Recache cabal-helper stuff when cabal-helper-* executable changes

Language/Haskell/GhcMod/CabalHelper.hs

@@ -80,18 +80,17 @@ data CabalHelper = CabalHelper {
 
 cabalHelper :: (MonadIO m, GmEnv m) => m CabalHelper
 cabalHelper = withCabal $ do
+  Cradle {..} <- cradle
   let cmds = [ "entrypoints"
              , "source-dirs"
              , "ghc-options"
              , "ghc-src-options"
              , "ghc-pkg-options" ]
+      distdir = cradleRootDir </> "dist"
 
-  Cradle {..} <- cradle
   exe <- liftIO $ findLibexecExe "cabal-helper-wrapper"
-
-  let distdir = cradleRootDir </> "dist"
-
-  res <- liftIO $ cached cradleRootDir (cabalHelperCache cmds) $ do
+  hexe <- liftIO $ readProcess exe [distdir, "print-exe"] ""
+  res <- liftIO $ cached cradleRootDir (cabalHelperCache hexe cmds) $ do
            out <- readProcess exe (distdir:cmds) ""
            evaluate (read out) `E.catch`
                \(SomeException _) -> error "cabalHelper: read failed"

Language/Haskell/GhcMod/PathsAndFiles.hs

@@ -233,9 +233,10 @@ cabalBuildPlatform = dropWhileEnd isSpace $ unsafePerformIO $
 packageCache :: String
 packageCache = "package.cache"
 
-cabalHelperCache :: [String] -> Cached [String] [Maybe GmCabalHelperResponse]
-cabalHelperCache cmds = Cached {
-    inputFiles = [setupConfigPath],
+cabalHelperCache ::
+    FilePath -> [String] -> Cached [String] [Maybe GmCabalHelperResponse]
+cabalHelperCache cabalHelperExe cmds = Cached {
+    inputFiles = [cabalHelperExe, setupConfigPath],
     inputData  = cmds,
     cacheFile  = setupConfigPath <.> "ghc-mod.cabal-helper"
   }