Frontend plugins.

Summary:
Frontend plugins enable users to write plugins to replace
GHC major modes.  E.g. instead of saying

    ghc --make A B C

a user can now say

    ghc --frontend GHC.Frontend.Shake A B C

which might provide an alternative implementation of a multi-module
build.  For more details, see the manual entry.

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

Test Plan: validate

Reviewers: simonmar, bgamari, austin, simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1598

GHC Trac Issues: #11194

5 files changed, 67 insertions, 0 deletions

diff --git a/testsuite/tests/plugins/FrontendPlugin.hs b/testsuite/tests/plugins/FrontendPlugin.hs
new file mode 100644
index 0000000000..9a6c5d0514
--- /dev/null
+++ b/testsuite/tests/plugins/FrontendPlugin.hs
@@ -0,0 +1,52 @@
+module FrontendPlugin where
+
+import GhcPlugins
+import qualified GHC
+import GHC              ( Ghc, LoadHowMuch(..) )
+
+import DriverPipeline hiding ( hsc_env )
+import DriverPhases
+import System.Exit
+import Control.Monad
+import Data.List
+
+frontendPlugin :: FrontendPlugin
+frontendPlugin = defaultFrontendPlugin {
+        frontend = doMake
+    }
+
+-- Copypasted from ghc/Main.hs
+doMake :: [String] -> [(String,Maybe Phase)] -> Ghc ()
+doMake opts srcs  = do
+    liftIO $ print opts
+    let (hs_srcs, non_hs_srcs) = partition haskellish srcs
+
+        haskellish (f,Nothing) =
+          looksLikeModuleName f || isHaskellUserSrcFilename f || '.' `notElem` f
+        haskellish (_,Just phase) =
+          phase `notElem` [ As True, As False, Cc, Cobjc, Cobjcxx, CmmCpp, Cmm
+                          , StopLn]
+
+    hsc_env <- GHC.getSession
+
+    -- if we have no haskell sources from which to do a dependency
+    -- analysis, then just do one-shot compilation and/or linking.
+    -- This means that "ghc Foo.o Bar.o -o baz" links the program as
+    -- we expect.
+    if (null hs_srcs)
+       then liftIO (oneShot hsc_env StopLn srcs)
+       else do
+
+    o_files <- mapM (\x -> liftIO $ compileFile hsc_env StopLn x)
+                 non_hs_srcs
+    dflags <- GHC.getSessionDynFlags
+    let dflags' = dflags { ldInputs = map (FileOption "") o_files
+                                      ++ ldInputs dflags }
+    _ <- GHC.setSessionDynFlags dflags'
+
+    targets <- mapM (uncurry GHC.guessTarget) hs_srcs
+    GHC.setTargets targets
+    ok_flag <- GHC.load LoadAllTargets
+
+    when (failed ok_flag) (liftIO $ exitWith (ExitFailure 1))
+    return ()
diff --git a/testsuite/tests/plugins/Makefile b/testsuite/tests/plugins/Makefile
index 42a4d1af0a..c12c33c9c7 100644
--- a/testsuite/tests/plugins/Makefile
+++ b/testsuite/tests/plugins/Makefile
@@ -24,3 +24,10 @@ T10294:
 .PHONY: T10294a
 T10294a:
 	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -c -v0 T10294a.hs -package-db annotation-plugin/pkg.T10294a/local.package.conf -package annotation-plugin -fplugin=SayAnnNames
+
+.PHONY: frontend01
+frontend01:
+	$(RM) FrontendPlugin.hi FrontendPlugin.o frontend01 frontend01.hi frontend.o
+	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -Wall -package ghc -c FrontendPlugin.hs
+	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) --frontend FrontendPlugin -ffrontend-opt foobar frontend01
+	./frontend01
diff --git a/testsuite/tests/plugins/all.T b/testsuite/tests/plugins/all.T
index bc3bcfa2dd..2e4aacf29c 100644
--- a/testsuite/tests/plugins/all.T
+++ b/testsuite/tests/plugins/all.T
@@ -62,3 +62,6 @@ test('T10294a',
       clean_cmd('$MAKE -s --no-print-directory -C annotation-plugin clean.T10294a')],
      run_command,
      ['$MAKE -s --no-print-directory T10294a'])
+
+test('frontend01', [ extra_clean(['FrontendPlugin.hi', 'FrontendPlugin.o', 'frontend01', 'frontend01.o', 'frontend01.hi']) ],
+     run_command, ['$MAKE -s --no-print-directory frontend01'])
diff --git a/testsuite/tests/plugins/frontend01.hs b/testsuite/tests/plugins/frontend01.hs
new file mode 100644
index 0000000000..db014568d4
--- /dev/null
+++ b/testsuite/tests/plugins/frontend01.hs
@@ -0,0 +1 @@
+main = putStrLn "hello world"
diff --git a/testsuite/tests/plugins/frontend01.stdout b/testsuite/tests/plugins/frontend01.stdout
new file mode 100644
index 0000000000..84950bcbc9
--- /dev/null
+++ b/testsuite/tests/plugins/frontend01.stdout
@@ -0,0 +1,4 @@
+["foobar"]
+[1 of 1] Compiling Main             ( frontend01.hs, frontend01.o )
+Linking frontend01 ...
+hello world