Allow use if stack.yaml file is found

Main.hs

@@ -37,6 +37,9 @@ import System.Console.CmdArgs
 import qualified Data.Map.Strict as Map
 import qualified Data.Set as Set
 
+-- directory
+import System.Directory (doesFileExist)
+
 
 -- |
 --
@@ -75,8 +78,14 @@ main = do
 
   pid <-
     case maybePackage of
-      Nothing ->
+      Nothing -> do
-        Exit.die "Error: No Cabal file found."
+        stack <- doesFileExist "stack.yaml"
+        if stack
+          then do
+            putStrLn "Found stack.yaml..."
+            return Nothing
+          else
+            Exit.die "Error: No Cabal file found."
 
       Just PackageDescription{..} -> do
         putStrLn $
@@ -86,7 +95,7 @@ main = do
             <> "License: "
             <> display license
             <> ")"
-        return package
+        return (Just package)
 
   maybeDependencies <- getDependencies
 

licensor.cabal

@@ -55,6 +55,7 @@ executable licensor
     , Cabal >= 1.22 && < 1.25
     , cmdargs >= 0.10 && < 0.11
     , containers
+    , directory
     , licensor
   default-language:
       Haskell2010

src/Licensor.hs

@@ -114,9 +114,16 @@ getPackageDescription =
 --
 
 getDependencies :: IO (Maybe (Set PackageIdentifier))
-getDependencies =
+getDependencies = do
-  fmap Set.fromList . sequence . fmap simpleParse . lines
+  eitherDeps <-
-    <$> readProcess "stack" ["list-dependencies", "--separator", "-"] ""
+    Exception.try $ readProcess "stack" ["list-dependencies", "--separator", "-"] ""
+
+  case eitherDeps of
+    Left (_ :: IOError) ->
+      return Nothing
+
+    Right deps ->
+      return $ fmap Set.fromList $ sequence $ fmap simpleParse (lines deps)
 
 
 -- |
@@ -160,17 +167,20 @@ getPackageLicense p@PackageIdentifier{..} = do
 --
 
 orderPackagesByLicense
-  :: PackageIdentifier
+  :: Maybe PackageIdentifier
   -> Set PackageIdentifier
   -> IO (Map LiLicense (Set PackageIdentifier), Set PackageIdentifier)
-orderPackagesByLicense p =
+orderPackagesByLicense maybeP =
   let
+    cond =
+      maybe (const False) (==) maybeP
+
     insertPackage package orderedPackages' = do
       maybeLicense <- getPackageLicense package
 
       (orderedPackages, failed) <- orderedPackages'
       return $
-        if p == package
+        if cond package
           then
             (orderedPackages, failed)
           else