Refactoring to use cabal-helper-wrapper

This turned out to be quite involved but save for this huge commit it's
actually quite awesome and squashes quite a few bugs and nasty
problems (hopefully). Most importantly we now have native cabal
component support without the user having to do anything to get it!

To do this we traverse imports starting from each component's
entrypoints (library modules or Main source file for executables) and
use this information to find which component's options each module will
build with. Under the assumption that these modules have to build with
every component they're used in we can now just pick one.

Quite a few internal assumptions have been invalidated by this
change. Most importantly the runGhcModT* family of cuntions now change
the current working directory to `cradleRootDir`.

Language/Haskell/GhcMod/Logging.hs

@@ -1,4 +1,3 @@
-module Language.Haskell.GhcMod.Logging where
 -- ghc-mod: Making Haskell development *more* fun
 -- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
 --
@@ -15,22 +14,45 @@ module Language.Haskell.GhcMod.Logging where
 -- You should have received a copy of the GNU Affero General Public License
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-import Language.Haskell.GhcMod.Types
-import Language.Haskell.GhcMod.Monad.Types
+module Language.Haskell.GhcMod.Logging (
+    module Language.Haskell.GhcMod.Logging
+  , module Language.Haskell.GhcMod.Pretty
+  , GmLogLevel(..)
+  , module Text.PrettyPrint
+  , module Data.Monoid
+  ) where
 
-import Control.Monad.Journal.Class
-import Control.Monad.Trans.Class
+import Control.Monad
+import Data.Monoid (mempty, mappend, mconcat, (<>))
 import System.IO
+import Text.PrettyPrint hiding (style, (<>))
 
-import MonadUtils
+import Language.Haskell.GhcMod.Monad.Types
+import Language.Haskell.GhcMod.Pretty
 
---gmSink :: IOish m => (GhcModLog -> IO ()) -> GhcModT m ()
---gmSink = GhcModT . (lift . lift . sink)
+gmSetLogLevel :: GmLog m => GmLogLevel -> m ()
+gmSetLogLevel level =
+    gmlJournal $ GhcModLog (Just level) []
 
-type GmLog m = MonadJournal GhcModLog m
+increaseLogLevel :: GmLogLevel -> GmLogLevel
+increaseLogLevel l | l == maxBound = l
+increaseLogLevel l = succ l
 
-gmJournal :: IOish m => GhcModLog -> GhcModT m ()
-gmJournal = GhcModT . lift . lift . journal
+-- |
+-- >>> Just GmDebug <= Nothing
+-- False
+-- >>> Just GmException <= Just GmDebug
+-- True
+-- >>> Just GmDebug <= Just GmException
+-- False
+gmLog :: (MonadIO m, GmLog m) => GmLogLevel -> String -> Doc -> m ()
+gmLog level loc' doc = do
+  GhcModLog { gmLogLevel = level' } <- gmlHistory
 
-gmLog :: (MonadIO m, MonadJournal GhcModLog m) => String -> m ()
-gmLog str = liftIO (hPutStrLn stderr str) >> (journal $ GhcModLog [str])
+  let loc | loc' == "" = empty
+          | otherwise = text (head $ lines loc') <> colon
+      msg = gmRenderDoc $ gmLogLevelDoc level <+> loc <+> doc
+
+  when (Just level <= level') $
+       liftIO $ hPutStrLn stderr msg
+  gmlJournal (GhcModLog Nothing [(level, render loc, msg)])