Merge remote-tracking branch 'randen/bug468'

2 files changed, 111 insertions, 22 deletions

diff --git a/driver/Main.hs b/driver/Main.hs
index ccbb8b7d..852f44c7 100644
--- a/driver/Main.hs
+++ b/driver/Main.hs
@@ -1,29 +1,8 @@
-{-# LANGUAGE ScopedTypeVariables #-}
 module Main where
 
-import Control.Exception
 import Documentation.Haddock (haddock)
+import ResponseFile (expandResponse)
 import System.Environment (getArgs)
-import System.Exit (exitFailure)
-import System.IO
 
 main :: IO ()
 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) . lines
-    expand x = return [x]
-
-    readFileExc f =
-      readFile f `catch` \(e :: IOException) -> do
-        hPutStrLn stderr $ "Error while expanding response file: " ++ show e
-        exitFailure
diff --git a/driver/ResponseFile.hs b/driver/ResponseFile.hs
new file mode 100644
index 00000000..253c6004
--- /dev/null
+++ b/driver/ResponseFile.hs
@@ -0,0 +1,110 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+module ResponseFile (
+    unescapeArgs,
+    escapeArgs,
+    expandResponse
+  ) where
+
+import Control.Exception
+import Data.Char (isSpace)
+import Data.Foldable (foldl')
+import System.Exit (exitFailure)
+import System.IO
+
+
+-- | Given a string of concatenated strings, separate each by removing
+-- a layer of /quoting/ and\/or /escaping/ of certain characters.
+--
+-- These characters are: any whitespace, single quote, double quote,
+-- and the backslash character.  The backslash character always
+-- escapes (i.e., passes through without further consideration) the
+-- character which follows.  Characters can also be escaped in blocks
+-- by quoting (i.e., surrounding the blocks with matching pairs of
+-- either single- or double-quotes which are not themselves escaped).
+--
+-- Any whitespace which appears outside of either of the quoting and
+-- escaping mechanisms, is interpreted as having been added by this
+-- special concatenation process to designate where the boundaries
+-- are between the original, un-concatenated list of strings.  These
+-- added whitespace characters are removed from the output.
+--
+-- > unescapeArgs "hello\\ \\\"world\\\"\n" == escapeArgs "hello \"world\""
+unescapeArgs :: String -> [String]
+unescapeArgs = filter (not . null) . unescape
+
+-- | Given a list of strings, concatenate them into a single string
+-- with escaping of certain characters, and the addition of a newline
+-- between each string.  The escaping is done by adding a single
+-- backslash character before any whitespace, single quote, double
+-- quote, or backslash character, so this escaping character must be
+-- removed.  Unescaped whitespace (in this case, newline) is part
+-- of this "transport" format to indicate the end of the previous
+-- string and the start of a new string.
+--
+-- While 'unescapeArgs' allows using quoting (i.e., convenient
+-- escaping of many characters) by having matching sets of single- or
+-- double-quotes,'escapeArgs' does not use the quoting mechasnism,
+-- and thus will always escape any whitespace, quotes, and
+-- backslashes.
+--
+-- > unescapeArgs "hello\\ \\\"world\\\"\\n" == escapeArgs "hello \"world\""
+escapeArgs :: [String] -> String
+escapeArgs = unlines . map escapeArg
+
+-- | Arguments which look like '@foo' will be replaced with the
+-- contents of file @foo@. A gcc-like syntax for response files arguments
+-- is expected.  This must re-constitute the argument list by doing an
+-- inverse of the escaping mechanism done by the calling-program side.
+--
+-- We quit if the file is not found or reading somehow fails.
+-- (A convenience routine for haddock or possibly other clients)
+expandResponse :: [String] -> IO [String]
+expandResponse = fmap concat . mapM expand
+  where
+    expand :: String -> IO [String]
+    expand ('@':f) = readFileExc f >>= return . unescapeArgs
+    expand x = return [x]
+
+    readFileExc f =
+      readFile f `catch` \(e :: IOException) -> do
+        hPutStrLn stderr $ "Error while expanding response file: " ++ show e
+        exitFailure
+
+data Quoting = NoneQ | SngQ | DblQ
+
+unescape :: String -> [String]
+unescape args = reverse . map reverse $ go args NoneQ False [] []
+    where
+      -- n.b., the order of these cases matters; these are cribbed from gcc
+      -- case 1: end of input
+      go []     _q    _bs   a as = a:as
+      -- case 2: back-slash escape in progress
+      go (c:cs) q     True  a as = go cs q     False (c:a) as
+      -- case 3: no back-slash escape in progress, but got a back-slash
+      go (c:cs) q     False a as
+        | '\\' == c              = go cs q     True  a     as
+      -- case 4: single-quote escaping in progress
+      go (c:cs) SngQ  False a as
+        | '\'' == c              = go cs NoneQ False a     as
+        | otherwise              = go cs SngQ  False (c:a) as
+      -- case 5: double-quote escaping in progress
+      go (c:cs) DblQ  False a as
+        | '"' == c               = go cs NoneQ False a     as
+        | otherwise              = go cs DblQ  False (c:a) as
+      -- case 6: no escaping is in progress
+      go (c:cs) NoneQ False a as
+        | isSpace c              = go cs NoneQ False []    (a:as)
+        | '\'' == c              = go cs SngQ  False a     as
+        | '"'  == c              = go cs DblQ  False a     as
+        | otherwise              = go cs NoneQ False (c:a) as
+
+escapeArg :: String -> String
+escapeArg = reverse . foldl' escape []
+
+escape :: String -> Char -> String
+escape cs c
+  |    isSpace c
+    || '\\' == c
+    || '\'' == c
+    || '"'  == c = c:'\\':cs -- n.b., our caller must reverse the result
+  | otherwise    = c:cs