Use cabal-helper to support Cabal >= 1.22 with any version of ghc

Language/Haskell/GhcMod/Error.hs

@@ -1,6 +1,8 @@
 {-# LANGUAGE TypeFamilies, ScopedTypeVariables, DeriveDataTypeable #-}
 module Language.Haskell.GhcMod.Error (
     GhcModError(..)
+  , GMConfigStateFileError(..)
+  , GmError
   , gmeDoc
   , modifyError
   , modifyError'
@@ -15,26 +17,81 @@ import Data.Typeable
 import Exception
 import Text.PrettyPrint
 
+type GmError m = MonadError GhcModError m
+
 data GhcModError = GMENoMsg
                  -- ^ Unknown error
+
                  | GMEString String
                  -- ^ Some Error with a message. These are produced mostly by
                  -- 'fail' calls on GhcModT.
+
                  | GMEIOException IOException
                  -- ^ IOExceptions captured by GhcModT's MonadIO instance
+
                  | GMECabalConfigure GhcModError
                  -- ^ Configuring a cabal project failed.
+
                  | GMECabalFlags GhcModError
                  -- ^ Retrieval of the cabal configuration flags failed.
+
                  | GMEProcess [String] GhcModError
                  -- ^ Launching an operating system process failed. The first
                  -- field is the command.
+
                  | GMENoCabalFile
                  -- ^ No cabal file found.
+
                  | GMETooManyCabalFiles [FilePath]
                  -- ^ Too many cabal files found.
+
+                 | GMECabalStateFile GMConfigStateFileError
+                 -- ^ Reading Cabal's state configuration file falied somehow.
                    deriving (Eq,Show,Typeable)
 
+data GMConfigStateFileError
+    = GMConfigStateFileNoHeader
+    | GMConfigStateFileBadHeader
+    | GMConfigStateFileNoParse
+    | GMConfigStateFileMissing
+--    | GMConfigStateFileBadVersion PackageIdentifier PackageIdentifier (Either ConfigStateFileError LocalBuildInfo)
+  deriving (Eq, Show, Read, Typeable)
+
+gmCsfeDoc :: GMConfigStateFileError -> Doc
+gmCsfeDoc GMConfigStateFileNoHeader = text $
+        "Saved package config file header is missing. "
+        ++ "Try re-running the 'configure' command."
+
+gmCsfeDoc GMConfigStateFileBadHeader = text $
+        "Saved package config file header is corrupt. "
+        ++ "Try re-running the 'configure' command."
+
+gmCsfeDoc GMConfigStateFileNoParse = text $
+        "Saved package config file body is corrupt. "
+        ++ "Try re-running the 'configure' command."
+
+gmCsfeDoc GMConfigStateFileMissing = text $
+    "Run the 'configure' command first."
+
+-- gmCsfeDoc (ConfigStateFileBadVersion oldCabal oldCompiler _) = text $
+--         "You need to re-run the 'configure' command. "
+--         ++ "The version of Cabal being used has changed (was "
+--         ++ display oldCabal ++ ", now "
+--         ++ display currentCabalId ++ ")."
+--         ++ badCompiler
+--       where
+--         badCompiler
+--           | oldCompiler == currentCompilerId = ""
+--           | otherwise =
+--               " Additionally the compiler is different (was "
+--               ++ display oldCompiler ++ ", now "
+--               ++ display currentCompilerId
+--               ++ ") which is probably the cause of the problem."
+
+
+
+
+
 instance Exception GhcModError
 
 instance Error GhcModError where
@@ -61,6 +118,9 @@ gmeDoc e = case e of
     GMETooManyCabalFiles cfs ->
         text $ "Multiple cabal files found. Possible cabal files: \""
                ++ intercalate "\", \"" cfs ++"\"."
+    GMECabalStateFile csfe ->
+        gmCsfeDoc csfe
+
 
 modifyError :: MonadError e m => (e -> e) -> m a -> m a
 modifyError f action = action `catchError` \e -> throwError $ f e