  -> Text -- ^ Error message
+    :: Text -- ^ Database type(s), should appear different from Haskell name, e.g. "integer" or "INT", not "Int".
+    -> PersistValue -- ^ Incorrect value
+    -> Text -- ^ Error message
 fromPersistValueError databaseType received = T.concat
     [ "Failed to parse Haskell newtype `JSONB a`; "
     , "expected ", databaseType
@@ -110,9 +113,9 @@ fromPersistValueError databaseType received = T.concat
     ]
 
 fromPersistValueParseError
-  :: Text -- ^ Received value
-  -> Text -- ^ Additional error
-  -> Text -- ^ Error message
+    :: Text -- ^ Received value
+    -> Text -- ^ Additional error
+    -> Text -- ^ Error message
 fromPersistValueParseError received err = T.concat
     [ "Failed to parse Haskell type `JSONB a`, "
     , "but received ", received

src/Database/Esqueleto/SQLite.hs

@@ -1,14 +1,14 @@
 {-# LANGUAGE OverloadedStrings #-}
+
 -- | This module contain SQLite-specific functions.
 --
--- /Since: 2.2.8/
+-- @since 2.2.8
 module Database.Esqueleto.SQLite
   ( random_
   ) where
 
-import Database.Esqueleto.Internal.Language hiding (random_)
+import Database.Esqueleto.Internal.Internal hiding (random_)
 import Database.Esqueleto.Internal.PersistentImport
-import Database.Esqueleto.Internal.Sql
 
 -- | (@random()@) Split out into database specific modules
 -- because MySQL uses `rand()`.

stack-8.10.yaml

@@ -0,0 +1,12 @@
+resolver: lts-17.8
+
+packages:
+  - '.'
+  - 'examples'
+
+extra-deps:
+- lift-type-0.1.0.1
+- persistent-2.13.0.0
+- persistent-sqlite-2.13.0.0
+- persistent-mysql-2.13.0.0
+- persistent-postgresql-2.13.0.0

stack-8.6.yaml

@@ -5,9 +5,11 @@ packages:
   - 'examples'
 
 extra-deps:
-  - persistent-2.10.0
-  - persistent-template-2.7.0
-  - persistent-mysql-2.10.0
-  - persistent-postgresql-2.10.0
-  - persistent-sqlite-2.10.0
-  - postgresql-simple-0.6.1
+  - git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+    subdirs:
+      - persistent
+      - persistent-template
+      - persistent-mysql
+      - persistent-postgresql
+      - persistent-sqlite

stack-8.8.yaml

@@ -1,5 +1,12 @@
-resolver: lts-16.14
+resolver: lts-16.31
 
 packages:
   - '.'
   - 'examples'
+
+extra-deps:
+- persistent-2.12.0.1
+- persistent-template-2.12.0.0
+- persistent-mysql-2.12.0.0
+- persistent-postgresql-2.12.0.0
+- persistent-sqlite-2.12.0.0

stack-8.8.yaml.lock

@@ -3,7 +3,72 @@
 # For more information, please see the documentation at:
 #   https://docs.haskellstack.org/en/stable/lock_files
 
-packages: []
+packages:
+- completed:
+    subdir: persistent
+    name: persistent
+    version: 2.11.0.0
+    git: https://github.com/yesodweb/persistent
+    pantry-tree:
+      size: 2099
+      sha256: cd4d895557a60b40543c4a6804d32346a1c14c39e28658bb6852d8f4904ef1de
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+  original:
+    subdir: persistent
+    git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+- completed:
+    subdir: persistent-template
+    name: persistent-template
+    version: '2.9'
+    git: https://github.com/yesodweb/persistent
+    pantry-tree:
+      size: 620
+      sha256: 0602872c9c38ccc6966b4a1fd1d102a345f94ad855077157d588536ee6803343
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+  original:
+    subdir: persistent-template
+    git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+- completed:
+    subdir: persistent-mysql
+    name: persistent-mysql
+    version: 2.10.3
+    git: https://github.com/yesodweb/persistent
+    pantry-tree:
+      size: 577
+      sha256: a3b9d2ef77af25dca203a4dbe2857b6a1d4e421bbe376f261288e9a8ebfda28f
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+  original:
+    subdir: persistent-mysql
+    git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+- completed:
+    subdir: persistent-postgresql
+    name: persistent-postgresql
+    version: 2.11.0.0
+    git: https://github.com/yesodweb/persistent
+    pantry-tree:
+      size: 907
+      sha256: 6f1ad1c5b0b22cf455c6b1b4551a749d21bb72042597450c8ef9ff1eb5a74782
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+  original:
+    subdir: persistent-postgresql
+    git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+- completed:
+    subdir: persistent-sqlite
+    name: persistent-sqlite
+    version: 2.11.0.0
+    git: https://github.com/yesodweb/persistent
+    pantry-tree:
+      size: 891
+      sha256: fc9106077e16b406a5a823c732e3b543822a530f2befc446e49acf68797f6d42
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
+  original:
+    subdir: persistent-sqlite
+    git: https://github.com/yesodweb/persistent
+    commit: 0b8f9f3305c9b60c947565de882abfbfd8cb5702
 snapshots:
 - completed:
     size: 532382

stack-nightly.yaml

@@ -1,4 +1,14 @@
-resolver: nightly-2020-09-20
+resolver: nightly-2022-03-29
+
 packages:
-  - '.'
+  - "."
   - 'examples'
+
+
+extra-deps:
+  - time-1.12.1
+  - base-compat-0.12.1
+  - directory-1.3.7.0
+  - process-1.6.14.0
+  - Cabal-3.6.3.0
+  - unix-2.7.2.2

stack-nightly.yaml.lock

@@ -3,10 +3,52 @@
 # For more information, please see the documentation at:
 #   https://docs.haskellstack.org/en/stable/lock_files
 
-packages: []
+packages:
+- completed:
+    hackage: time-1.12.1@sha256:af1fafc1fb66e3d0afb66fb5ab8629f74c038bebd42c234b581aff7abc201089,6295
+    pantry-tree:
+      size: 7208
+      sha256: 96205222b57c39156ee646d710a4100a119dc28f211c57cacaf741f6c1bb35da
+  original:
+    hackage: time-1.12.1
+- completed:
+    hackage: base-compat-0.12.1@sha256:20e50848d9dfee1523fafe8950060b04fae43d402c15553da5c7cacd116f7846,6960
+    pantry-tree:
+      size: 9038
+      sha256: 2f2c14615443954f117613d77835234b598718e611fb4cf4522e01980bf1bcbd
+  original:
+    hackage: base-compat-0.12.1
+- completed:
+    hackage: directory-1.3.7.0@sha256:d44788eac41268d951679fdcc343adc8a65fcf5b016bdf6c1f996bf78dde798e,2940
+    pantry-tree:
+      size: 3433
+      sha256: 2352834a6424cc8b462706c15e08bb721e120829b147b6d798eade4ebce425f5
+  original:
+    hackage: directory-1.3.7.0
+- completed:
+    hackage: process-1.6.14.0@sha256:b6ad76fd3f4bf133cdc2dc9176e23447f2a0a8e9316047d53154cd11f871446d,2845
+    pantry-tree:
+      size: 1544
+      sha256: 72300155a8fd5a91f6b25dfebb77db05aa27a0b866dbfb2d7098c5e4580ca105
+  original:
+    hackage: process-1.6.14.0
+- completed:
+    hackage: Cabal-3.6.3.0@sha256:ff97c442b0c679c1c9876acd15f73ac4f602b973c45bde42b43ec28265ee48f4,12459
+    pantry-tree:
+      size: 19757
+      sha256: b250a53bdb56844f047a2927833bb565b936a289abfa85dfc2a63148d776368a
+  original:
+    hackage: Cabal-3.6.3.0
+- completed:
+    hackage: unix-2.7.2.2@sha256:15f5365c5995634e45de1772b9504761504a310184e676bc2ef60a14536dbef9,3496
+    pantry-tree:
+      size: 3536
+      sha256: 36434ced74d679622d61b69e8d92e1bd632d9ef3e284c63094653b2e473b0553
+  original:
+    hackage: unix-2.7.2.2
 snapshots:
 - completed:
-    size: 467884
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/nightly/2020/1/24.yaml
-    sha256: 55c1a4fc9222bc3b8cf91461f38e2641da675a7296f06528f47340c19d0c6e85
-  original: nightly-2020-01-24
+    size: 539378
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/nightly/2022/3/29.yaml
+    sha256: c959441a05f6fa4d45ae6e258290f04d399245b8436263b4abb525c7f73da6a5
+  original: nightly-2022-03-29

stack.yaml

@@ -1 +1 @@
-stack-8.6.yaml
+stack-8.10.yaml

style-guide.md

@@ -0,0 +1,9 @@
+# Style Guide
+
+- Please use `stylish-haskell` on the project to keep imports consistent and
+  clean. We have a custom [`.stylish-haskell.yaml`](.stylish-haskell.yaml) file.
+  You can run `stylish-haskell` from vim with `:%! stylish-haskell`.
+- Four space indent.
+- Prefer indentation over any other form of alignment.
+- If text goes off the screen due to four space indentation, factor out
+  functions and values into names to reduce indentation.

test/Common/Test/Import.hs

@@ -0,0 +1,87 @@
+{-# LANGUAGE CPP, AllowAmbiguousTypes #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE EmptyDataDecls #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PartialTypeSignatures #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Common.Test.Import
+    ( module Common.Test.Import
+    , module X
+    ) where
+
+import System.Environment
+import Control.Applicative
+import Common.Test.Models as X
+import Database.Esqueleto.Experimental as X hiding (random_)
+import Test.Hspec as X
+import UnliftIO as X
+import Control.Monad
+import Test.QuickCheck
+import Data.Text  as X (Text)
+import Control.Monad.Trans.Reader as X (ReaderT, mapReaderT, ask)
+
+type SpecDb = SpecWith ConnectionPool
+
+asserting :: MonadIO f => IO () -> SqlPersistT f ()
+asserting a = liftIO a
+
+noExceptions :: Expectation
+noExceptions = pure ()
+
+itDb
+    :: (HasCallStack)
+    => String
+    -> SqlPersistT IO x
+    -> SpecDb
+itDb message action = do
+    it message $ \connection -> do
+        void $ testDb connection action
+
+propDb
+    :: (HasCallStack, Testable a)
+    => String
+    -> ((SqlPersistT IO () -> IO ()) -> a )
+    -> SpecDb
+propDb message action = do
+    it message $ \connection -> do
+        property (action (testDb connection))
+
+testDb :: ConnectionPool -> SqlPersistT IO a -> IO a
+testDb conn action =
+    liftIO $ flip runSqlPool conn $ do
+        a <- action
+        transactionUndo
+        pure a
+
+setDatabaseState
+    :: SqlPersistT IO a
+    -> SqlPersistT IO ()
+    -> SpecWith ConnectionPool
+    -> SpecWith ConnectionPool
+setDatabaseState create clean test =
+    beforeWith (\conn -> runSqlPool create conn >> pure conn) $
+    after (\conn -> runSqlPool clean conn) $
+    test
+
+isCI :: IO Bool
+isCI =  do
+    env <- getEnvironment
+    return $ case lookup "TRAVIS" env <|> lookup "CI" env of
+        Just "true" -> True
+        _ -> False

test/Common/Test/Models.hs

@@ -0,0 +1,189 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE EmptyDataDecls #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PartialTypeSignatures #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Common.Test.Models where
+
+import Data.Time
+import Database.Esqueleto.Experimental
+import Database.Persist.Sql
+import Database.Persist.TH
+
+share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistUpperCase|
+  Foo
+    name Int
+    Primary name
+    deriving Show Eq Ord
+  Bar
+    quux FooId
+    deriving Show Eq Ord
+  Baz
+    blargh FooId
+    deriving Show Eq
+  Shoop
+    baz BazId
+    deriving Show Eq
+  Asdf
+    shoop ShoopId
+    deriving Show Eq
+  Another
+    why BazId
+  YetAnother
+    argh ShoopId
+
+  Person
+    name String
+    age Int Maybe
+    weight Int Maybe
+    favNum Int
+    deriving Eq Show Ord
+  BlogPost
+    title String
+    authorId PersonId
+    deriving Eq Show
+  Comment
+    body String
+    blog BlogPostId
+    deriving Eq Show
+  CommentReply
+    body String
+    comment CommentId
+  Profile
+    name String
+    person PersonId
+    deriving Eq Show
+  Reply
+    guy PersonId
+    body String
+    deriving Eq Show
+
+  Lord
+    county String maxlen=100
+    dogs Int Maybe
+    Primary county
+    deriving Eq Show
+
+  Deed
+    contract String maxlen=100
+    ownerId LordId maxlen=100
+    Primary contract
+    deriving Eq Show
+
+  Follow
+    follower PersonId
+    followed PersonId
+    deriving Eq Show
+
+  CcList
+    names [String]
+
+  Frontcover
+    number Int
+    title String
+    Primary number
+    deriving Eq Show
+  Article
+    title String
+    frontcoverNumber Int
+    Foreign Frontcover fkfrontcover frontcoverNumber
+    deriving Eq Show
+  ArticleMetadata
+    articleId ArticleId
+    Primary articleId
+    deriving Eq Show
+  Tag
+    name String maxlen=100
+    Primary name
+    deriving Eq Show
+  ArticleTag
+    articleId ArticleId
+    tagId     TagId maxlen=100
+    Primary   articleId tagId
+    deriving Eq Show
+  Article2
+    title String
+    frontcoverId FrontcoverId
+    deriving Eq Show
+  Point
+    x Int
+    y Int
+    name String
+    Primary x y
+    deriving Eq Show
+  Circle
+    centerX Int
+    centerY Int
+    name String
+    Foreign Point fkpoint centerX centerY
+    deriving Eq Show
+  Numbers
+    int    Int
+    double Double
+    deriving Eq Show
+
+  JoinOne
+    name    String
+    deriving Eq Show
+
+  JoinTwo
+    joinOne JoinOneId
+    name    String
+    deriving Eq Show
+
+  JoinThree
+    joinTwo JoinTwoId
+    name    String
+    deriving Eq Show
+
+  JoinFour
+    name    String
+    joinThree JoinThreeId
+    deriving Eq Show
+
+  JoinOther
+    name    String
+    deriving Eq Show
+
+  JoinMany
+    name      String
+    joinOther JoinOtherId
+    joinOne   JoinOneId
+    deriving Eq Show
+
+  DateTruncTest
+    created   UTCTime
+    deriving Eq Show
+|]
+
+-- Unique Test schema
+share [mkPersist sqlSettings, mkMigrate "migrateUnique"] [persistUpperCase|
+  OneUnique
+    name String
+    value Int
+    UniqueValue value
+    deriving Eq Show
+|]
+
+
+instance ToBaseId ArticleMetadata where
+    type BaseEnt ArticleMetadata = Article
+    toBaseIdWitness articleId = ArticleMetadataKey articleId
+

test/Common/Test/Select.hs

@@ -0,0 +1,22 @@
+module Common.Test.Select where
+
+import Common.Test.Import
+
+testSelect :: SpecDb
+testSelect = do
+    describe "select" $ do
+        itDb "works for a single value" $ do
+            ret <- select $ return $ val (3 :: Int)
+            asserting $ ret `shouldBe` [ Value 3 ]
+
+        itDb "works for a pair of a single value and ()" $ do
+            ret <- select $ return (val (3 :: Int), ())
+            asserting $ ret `shouldBe` [ (Value 3, ()) ]
+
+        itDb "works for a single ()" $ do
+            ret <- select $ return ()
+            asserting $ ret `shouldBe` [ () ]
+
+        itDb "works for a single NULL value" $ do
+            ret <- select $ return nothing
+            asserting $ ret `shouldBe` [ Value (Nothing :: Maybe Int) ]

test/MySQL/Test.hs

@@ -1,47 +1,40 @@
-{-# LANGUAGE ScopedTypeVariables
-           , FlexibleContexts
-           , RankNTypes
-           , TypeFamilies
-           , TypeApplications
-#-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
 
-module Main (main) where
+module MySQL.Test where
 
+import Common.Test.Import hiding (from, on)
+
+import Control.Applicative
 import Control.Monad (void)
 import Control.Monad.IO.Class (MonadIO(liftIO))
-import Control.Monad.Logger (runStderrLoggingT, runNoLoggingT)
-import Control.Monad.Trans.Reader (ReaderT)
-import Database.Persist.MySQL ( withMySQLConn
-                              , connectHost
-                              , connectDatabase
-                              , connectUser
-                              , connectPassword
-                              , defaultConnectInfo)
+import Control.Monad.Logger (runNoLoggingT, runStderrLoggingT)
+import Control.Monad.Trans.Reader (ReaderT, mapReaderT)
+import qualified Control.Monad.Trans.Resource as R
 import Database.Esqueleto
 import Database.Esqueleto.Experimental hiding (from, on)
 import qualified Database.Esqueleto.Experimental as Experimental
-import qualified Control.Monad.Trans.Resource as R
+import Database.Persist.MySQL
+       ( connectDatabase
+       , connectHost
+       , connectPassword
+       , connectPort
+       , connectUser
+       , defaultConnectInfo
+       , withMySQLConn
+       , createMySQLPool
+       )
+
 import Test.Hspec
 
 import Common.Test
 
-
--- testMysqlRandom :: Spec
--- testMysqlRandom = do
---   -- This is known not to work until
---   -- we can differentiate behavior by database
---   it "works with random_" $
---     run $ do
---       _ <- select $ return (random_ :: SqlExpr (Value Double))
---       return ()
-
-
-
-
-testMysqlSum :: Spec
+testMysqlSum :: SpecDb
 testMysqlSum = do
-  it "works with sum_" $
-    run $ do
+  itDb "works with sum_" $ do
       _ <- insert' p1
       _ <- insert' p2
       _ <- insert' p3
@@ -51,13 +44,9 @@ testMysqlSum = do
              return $ joinV $ sum_ (p ^. PersonAge)
       liftIO $ ret `shouldBe` [ Value $ Just (36 + 17 + 17 :: Double ) ]
 
-
-
-
-testMysqlTwoAscFields :: Spec
+testMysqlTwoAscFields :: SpecDb
 testMysqlTwoAscFields = do
-  it "works with two ASC fields (one call)" $
-    run $ do
+  itDb "works with two ASC fields (one call)" $ do
       p1e <- insert' p1
       p2e <- insert' p2
       p3e <- insert' p3
@@ -68,13 +57,9 @@ testMysqlTwoAscFields = do
              return p
       liftIO $ ret `shouldBe` [ p2e, p4e, p3e, p1e ]
 
-
-
-
-testMysqlOneAscOneDesc :: Spec
+testMysqlOneAscOneDesc :: SpecDb
 testMysqlOneAscOneDesc = do
-  it "works with one ASC and one DESC field (two calls)" $
-    run $ do
+  itDb "works with one ASC and one DESC field (two calls)" $ do
       p1e <- insert' p1
       p2e <- insert' p2
       p3e <- insert' p3
@@ -89,10 +74,9 @@ testMysqlOneAscOneDesc = do
 
 
 
-testMysqlCoalesce :: Spec
+testMysqlCoalesce :: SpecDb
 testMysqlCoalesce = do
-  it "works on PostgreSQL and MySQL with <2 arguments" $
-    run $ do
+  itDb "works on PostgreSQL and MySQL with <2 arguments" $ do
       _ :: [Value (Maybe Int)] <-
         select $
         from $ \p -> do
@@ -102,10 +86,9 @@ testMysqlCoalesce = do
 
 
 
-testMysqlUpdate :: Spec
+testMysqlUpdate :: SpecDb
 testMysqlUpdate = do
-  it "works on a simple example" $
-    run $ do
+  itDb "works on a simple example" $ do
       p1k <- insert p1
       p2k <- insert p2
       p3k <- insert p3
@@ -128,20 +111,13 @@ testMysqlUpdate = do
                               , Entity p1k (Person anon (Just 73) Nothing 1)
                               , Entity p3k p3 ]
 
-
-
-
-nameContains :: (BaseBackend backend ~ SqlBackend,
-                 BackendCompatible SqlBackend backend,
-                 MonadIO m, SqlString s,
-                 IsPersistBackend backend, PersistQueryRead backend,
-                 PersistUniqueRead backend)
+nameContains :: (SqlString s)
              => (SqlExpr (Value [Char])
              -> SqlExpr (Value s)
              -> SqlExpr (Value Bool))
              -> s
              -> [Entity Person]
-             -> ReaderT backend m ()
+             -> SqlPersistT IO ()
 nameContains f t expected = do
   ret <- select $
          from $ \p -> do
@@ -153,22 +129,20 @@ nameContains f t expected = do
   liftIO $ ret `shouldBe` expected
 
 
-testMysqlTextFunctions :: Spec
+testMysqlTextFunctions :: SpecDb
 testMysqlTextFunctions = do
   describe "text functions" $ do
-    it "like, (%) and (++.) work on a simple example" $
-       run $ do
+    itDb "like, (%) and (++.) work on a simple example" $ do
          [p1e, p2e, p3e, p4e] <- mapM insert' [p1, p2, p3, p4]
          nameContains like "h"  [p1e, p2e]
          nameContains like "i"  [p4e, p3e]
          nameContains like "iv" [p4e]
 
 
-testMysqlUnionWithLimits :: Spec
+testMysqlUnionWithLimits :: SpecDb
 testMysqlUnionWithLimits = do
   describe "MySQL Union" $ do
-    it "supports limit/orderBy by parenthesizing" $ do
-      run $ do
+    itDb "supports limit/orderBy by parenthesizing" $ do
         mapM_ (insert . Foo) [1..6]
 
         let q1 = do
@@ -186,61 +160,64 @@ testMysqlUnionWithLimits = do
               pure $ foo ^. FooName
 
 
-        ret <- select $ Experimental.from $ SelectQuery q1 `Union` SelectQuery q2
+        ret <- select $ Experimental.from $ q1 `union_` q2
         liftIO $ ret `shouldMatchList` [Value 1, Value 2, Value 4, Value 5]
 
-
-main :: IO ()
-main = do
-  hspec $ do
-    tests run
-
-    describe "Test MySQL locking" $ do
-      testLocking withConn
+spec :: Spec
+spec = beforeAll mkConnectionPool $ do
+    tests
 
     describe "MySQL specific tests" $ do
-      -- definitely doesn't work at the moment
-      -- testMysqlRandom
-      testMysqlSum
-      testMysqlTwoAscFields
-      testMysqlOneAscOneDesc
-      testMysqlCoalesce
-      testMysqlUpdate
-      testMysqlTextFunctions
-      testMysqlUnionWithLimits
-
-
-
-
-run, runSilent, runVerbose :: Run
-runSilent  act = runNoLoggingT     $ run_worker act
-runVerbose act = runStderrLoggingT $ run_worker act
-run =
-  if verbose
-  then runVerbose
-  else runSilent
-
+        -- definitely doesn't work at the moment
+        -- testMysqlRandom
+        testMysqlSum
+        testMysqlTwoAscFields
+        testMysqlOneAscOneDesc
+        testMysqlCoalesce
+        testMysqlUpdate
+        testMysqlTextFunctions
+        testMysqlUnionWithLimits
 
 verbose :: Bool
 verbose = False
 
-
-run_worker :: RunDbMonad m => SqlPersistT (R.ResourceT m) a -> m a
-run_worker act = withConn $ runSqlConn (migrateIt >> act)
-
-
-migrateIt :: RunDbMonad m => SqlPersistT (R.ResourceT m) ()
+migrateIt :: R.MonadUnliftIO m => SqlPersistT m ()
 migrateIt = do
-  void $ runMigrationSilent migrateAll
+  mapReaderT R.runResourceT $ void $ runMigrationSilent migrateAll
   cleanDB
 
+mkConnectionPool :: IO ConnectionPool
+mkConnectionPool = do
+    ci <- isCI
+    let connInfo
+            | ci =
+                defaultConnectInfo
+                    { connectHost     = "127.0.0.1"
+                    , connectUser     = "travis"
+                    , connectPassword = "esqutest"
+                    , connectDatabase = "esqutest"
+                    , connectPort     = 33306
+                    }
+            | otherwise =
+                defaultConnectInfo
+                    { connectHost     = "localhost"
+                    , connectUser     = "travis"
+                    , connectPassword = "esqutest"
+                    , connectDatabase = "esqutest"
+                    , connectPort     = 3306
+                    }
+    pool <-
+        if verbose
+        then
+            runStderrLoggingT $
+                createMySQLPool connInfo 4
+        else
+            runNoLoggingT $
+                createMySQLPool connInfo 4
 
-withConn :: RunDbMonad m => (SqlBackend -> R.ResourceT m a) -> m a
-withConn =
-  R.runResourceT .
-  withMySQLConn defaultConnectInfo
-    { connectHost     = "localhost"
-    , connectUser     = "travis"
-    , connectPassword = ""
-    , connectDatabase = "esqutest"
-    }
+
+    flip runSqlPool pool $ do
+        migrateIt
+        cleanDB
+
+    pure pool

test/PostgreSQL/MigrateJSON.hs

@@ -1,36 +1,36 @@
-{-# LANGUAGE FlexibleContexts
-           , GADTs
-           , GeneralizedNewtypeDeriving
-           , DerivingStrategies
-           , StandaloneDeriving
-           , MultiParamTypeClasses
-           , OverloadedStrings
-           , QuasiQuotes
-           , RankNTypes
-           , ScopedTypeVariables
-           , TemplateHaskell
-           , TypeFamilies
-           , UndecidableInstances
- #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+
 module PostgreSQL.MigrateJSON where
 
-import Control.Monad.Trans.Resource (ResourceT)
-import Data.Aeson (Value)
-import Database.Esqueleto (SqlExpr, delete, from)
-import Database.Esqueleto.PostgreSQL.JSON (JSONB)
-import Database.Persist (Entity)
-import Database.Persist.Sql (SqlPersistT)
-import Database.Persist.TH
+import Common.Test.Import hiding (Value, from, on)
 
-import Common.Test (RunDbMonad)
+import Data.Aeson (Value)
+import Database.Esqueleto.Legacy (from)
+import Database.Esqueleto.PostgreSQL.JSON (JSONB)
+import Database.Persist.TH
 
 -- JSON Table for PostgreSQL
 share [mkPersist sqlSettings, mkMigrate "migrateJSON"] [persistUpperCase|
 Json
   value (JSONB Value)
+  deriving Show
 |]
 
 cleanJSON
-  :: (forall m. RunDbMonad m
-  => SqlPersistT (ResourceT m) ())
+    :: forall m. MonadIO m
+    => SqlPersistT m ()
 cleanJSON = delete $ from $ \(_ :: SqlExpr (Entity Json)) -> return ()

test/SQLite/Test.hs

@@ -1,181 +1,140 @@
-{-# LANGUAGE ScopedTypeVariables
-           , FlexibleContexts
-           , RankNTypes
-           , TypeFamilies
-           , OverloadedStrings
-#-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
 
-module Main (main) where
+module SQLite.Test where
+
+import Common.Test.Import hiding (from, on)
 
 import Control.Monad (void)
-import Control.Monad.IO.Class (MonadIO(liftIO))
-import Control.Monad.Logger (runStderrLoggingT, runNoLoggingT)
-import Control.Monad.Trans.Reader (ReaderT)
-import Database.Persist.Sqlite (withSqliteConn)
-import Database.Sqlite (SqliteException)
-import Database.Esqueleto hiding (random_)
+import Control.Monad.Logger (runNoLoggingT, runStderrLoggingT)
+import Database.Esqueleto.Legacy hiding (random_)
 import Database.Esqueleto.SQLite (random_)
-import qualified Control.Monad.Trans.Resource as R
-import Test.Hspec
+import Database.Persist.Sqlite (createSqlitePool)
+import Database.Sqlite (SqliteException)
 
 import Common.Test
 
-
-
-
-testSqliteRandom :: Spec
+testSqliteRandom :: SpecDb
 testSqliteRandom = do
-  it "works with random_" $
-    run $ do
-      _ <- select $ return (random_ :: SqlExpr (Value Int))
-      return ()
+    itDb "works with random_" $ do
+        _ <- select $ return (random_ :: SqlExpr (Value Int))
+        asserting noExceptions
 
-
-
-
-
-testSqliteSum :: Spec
+testSqliteSum :: SpecDb
 testSqliteSum = do
-  it "works with sum_" $
-    run $ do
-      _ <- insert' p1
-      _ <- insert' p2
-      _ <- insert' p3
-      _ <- insert' p4
-      ret <- select $
-             from $ \p->
-             return $ joinV $ sum_ (p ^. PersonAge)
-      liftIO $ ret `shouldBe` [ Value $ Just (36 + 17 + 17 :: Int) ]
+    itDb "works with sum_" $ do
+        _ <- insert' p1
+        _ <- insert' p2
+        _ <- insert' p3
+        _ <- insert' p4
+        ret <- select $
+               from $ \p->
+               return $ joinV $ sum_ (p ^. PersonAge)
+        asserting $ ret `shouldBe` [ Value $ Just (36 + 17 + 17 :: Int) ]
 
 
 
 
 
-testSqliteTwoAscFields :: Spec
+testSqliteTwoAscFields :: SpecDb
 testSqliteTwoAscFields = do
-  it "works with two ASC fields (one call)" $
-    run $ do
-      p1e <- insert' p1
-      p2e <- insert' p2
-      p3e <- insert' p3
-      p4e <- insert' p4
-      ret <- select $
-             from $ \p -> do
-             orderBy [asc (p ^. PersonAge), asc (p ^. PersonName)]
-             return p
-      -- in SQLite and MySQL, its the reverse
-      liftIO $ ret `shouldBe` [ p2e, p4e, p3e, p1e ]
+    itDb "works with two ASC fields (one call)" $ do
+        p1e <- insert' p1
+        p2e <- insert' p2
+        p3e <- insert' p3
+        p4e <- insert' p4
+        ret <- select $
+               from $ \p -> do
+               orderBy [asc (p ^. PersonAge), asc (p ^. PersonName)]
+               return p
+        -- in SQLite and MySQL, its the reverse
+        asserting $ ret `shouldBe` [ p2e, p4e, p3e, p1e ]
 
-
-
-
-
-testSqliteOneAscOneDesc :: Spec
+testSqliteOneAscOneDesc :: SpecDb
 testSqliteOneAscOneDesc = do
-  it "works with one ASC and one DESC field (two calls)" $
-    run $ do
-      p1e <- insert' p1
-      p2e <- insert' p2
-      p3e <- insert' p3
-      p4e <- insert' p4
-      ret <- select $
-             from $ \p -> do
-             orderBy [desc (p ^. PersonAge)]
-             orderBy [asc (p ^. PersonName)]
-             return p
-      liftIO $ ret `shouldBe` [ p1e, p4e, p3e, p2e ]
+    itDb "works with one ASC and one DESC field (two calls)" $ do
+        p1e <- insert' p1
+        p2e <- insert' p2
+        p3e <- insert' p3
+        p4e <- insert' p4
+        ret <- select $
+               from $ \p -> do
+               orderBy [desc (p ^. PersonAge)]
+               orderBy [asc (p ^. PersonName)]
+               return p
+        asserting $ ret `shouldBe` [ p1e, p4e, p3e, p2e ]
 
-
-
-
-
-testSqliteCoalesce :: Spec
+testSqliteCoalesce :: SpecDb
 testSqliteCoalesce = do
-  it "throws an exception on SQLite with <2 arguments" $
-    run (select $
-         from $ \p -> do
-         return (coalesce [p ^. PersonAge]) :: SqlQuery (SqlExpr (Value (Maybe Int))))
-    `shouldThrow` (\(_ :: SqliteException) -> True)
+    itDb "throws an exception on SQLite with <2 arguments" $ do
+        eres <- try $ select $
+               from $ \p -> do
+               return (coalesce [p ^. PersonAge]) :: SqlQuery (SqlExpr (Value (Maybe Int)))
+        asserting $ case eres of
+            Left (_ :: SqliteException) ->
+                pure ()
+            Right _ ->
+                expectationFailure "Expected SqliteException with <2 args to coalesce"
 
-
-
-
-
-testSqliteUpdate :: Spec
+testSqliteUpdate :: SpecDb
 testSqliteUpdate = do
-  it "works on a simple example" $
-    run $ do
-      p1k <- insert p1
-      p2k <- insert p2
-      p3k <- insert p3
-      let anon = "Anonymous"
-      ()  <- update $ \p -> do
-             set p [ PersonName =. val anon
-                   , PersonAge *=. just (val 2) ]
-             where_ (p ^. PersonName !=. val "Mike")
-      n   <- updateCount $ \p -> do
-             set p [ PersonAge +=. just (val 1) ]
-             where_ (p ^. PersonName !=. val "Mike")
-      ret <- select $
-             from $ \p -> do
-             orderBy [ asc (p ^. PersonName), asc (p ^. PersonAge) ]
-             return p
-      -- SQLite: nulls appear first, update returns matched rows.
-      liftIO $ n `shouldBe` 2
-      liftIO $ ret `shouldBe` [ Entity p2k (Person anon Nothing (Just 37) 2)
-                              , Entity p1k (Person anon (Just 73) Nothing 1)
-                              , Entity p3k p3 ]
+    itDb "works on a simple example" $ do
+        p1k <- insert p1
+        p2k <- insert p2
+        p3k <- insert p3
+        let anon = "Anonymous" :: String
+        ()  <- update $ \p -> do
+               set p [ PersonName =. val anon
+                     , PersonAge *=. just (val 2) ]
+               where_ (p ^. PersonName !=. val "Mike")
+        n   <- updateCount $ \p -> do
+               set p [ PersonAge +=. just (val 1) ]
+               where_ (p ^. PersonName !=. val "Mike")
+        ret <- select $
+               from $ \p -> do
+               orderBy [ asc (p ^. PersonName), asc (p ^. PersonAge) ]
+               return p
+        -- SQLite: nulls appear first, update returns matched rows.
+        asserting $ do
+            n `shouldBe` 2
+            ret `shouldMatchList`
+                [ Entity p2k (Person anon Nothing (Just 37) 2)
+                , Entity p1k (Person anon (Just 73) Nothing 1)
+                , Entity p3k p3
+                ]
 
-
-
-
-
-nameContains :: (BaseBackend backend ~ SqlBackend,
-                 BackendCompatible SqlBackend backend,
-                 MonadIO m, SqlString s,
-                 IsPersistBackend backend, PersistQueryRead backend,
-                 PersistUniqueRead backend)
-             => (SqlExpr (Value [Char])
-             -> SqlExpr (Value s)
-             -> SqlExpr (Value Bool))
-             -> s
-             -> [Entity Person]
-             -> ReaderT backend m ()
-nameContains f t expected = do
-  ret <- select $
-         from $ \p -> do
-         where_ (f
-                  (p ^. PersonName)
-                  ((%) ++. val t ++. (%)))
-         orderBy [asc (p ^. PersonName)]
-         return p
-  liftIO $ ret `shouldBe` expected
-
-testSqliteTextFunctions :: Spec
+testSqliteTextFunctions :: SpecDb
 testSqliteTextFunctions = do
-  describe "text functions" $ do
-    it "like, (%) and (++.) work on a simple example" $
-       run $ do
-         [p1e, p2e, p3e, p4e] <- mapM insert' [p1, p2, p3, p4]
-         nameContains like "h"  [p1e, p2e]
-         nameContains like "i"  [p4e, p3e]
-         nameContains like "iv" [p4e]
+    describe "text functions" $ do
+        itDb "like, (%) and (++.) work on a simple example" $ do
+            let query :: String -> SqlPersistT IO [Entity Person]
+                query t =
+                    select $
+                    from $ \p -> do
+                    where_ (like
+                             (p ^. PersonName)
+                             ((%) ++. val t ++. (%)))
+                    orderBy [asc (p ^. PersonName)]
+                    return p
+            [p1e, p2e, p3e, p4e] <- mapM insert' [p1, p2, p3, p4]
+            r0 <- query "h"
+            r1 <- query "i"
+            r2 <- query "iv"
+            asserting $ do
+                r0 `shouldBe` [p1e, p2e]
+                r1 `shouldBe` [p4e, p3e]
+                r2 `shouldBe` [p4e]
 
-
-
-
-
-main :: IO ()
-main = do
-  hspec $ do
-    tests run
-
-    describe "Test SQLite locking" $ do
-      testLocking withConn
+spec :: HasCallStack => Spec
+spec = beforeAll mkConnectionPool $ do
+    tests
 
     describe "SQLite specific tests" $ do
-      testAscRandom random_ run
-      testRandomMath run
+      testAscRandom random_
+      testRandomMath
       testSqliteRandom
       testSqliteSum
       testSqliteTwoAscFields
@@ -184,32 +143,23 @@ main = do
       testSqliteUpdate
       testSqliteTextFunctions
 
+mkConnectionPool :: IO ConnectionPool
+mkConnectionPool = do
+    conn <-
+        if verbose
+        then runStderrLoggingT $
+            createSqlitePool ".esqueleto-test.sqlite" 4
+        else runNoLoggingT $
+            createSqlitePool ".esqueleto-test.sqlite" 4
+    flip runSqlPool conn $ do
+        migrateIt
 
-
-
-
-run, runSilent, runVerbose :: Run
-runSilent  act = runNoLoggingT     $ run_worker act
-runVerbose act = runStderrLoggingT $ run_worker act
-run =
-  if verbose
-  then runVerbose
-  else runSilent
-
+    pure conn
 
 verbose :: Bool
 verbose = False
 
-
-run_worker :: RunDbMonad m => SqlPersistT (R.ResourceT m) a -> m a
-run_worker act = withConn $ runSqlConn (migrateIt >> act)
-
-
-migrateIt :: RunDbMonad m => SqlPersistT (R.ResourceT m) ()
+migrateIt :: MonadUnliftIO m => SqlPersistT m ()
 migrateIt = do
   void $ runMigrationSilent migrateAll
-
-
-withConn :: RunDbMonad m => (SqlBackend -> R.ResourceT m a) -> m a
-withConn =
-  R.runResourceT . withSqliteConn ":memory:"
+  cleanDB

test/Spec.hs

@@ -0,0 +1,22 @@
+module Main where
+
+import Test.Hspec
+import Test.Hspec.Core.Spec
+
+import qualified SQLite.Test as SQLite
+import qualified MySQL.Test as MySQL
+import qualified PostgreSQL.Test as Postgres
+
+main :: IO ()
+main = hspec spec
+
+spec :: Spec
+spec = do
+    parallel $ describe "Esqueleto" $ do
+        describe "SQLite" $ do
+            sequential $ SQLite.spec
+        describe "MySQL" $ do
+            sequential $ MySQL.spec
+        describe "Postgresql" $ do
+            sequential $ Postgres.spec
+