Modify flag parser to allow sequential dashes #3345

Author: snoyberg

ChangeLog.md

@@ -82,6 +82,9 @@ Bug fixes:
   mismatched hashes), Stack will delete the downloaded file and
   recommend either retrying or filing an issue upstream. See
   [#3319](https://github.com/commercialhaskell/stack/issues/3319).
+* Modified the flag parser within Stack to match the behavior of
+  Cabal's flag parser, which allows multiple sequential dashes. See
+  [#3345](https://github.com/commercialhaskell/stack/issues/3345)
 
 
 ## 1.5.1

src/Stack/Types/FlagName.hs

@@ -24,8 +24,7 @@ module Stack.Types.FlagName
 
 import           Stack.Prelude
 import           Data.Aeson.Extended
-import           Data.Attoparsec.Combinators
-import           Data.Attoparsec.Text
+import           Data.Attoparsec.Text as A
 import           Data.Char (isLetter, isDigit, toLower)
 import qualified Data.Text as T
 import qualified Distribution.PackageDescription as Cabal
@@ -72,13 +71,10 @@ instance FromJSONKey FlagName where
 
 -- | Attoparsec parser for a flag name
 flagNameParser :: Parser FlagName
-flagNameParser =
-  fmap (FlagName . T.pack)
-       (appending (many1 (satisfy isLetter))
-                  (concating (many (alternating
-                                      (pured (satisfy isAlphaNum))
-                                      (appending (pured (satisfy separator))
-                                                 (pured (satisfy isAlphaNum)))))))
+flagNameParser = fmap FlagName $ do
+  t <- A.takeWhile1 (\c -> isAlphaNum c || separator c)
+  when (T.head t == '-') $ fail "flag name cannot start with dash"
+  return t
   where separator c = c == '-' || c == '_'
         isAlphaNum c = isLetter c || isDigit c