restore default options injection

yesod-bin/Options.hs

@@ -7,6 +7,8 @@ module Options (injectDefaults) where
 import           Control.Applicative
 import qualified Control.Exception         as E
 import           Control.Monad
+import           Control.Monad.Trans.Except
+import           Control.Monad.Trans.Reader
 import           Data.Char                 (isAlphaNum, isSpace, toLower)
 import           Data.List                 (foldl')
 import           Data.List.Split           (splitOn)
@@ -62,8 +64,6 @@ configLines = mapMaybe (mkLine . takeWhile (/='#')) . lines
 --   the map contains the paths with the value that's passed into the reader if the
 --   command line parser gives no result
 injectDefaultP :: M.Map [String] String -> [String] -> Parser a -> Parser a
-injectDefaultP _ _ = id
-{- FIXME Disabled due to changes in optparse-applicative 0.11
 injectDefaultP _env _path n@(NilP{})   = n
 injectDefaultP env path p@(OptP o)
   | (Option (CmdReader cmds f) props) <- o  =
@@ -73,20 +73,21 @@ injectDefaultP env path p@(OptP o)
            in  parseri { infoParser = injectDefaultP env (path ++ [normalizeName cmd]) (infoParser parseri) }
      in  OptP (Option (CmdReader cmds (`M.lookup` cmdMap)) props)
   | (Option (OptReader names (CReader _ rdr) _) _) <- o =
-     p <|> either' (const empty) pure (msum $ map (rdr <=< (maybe (left $ ErrorMsg "Missing environment variable") right . getEnvValue env path)) names)
+     p <|> either (const empty)
+                  pure
+                  (runExcept . msum $
+                    map (maybe (throwE $ ErrorMsg "Missing environment variable")
+                               (runReaderT (unReadM rdr))
+                          . getEnvValue env path)
+                        names)
   | (Option (FlagReader names a) _) <- o =
      p <|> if any ((==Just "1") . getEnvValue env path) names then pure a else empty
   | otherwise = p
-  where
-    right= ReadM . Right
-    left = ReadM . Left
-    either' f g (ReadM x) = either f g x
 injectDefaultP env path (MultP p1 p2) =
    MultP (injectDefaultP env path p1) (injectDefaultP env path p2)
 injectDefaultP env path (AltP p1 p2) =
    AltP (injectDefaultP env path p1) (injectDefaultP env path p2)
 injectDefaultP _env _path b@(BindP {}) = b
--}
 
 getEnvValue :: M.Map [String] String -> [String] -> OptName -> Maybe String
 getEnvValue env path (OptLong l) = M.lookup (path ++ [normalizeName l]) env

yesod-bin/yesod-bin.cabal

@@ -84,6 +84,7 @@ executable             yesod
                      , http-conduit       >= 2.1.4
                      , project-template   >= 0.1.1
                      , transformers
+                     , transformers-compat
                      , warp               >= 1.3.7.5
                      , wai                >= 1.4
                      , wai-extra