Implement -hide-all-plugin-packages and -plugin-package(-id), fixing #11244

Summary:
The basic idea is that we have a new set of "exposed modules"
which are /only/ used for plugins, i.e. -fplugin Foo and
--frontend Foo.  You can interact with this namespace
using the flags -plugin-package-id and -plugin-package.
By default, this namespace contains all modules in the
user namespace (as before), but you can toggle that using
-hide-all-plugin-packages.

There is one nasty hack: GhcMake respects -fplugin in
GHC_OPTIONS to make local plugins work correctly.  It also
bails out of you have an import of a module which doesn't
exist locally or in the package database.  The upshot is
that we need to be sure to check in the plugin modules
too, so we don't give a spurious failure when a plugin
is in the plugin namespace but not the main namespace.
A better way to fix this would be to distinguish between
plugin and normal dependencies in ModSummary.

I cheated a little and tweaked a few existing plugins
tests to exercise the new code paths.

TODO: Documentation

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: bgamari, austin, simonpj, duncan

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1661

GHC Trac Issues: #11244

1 files changed, 9 insertions, 3 deletions

diff --git a/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index 986c119783..4fcbe6d7fe 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -2377,6 +2377,13 @@ setOptions wds =
       -- then, dynamic flags
       newDynFlags False minus_opts
 
+packageFlagsChanged :: DynFlags -> DynFlags -> Bool
+packageFlagsChanged idflags1 idflags0 =
+    packageFlags idflags1 /= packageFlags idflags0 ||
+    ignorePackageFlags idflags1 /= ignorePackageFlags idflags0 ||
+    pluginPackageFlags idflags1 /= pluginPackageFlags idflags0 ||
+    trustFlags idflags1 /= trustFlags idflags0
+
 newDynFlags :: Bool -> [String] -> GHCi ()
 newDynFlags interactive_only minus_opts = do
       let lopts = map noLoc minus_opts
@@ -2390,8 +2397,7 @@ newDynFlags interactive_only minus_opts = do
             $ "Some flags have not been recognized: "
             ++ (concat . intersperse ", " $ map unLoc leftovers))
 
-      when (interactive_only &&
-              packageFlags idflags1 /= packageFlags idflags0) $ do
+      when (interactive_only && packageFlagsChanged idflags1 idflags0) $ do
           liftIO $ hPutStrLn stderr "cannot set package flags with :seti; use :set"
       GHC.setInteractiveDynFlags idflags1
       installInteractivePrint (interactivePrint idflags1) False
@@ -2405,7 +2411,7 @@ newDynFlags interactive_only minus_opts = do
         -- the new packages.
         hsc_env <- GHC.getSession
         let dflags2 = hsc_dflags hsc_env
-        when (packageFlags dflags2 /= packageFlags dflags0) $ do
+        when (packageFlagsChanged dflags2 dflags0) $ do
           when (verbosity dflags2 > 0) $
             liftIO . putStrLn $
               "package flags have changed, resetting and loading new packages..."