Move sandbox setup into initGhci

As it turns out, setSessionDynFlags calls initPackage. Unfortunately,
initPackage only reads the package database the first time it is called.
Therefore, we need to set extraPkgConfs before we call
setSessionDynFlags for the first time in order for the sandbox to be
used. Since initGhci is the first caller of setSessionDynFlags, we make
it responsible for this.

src/IHaskell/Eval/Evaluate.hs

@@ -119,18 +119,9 @@ globalImports =
 -- is handled specially, which cannot be done in a testing environment.
 interpret :: Bool -> Interpreter a -> IO a
 interpret allowedStdin action = runGhc (Just libdir) $ do
-  initGhci
-
   -- If we're in a sandbox, add the relevant package database
-  dflags <- getSessionDynFlags
   sandboxPackages <- liftIO getSandboxPackageConf
-  let pkgConfs = case sandboxPackages of
-        Nothing -> extraPkgConfs dflags
-        Just path ->
-          let pkg  = PkgConfFile path in
-            (pkg:) . extraPkgConfs dflags
-
-  void $ setSessionDynFlags $ dflags { extraPkgConfs = pkgConfs }
+  initGhci sandboxPackages
 
   initializeImports
 

src/IHaskell/Eval/Util.hs

@@ -131,18 +131,28 @@ doc sdoc = do
 -- @NoMonomorphismRestriction@), sets the target to interpreted, link in
 -- memory, sets a reasonable output width, and potentially a few other
 -- things. It should be invoked before other functions from this module.
-initGhci :: GhcMonad m => m ()
-initGhci = do
+--
+-- We also require that the sandbox PackageConf (if any) is passed here
+-- as setSessionDynFlags will read the package database the first time
+-- (and only the first time) it is called.
+initGhci :: GhcMonad m => Maybe String -> m ()
+initGhci sandboxPackages = do
   -- Initialize dyn flags.
   -- Start with -XExtendedDefaultRules and -XNoMonomorphismRestriction.
   originalFlags <- getSessionDynFlags
   let flag = flip xopt_set
       unflag = flip xopt_unset
       dflags = flag Opt_ExtendedDefaultRules . unflag Opt_MonomorphismRestriction $ originalFlags
+      pkgConfs = case sandboxPackages of
+        Nothing -> extraPkgConfs originalFlags
+        Just path ->
+          let pkg  = PkgConfFile path in
+            (pkg:) . extraPkgConfs originalFlags
 
   void $ setSessionDynFlags $ dflags { hscTarget = HscInterpreted,
                                        ghcLink = LinkInMemory,
-                                       pprCols = 300 }
+                                       pprCols = 300,
+                                       extraPkgConfs = pkgConfs }
 
 -- | Evaluate a single import statement.
 -- If this import statement is importing a module which was previously