Add a -f option for reading files to process from another file or stdin

main/Main.hs

@@ -22,6 +22,7 @@ data Options = Options
     , evaluate   :: Bool
     , check      :: Bool
     , expression :: Maybe String
+    , fromFile   :: Maybe FilePath
     , filePaths  :: [FilePath]
     }
 
@@ -45,22 +46,43 @@ mainOptions = Options
         (   short 'e'
          <> long "expr"
          <> help "Expression to parse or evaluate"))
+    <*> optional (strOption
+        (   short 'f'
+         <> long "file"
+         <> help "Parse all of the files given in FILE; - means stdin"))
     <*> many (strArgument (metavar "FILE" <> help "Path of file to parse"))
 
 main :: IO ()
 main = do
     opts <- execParser optsDef
-    (eres, mpath) <- case expression opts of
-        Just s -> return (parseNixStringLoc s, Nothing)
-        Nothing  -> case filePaths opts of
-            []     -> (, Nothing) . parseNixStringLoc <$> getContents
-            ["-"]  -> (, Nothing) . parseNixStringLoc <$> getContents
-            [path] -> (, Just path) <$> parseNixFileLoc path
-            _      -> error "hnix doesn't support multiple path arguments yet"
+    case expression opts of
+        Just s -> handleResult opts Nothing (parseNixStringLoc s)
+        Nothing  -> case fromFile opts of
+            Just "-" ->
+                mapM_ (processFile opts) =<< (lines <$> getContents)
+            Just path ->
+                mapM_ (processFile opts) =<< (lines <$> readFile path)
+            Nothing -> case filePaths opts of
+                [] ->
+                    handleResult opts Nothing . parseNixStringLoc
+                        =<< getContents
+                ["-"] ->
+                    handleResult opts Nothing . parseNixStringLoc
+                        =<< getContents
+                paths ->
+                    mapM_ (processFile opts) paths
+  where
+    optsDef :: ParserInfo Options
+    optsDef = info (helper <*> mainOptions)
+                   (fullDesc <> progDesc "" <> header "hnix")
+
+    processFile opts path = do
+        eres <- parseNixFileLoc path
+        handleResult opts (Just path) eres
 
     -- print . printNix =<< Nix.eval [nix|1 + 3|]
 
-    case eres of
+    handleResult opts mpath = \case
         Failure err -> hPutStrLn stderr $ "Parse failed: " ++ show err
         Success expr -> do
             when (check opts) $
@@ -78,7 +100,3 @@ main = do
                          . renderPretty 0.4 80
                          . prettyNix
                          . stripAnnotation $ expr
-  where
-    optsDef :: ParserInfo Options
-    optsDef = info (helper <*> mainOptions)
-                   (fullDesc <> progDesc "" <> header "hnix")