Add an option to customize the typed holes settings

Refinement hole fits are very cool, but currently too slow to enable at deeper
levels. It should eventually be user configurable.

session-loader/Development/IDE/Session.hs

@@ -105,7 +105,10 @@ loadSession dir = do
     ShakeExtras{logger, eventer, restartShakeSession, withIndefiniteProgress
                ,ideNc, knownFilesVar, session=ideSession} <- getShakeExtras
 
-    IdeOptions{optTesting = IdeTesting optTesting, optCheckProject = CheckProject checkProject } <- getIdeOptions
+    IdeOptions{ optTesting = IdeTesting optTesting
+              , optCheckProject = CheckProject checkProject
+              , optCustomDynFlags
+              } <- getIdeOptions
 
     -- Create a new HscEnv from a hieYaml root and a set of options
     -- If the hieYaml file already has an HscEnv, the new component is
@@ -117,7 +120,7 @@ loadSession dir = do
           -- Parse DynFlags for the newly discovered component
           hscEnv <- emptyHscEnv ideNc libDir
           (df, targets) <- evalGhcEnv hscEnv $
-              setOptions opts (hsc_dflags hscEnv)
+              first optCustomDynFlags <$> setOptions opts (hsc_dflags hscEnv)
           let deps = componentDependencies opts ++ maybeToList hieYaml
           dep_info <- getDependencyInfo deps
           -- Now lookup to see whether we are combining with an existing HscEnv

src/Development/IDE/Types/Options.hs

@@ -94,6 +94,9 @@ data IdeOptions = IdeOptions
     --   Otherwise, return the result of parsing without Opt_Haddock, so
     --   that the parsed module contains the result of Opt_KeepRawTokenStream,
     --   which might be necessary for hlint.
+  , optCustomDynFlags :: DynFlags -> DynFlags
+    -- ^ If given, it will be called right after setting up a new cradle,
+    --   allowing to customize the Ghc options used
   }
 
 data OptHaddockParse = HaddockParse | NoHaddockParse
@@ -157,6 +160,7 @@ defaultIdeOptions session = IdeOptions
     ,optCheckProject = checkProject defaultLspConfig
     ,optCheckParents = checkParents defaultLspConfig
     ,optHaddockParse = HaddockParse
+    ,optCustomDynFlags = id
     }