Expand response files in arguments

Closes #285

1 files changed, 25 insertions, 3 deletions

diff --git a/driver/Main.hs b/driver/Main.hs
index 42b99860..5097a86d 100644
--- a/driver/Main.hs
+++ b/driver/Main.hs
@@ -1,7 +1,29 @@
+{-# LANGUAGE ScopedTypeVariables #-}
 module Main where
 
-import           Documentation.Haddock (haddock)
-import           System.Environment (getArgs)
+import Control.Exception
+import Documentation.Haddock (haddock)
+import System.Environment (getArgs)
+import System.Exit (exitFailure)
+import System.IO
 
 main :: IO ()
-main = getArgs >>= haddock
+main = getArgs >>= expandResponse >>= haddock
+
+
+-- | Arguments which look like '@foo' will be replaced with the
+-- contents of file @foo@. The contents will be passed through 'words'
+-- and blanks filtered out first.
+--
+-- We quit if the file is not found or reading somehow fails.
+expandResponse :: [String] -> IO [String]
+expandResponse = fmap concat . mapM expand
+  where
+    expand :: String -> IO [String]
+    expand ('@':f) = readFileExc f >>= return . filter (not . null) . words
+    expand x = return [x]
+
+    readFileExc f =
+      readFile f `catch` \(e :: IOException) -> do
+        hPutStrLn stderr $ "Error while expanding response file: " ++ show e
+        exitFailure