Fix package-hiding option parsing + always expose base to ghci

Author: mgsloan

src/Stack/Ghci.hs

@@ -323,7 +323,13 @@ runGhci GhciOpts{..} targets mainIsTargets pkgs extraFiles exposePackages = do
           fromMaybe (not (null pkgs && null exposePackages)) ghciHidePackages
         hidePkgOpts =
           if shouldHidePackages
-            then "-hide-all-packages" : concatMap (\n -> ["-package", packageNameString n]) exposePackages
+            then "-hide-all-packages" :
+              -- This is necessary, because current versions of ghci
+              -- will entirely fail to start if base isn't visible. This
+              -- is because it tries to use the interpreter to set
+              -- buffering options on standard IO.
+              "-package" : "base" :
+              concatMap (\n -> ["-package", packageNameString n]) exposePackages
             else []
         oneWordOpts bio
             | shouldHidePackages = bioOneWordOpts bio ++ bioPackageFlags bio

src/Stack/Options/GhciParser.hs

@@ -52,6 +52,6 @@ ghciOptsParser = GhciOpts
              <*> switch (long "load-local-deps" <> help "Load all local dependencies of your targets")
              -- TODO: deprecate this? probably useless.
              <*> switch (long "skip-intermediate-deps" <> help "Skip loading intermediate target dependencies" <> internal)
-             <*> optional (boolFlags True "package-hiding" "package hiding" idm)
+             <*> optional (boolFlagsNoDefault "package-hiding" "package hiding" idm)
              <*> switch (long "no-build" <> help "Don't build before launching GHCi" <> internal)
              <*> switch (long "only-main" <> help "Only load and import the main module.  If no main module, no modules will be loaded.")