Also expose a function to retrieve source code while printing errors and logs and logs

src/Main.hs

@@ -9,8 +9,7 @@ import Options.Applicative (
     , short, strArgument, strOption, value
   )
 import Paths_SJW (version)
-import SJW (Source, compile, mainIs, source)
-import System.IO (stderr, hPutStrLn)
+import SJW (Source, compile, mainIs, source, sourceCode)
 
 data Config = Config {
       includes :: [String]
@@ -60,13 +59,10 @@ getSource (Config {includes, mainModuleName = Just moduleName, target}) =
 main :: IO ()
 main = do
   config@(Config {outputFile}) <- getConfig
-  result <- SJW.compile $ getSource config
+  result <- SJW.sourceCode =<< SJW.compile (getSource config)
   case result of
-    Left errorMessage -> printErr errorMessage
-    Right (sourceCode, logs) -> do
-      mapM_ printErr logs
-      output outputFile . Text.unpack $ sourceCode
+    Nothing -> return ()
+    Just code -> output outputFile $ Text.unpack code
   where
-    printErr = hPutStrLn stderr
     output "-" = putStr
     output fileName = writeFile fileName

src/SJW.hs

@@ -6,6 +6,7 @@ module SJW (
     , compile
     , mainIs
     , source
+    , sourceCode
   ) where
 
 import Control.Applicative ((<|>))
@@ -21,10 +22,13 @@ import SJW.Source (CodePath(..), Source(..), Path(..), source)
 import System.Directory (doesDirectoryExist)
 import System.Environment (lookupEnv)
 import System.FilePath ((</>))
+import System.IO (stderr, hPutStrLn)
 import System.Posix.User (getRealUserID, getUserEntryForID, homeDirectory)
 import Text.Printf (printf)
 
-compile :: Source -> IO (Either String (Text, [String]))
+type Result = Either String (Text, [String])
+
+compile :: Source -> IO Result
 compile inputSource = runExceptT $ do
   checkedPackages <- check packages
   let checkedSource = inputSource {code = CodePath checkedPackages}
@@ -35,6 +39,11 @@ compile inputSource = runExceptT $ do
         modules = Map.empty
       }
 
+sourceCode :: Result -> IO (Maybe Text)
+sourceCode (Left errorMessage) = hPutStrLn stderr errorMessage >> return Nothing
+sourceCode (Right (output, logs)) =
+  mapM_ (hPutStrLn stderr) logs >> return (Just output)
+
 mainIs :: Source -> String -> Source
 mainIs context dotSeparated = context {mainModule = read dotSeparated}