Don't silently ignore superfluous command line arguments

Author: nh2

GHCMod.hs

@@ -77,6 +77,7 @@ parseArgs spec argv
 ----------------------------------------------------------------
 
 data GHCModError = SafeList
+                 | TooManyArguments String
                  | NoSuchCommand String
                  | CmdArg [String]
                  | FileNotExist String deriving (Show, Typeable)
@@ -100,15 +101,19 @@ main = flip catches handlers $ do
         cmdArg2 = cmdArg !. 2
         cmdArg3 = cmdArg !. 3
         cmdArg4 = cmdArg !. 4
+        remainingArgs = tail cmdArg
+        nArgs n f = if length remainingArgs == n
+                        then f
+                        else throw (TooManyArguments cmdArg0)
     res <- case cmdArg0 of
-      "browse" -> concat <$> mapM (browseModule opt) (tail cmdArg)
+      "browse" -> concat <$> mapM (browseModule opt) remainingArgs
       "list"   -> listModules opt
-      "check"  -> withFile (checkSyntax opt cradle) cmdArg1
-      "expand" -> withFile (checkSyntax opt { expandSplice = True } cradle) cmdArg1
-      "debug"  -> withFile (debugInfo opt cradle strVer) cmdArg1
-      "type"   -> withFile (typeExpr opt cradle cmdArg2 (read cmdArg3) (read cmdArg4)) cmdArg1
-      "info"   -> withFile (infoExpr opt cradle cmdArg2 cmdArg3) cmdArg1
-      "lint"   -> withFile (lintSyntax opt) cmdArg1
+      "check"  -> nArgs 1 $ withFile (checkSyntax opt cradle) cmdArg1
+      "expand" -> nArgs 1 $ withFile (checkSyntax opt { expandSplice = True } cradle) cmdArg1
+      "debug"  -> nArgs 1 $ withFile (debugInfo opt cradle strVer) cmdArg1
+      "type"   -> nArgs 4 $ withFile (typeExpr opt cradle cmdArg2 (read cmdArg3) (read cmdArg4)) cmdArg1
+      "info"   -> nArgs 3 $ withFile (infoExpr opt cradle cmdArg2 cmdArg3) cmdArg1
+      "lint"   -> nArgs 1 $ withFile (lintSyntax opt) cmdArg1
       "lang"   -> listLanguages opt
       "flag"   -> listFlags opt
       "boot"   -> do
@@ -125,6 +130,9 @@ main = flip catches handlers $ do
     handler1 = print -- for debug
     handler2 :: GHCModError -> IO ()
     handler2 SafeList = printUsage
+    handler2 (TooManyArguments cmd) = do
+        hPutStrLn stderr $ "\"" ++ cmd ++ "\": Too many arguments"
+        printUsage
     handler2 (NoSuchCommand cmd) = do
         hPutStrLn stderr $ "\"" ++ cmd ++ "\" not supported"
         printUsage