Have "stack ghci" only use "-package base" if there are no local targets

Author: mgsloan

ChangeLog.md

@@ -66,8 +66,12 @@ Bug fixes:
   associated with the relevant custom snapshot. See
   [#3714](https://github.com/commercialhaskell/stack/issues/3714).
 * `stack ghci` now allows loading multiple packages with the same
-  module name, as long as they are the same filepath. See
+  module name, as long as they have the same filepath. See
   [#3776](https://github.com/commercialhaskell/stack/pull/3776).
+* `stack ghci` no longer always adds a dependency on `base`. It is
+  now only added when there are no local targets. This allows it to
+  be to load code that uses replacements for `base`. See
+  [#3589](https://github.com/commercialhaskell/stack/issues/3589#issuecomment)
 
 ## v1.6.3
 

src/Stack/Ghci.hs

@@ -331,12 +331,13 @@ runGhci GhciOpts{..} targets mainIsTargets pkgs extraFiles exposePackages = do
           fromMaybe (not (null pkgs && null exposePackages)) ghciHidePackages
         hidePkgOpts =
           if shouldHidePackages
-            then "-hide-all-packages" :
+            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" :
+              (if null targets then ["-package", "base"] else []) ++
               concatMap (\n -> ["-package", packageNameString n]) exposePackages
             else []
         oneWordOpts bio