Let Cabal determine the package-db stack

Language/Haskell/GhcMod/World.hs

@@ -3,6 +3,7 @@ module Language.Haskell.GhcMod.World where
 import Language.Haskell.GhcMod.GhcPkg
 import Language.Haskell.GhcMod.PathsAndFiles
 import Language.Haskell.GhcMod.Types
+import Language.Haskell.GhcMod.Monad.Types
 import Language.Haskell.GhcMod.Utils
 
 import Control.Applicative
@@ -20,18 +21,19 @@ data World = World {
   , worldSymbolCache   :: Maybe TimedFile
   } deriving (Eq, Show)
 
-timedPackageCaches :: Cradle -> IO [TimedFile]
-timedPackageCaches crdl = do
-    fs <- mapM mightExist . map (</> packageCache)
-            =<< getPackageCachePaths libdir crdl
-    timeFile `mapM` catMaybes fs
+timedPackageCaches :: IOish m => GhcModT m [TimedFile]
+timedPackageCaches = do
+    fs <- mapM (liftIO . mightExist) . map (</> packageCache)
+            =<< getPackageCachePaths libdir
+    (liftIO . timeFile) `mapM` catMaybes fs
 
-getCurrentWorld :: Cradle -> IO World
-getCurrentWorld crdl = do
-    pkgCaches    <- timedPackageCaches crdl
-    mCabalFile   <- timeFile `traverse` cradleCabalFile crdl
-    mCabalConfig <- timeMaybe (setupConfigFile crdl)
-    mSymbolCache <- timeMaybe (symbolCache crdl)
+getCurrentWorld :: IOish m => GhcModT m World
+getCurrentWorld = do
+    crdl <- cradle
+    pkgCaches    <- timedPackageCaches
+    mCabalFile   <- liftIO $ timeFile `traverse` cradleCabalFile crdl
+    mCabalConfig <- liftIO $ timeMaybe (setupConfigFile crdl)
+    mSymbolCache <- liftIO $ timeMaybe (symbolCache crdl)
 
     return World {
         worldPackageCaches = pkgCaches
@@ -40,26 +42,9 @@ getCurrentWorld crdl = do
       , worldSymbolCache   = mSymbolCache
       }
 
-didWorldChange :: World -> Cradle -> IO Bool
-didWorldChange world crdl = do
-    (world /=) <$> getCurrentWorld crdl
-
--- * Neither file exists -> should return False:
---   @Nothing < Nothing = False@
---   (since we don't need to @cabal configure@ when no cabal file exists.)
---
--- * Cabal file doesn't exist (unlikely case) -> should return False
---   @Just cc < Nothing = False@
---   TODO: should we delete dist/setup-config?
---
--- * dist/setup-config doesn't exist yet -> should return True:
---   @Nothing < Just cf = True@
---
--- * Both files exist
---   @Just cc < Just cf = cc < cf = cc `olderThan` cf@
-isSetupConfigOutOfDate :: World -> Bool
-isSetupConfigOutOfDate World {..} = do
-  worldCabalConfig < worldCabalFile
+didWorldChange :: IOish m => World -> GhcModT m Bool
+didWorldChange world = do
+    (world /=) <$> getCurrentWorld
 
 isYoungerThanSetupConfig :: FilePath -> World -> IO Bool
 isYoungerThanSetupConfig file World {..} = do