Add HsSyn prettyprinter tests

Summary:
Add prettyprinter tests, which take a file, parse it, pretty print it,
re-parse the pretty printed version and then compare the original and
new ASTs (ignoring locations)

Updates haddock submodule to match the AST changes.

There are three issues outstanding

1. Extra parens around a context are not reproduced. This will require an
   AST change and will be done in a separate patch.

2. Currently if an `HsTickPragma` is found, this is not pretty-printed,
   to prevent noise in the output.

   I am not sure what the desired behaviour in this case is, so have left
   it as before. Test Ppr047 is marked as expected fail for this.

3. Apart from in a context, the ParsedSource AST keeps all the parens from
   the original source.  Something is happening in the renamer to remove the
   parens around visible type application, causing T12530 to fail, as the
   dumped splice decl is after the renamer.

   This needs to be fixed by keeping the parens, but I do not know where they
   are being removed.  I have amended the test to pass, by removing the parens
   in the expected output.

Test Plan: ./validate

Reviewers: goldfire, mpickering, simonpj, bgamari, austin

Reviewed By: simonpj, bgamari

Subscribers: simonpj, goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D2752

GHC Trac Issues: #3384

4 files changed, 289 insertions, 0 deletions

diff --git a/utils/check-ppr/Main.hs b/utils/check-ppr/Main.hs
new file mode 100644
index 0000000000..c61b0e6d4c
--- /dev/null
+++ b/utils/check-ppr/Main.hs
@@ -0,0 +1,219 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE RankNTypes #-}
+
+import Data.Data hiding (Fixity)
+import Data.List
+import Bag
+import FastString
+import NameSet
+import SrcLoc
+import HsSyn
+import OccName hiding (occName)
+import GHC hiding (moduleName)
+import Var
+import DynFlags
+import Outputable hiding (space)
+import System.Environment( getArgs )
+import System.Exit
+import System.FilePath
+
+import qualified Data.ByteString as B
+import qualified Data.Map        as Map
+
+main::IO()
+main = do
+  args <- getArgs
+  case args of
+   [libdir,fileName] -> testOneFile libdir fileName
+   _ -> putStrLn "invoke with the libdir and a file to parse."
+
+testOneFile :: FilePath -> String -> IO ()
+testOneFile libdir fileName = do
+       p <- parseOneFile libdir fileName
+       let
+         origAst = showAstData 0 (pm_parsed_source p)
+         pped    = pragmas ++ "\n" ++ pp (pm_parsed_source p)
+         anns    = pm_annotations p
+         pragmas = getPragmas anns
+
+         newFile = dropExtension fileName <.> "ppr" <.> takeExtension fileName
+         astFile = fileName <.> "ast"
+
+       writeFile astFile origAst
+       writeFile newFile pped
+
+       p' <- parseOneFile libdir newFile
+
+       let newAstStr = showAstData 0 (pm_parsed_source p')
+
+       if origAst == newAstStr
+         then do
+           -- putStrLn "ASTs matched"
+           exitSuccess
+         else do
+           putStrLn "AST Match Failed"
+           putStrLn "\n===================================\nOrig\n\n"
+           putStrLn origAst
+           putStrLn "\n===================================\nNew\n\n"
+           putStrLn newAstStr
+           exitFailure
+
+
+parseOneFile :: FilePath -> FilePath -> IO ParsedModule
+parseOneFile libdir fileName = do
+       let modByFile m =
+             case ml_hs_file $ ms_location m of
+               Nothing -> False
+               Just fn -> fn == fileName
+       runGhc (Just libdir) $ do
+         dflags <- getSessionDynFlags
+         let dflags2 = dflags `gopt_set` Opt_KeepRawTokenStream
+         _ <- setSessionDynFlags dflags2
+         addTarget Target { targetId = TargetFile fileName Nothing
+                          , targetAllowObjCode = True
+                          , targetContents = Nothing }
+         _ <- load LoadAllTargets
+         graph <- getModuleGraph
+         let
+           modSum = case filter modByFile graph of
+                     [x] -> x
+                     xs -> error $ "Can't find module, got:"
+                              ++ show (map (ml_hs_file . ms_location) xs)
+         parseModule modSum
+
+getPragmas :: ApiAnns -> String
+getPragmas anns = pragmaStr
+  where
+    tokComment (L _ (AnnBlockComment s)) = s
+    tokComment (L _ (AnnLineComment  s)) = s
+    tokComment _ = ""
+
+    comments = case Map.lookup noSrcSpan (snd anns) of
+      Nothing -> []
+      Just cl -> map tokComment $ sortLocated cl
+    pragmas = filter (\c -> isPrefixOf "{-#" c ) comments
+    pragmaStr = intercalate "\n" pragmas
+
+pp :: (Outputable a) => a -> String
+pp a = showPpr unsafeGlobalDynFlags a
+
+
+-- | Show a GHC AST with SrcSpan's blanked out, to avoid comparing locations,
+-- only structure
+showAstData :: Data a => Int -> a -> String
+showAstData n =
+  generic
+          `ext1Q` list
+          `extQ` string `extQ` fastString `extQ` srcSpan
+          `extQ` bytestring
+          `extQ` name `extQ` occName `extQ` moduleName `extQ` var `extQ` dataCon
+          `extQ` bagName `extQ` bagRdrName `extQ` bagVar `extQ` nameSet
+          `extQ` fixity
+          `ext2Q` located
+  where generic :: Data a => a -> String
+        generic t = indent n ++ "(" ++ showConstr (toConstr t)
+                 ++ space (unwords (gmapQ (showAstData (n+1)) t)) ++ ")"
+        space "" = ""
+        space s  = ' ':s
+        indent i = "\n" ++ replicate i ' '
+        string     = show :: String -> String
+        fastString = ("{FastString: "++) . (++"}") . show
+                   :: FastString -> String
+        bytestring = show :: B.ByteString -> String
+        list l     = indent n ++ "["
+                              ++ intercalate "," (map (showAstData (n+1)) l)
+                              ++ "]"
+
+        name       = ("{Name: "++) . (++"}") . showSDocDebug_ . ppr
+                  :: Name -> String
+        occName    = ("{OccName: "++) . (++"}") .  OccName.occNameString
+        moduleName = ("{ModuleName: "++) . (++"}") . showSDoc_ . ppr
+                   :: ModuleName -> String
+
+        srcSpan :: SrcSpan -> String
+        srcSpan _ss = "{ "++ "ss" ++"}"
+
+        var        = ("{Var: "++) . (++"}") . showSDocDebug_ . ppr
+                   :: Var -> String
+        dataCon    = ("{DataCon: "++) . (++"}") . showSDoc_ . ppr
+                   :: DataCon -> String
+
+        bagRdrName:: Bag (Located (HsBind RdrName)) -> String
+        bagRdrName = ("{Bag(Located (HsBind RdrName)): "++) . (++"}")
+                      . list . bagToList
+        bagName   :: Bag (Located (HsBind Name)) -> String
+        bagName    = ("{Bag(Located (HsBind Name)): "++) . (++"}")
+                       . list . bagToList
+        bagVar    :: Bag (Located (HsBind Var)) -> String
+        bagVar     = ("{Bag(Located (HsBind Var)): "++) . (++"}")
+                       . list . bagToList
+
+        nameSet = ("{NameSet: "++) . (++"}") . list . nameSetElemsStable
+
+        fixity = ("{Fixity: "++) . (++"}") . showSDoc_ . ppr
+               :: Fixity -> String
+
+        located :: (Data b,Data loc) => GenLocated loc b -> String
+        located (L ss a) =
+          indent n ++ "("
+            ++ case cast ss of
+                    Just (s :: SrcSpan) ->
+                      srcSpan s
+                    Nothing -> "nnnnnnnn"
+                  ++ showAstData (n+1) a
+                  ++ ")"
+
+showSDoc_ :: SDoc -> String
+showSDoc_ = showSDoc unsafeGlobalDynFlags
+
+showSDocDebug_ :: SDoc -> String
+showSDocDebug_ = showSDocDebug unsafeGlobalDynFlags
+
+-- ---------------------------------------------------------------------
+
+-- Copied from syb for the test
+
+
+-- | The type constructor for queries
+newtype Q q x = Q { unQ :: x -> q }
+
+-- | Extend a generic query by a type-specific case
+extQ :: ( Typeable a
+        , Typeable b
+        )
+     => (a -> q)
+     -> (b -> q)
+     -> a
+     -> q
+extQ f g a = maybe (f a) g (cast a)
+
+-- | Type extension of queries for type constructors
+ext1Q :: (Data d, Typeable t)
+      => (d -> q)
+      -> (forall e. Data e => t e -> q)
+      -> d -> q
+ext1Q def ext = unQ ((Q def) `ext1` (Q ext))
+
+
+-- | Type extension of queries for type constructors
+ext2Q :: (Data d, Typeable t)
+      => (d -> q)
+      -> (forall d1 d2. (Data d1, Data d2) => t d1 d2 -> q)
+      -> d -> q
+ext2Q def ext = unQ ((Q def) `ext2` (Q ext))
+
+-- | Flexible type extension
+ext1 :: (Data a, Typeable t)
+     => c a
+     -> (forall d. Data d => c (t d))
+     -> c a
+ext1 def ext = maybe def id (dataCast1 ext)
+
+
+
+-- | Flexible type extension
+ext2 :: (Data a, Typeable t)
+     => c a
+     -> (forall d1 d2. (Data d1, Data d2) => c (t d1 d2))
+     -> c a
+ext2 def ext = maybe def id (dataCast2 ext)
diff --git a/utils/check-ppr/README b/utils/check-ppr/README
new file mode 100644
index 0000000000..ac0eb55977
--- /dev/null
+++ b/utils/check-ppr/README
@@ -0,0 +1,20 @@
+
+This programme is intended to be used by any GHC developers working on the AST
+and/or pretty printer by providing a way to check that the same AST is generated
+from the pretty printed AST as from the original source.
+
+i.e., it checks whether
+
+    parse (ppr (parse s)) === parse s
+
+
+This utility is also intended to be used in tests, so that when new features are
+added the ability to round-trip the AST via ppr is tested.
+
+Usage
+
+In a test Makefile
+
+  $(CHECK_PPR) "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`" FileToParse.hs
+
+See examples in (REPO_HOME)/testsuite/tests/printer/Makefile
diff --git a/utils/check-ppr/check-ppr.cabal b/utils/check-ppr/check-ppr.cabal
new file mode 100644
index 0000000000..96863e58fa
--- /dev/null
+++ b/utils/check-ppr/check-ppr.cabal
@@ -0,0 +1,32 @@
+Name: check-ppr
+Version: 0.1
+Copyright: XXX
+License: BSD3
+-- XXX License-File: LICENSE
+Author: XXX
+Maintainer: XXX
+Synopsis: A utilities for checking the consistency of GHC's pretty printer
+Description:
+    This utility is used to check the consistency of the GHC pretty printer, by
+    parsing a file, pretty printing it, and then re-parsing the pretty printed
+    version. See @utils/check-ppr/README@ in GHC's source distribution for
+    details.
+Category: Development
+build-type: Simple
+cabal-version: >=1.10
+
+Executable check-ppr
+    Default-Language: Haskell2010
+
+    Main-Is: Main.hs
+
+    Ghc-Options: -Wall
+
+    Build-Depends: base       >= 4   && < 5,
+                   bytestring,
+                   containers,
+                   -- Cabal      >= 1.25 && <1.27,
+                   Cabal      >= 1.24 && <1.27,
+                   directory,
+                   filepath,
+                   ghc
diff --git a/utils/check-ppr/ghc.mk b/utils/check-ppr/ghc.mk
new file mode 100644
index 0000000000..189b447171
--- /dev/null
+++ b/utils/check-ppr/ghc.mk
@@ -0,0 +1,18 @@
+# -----------------------------------------------------------------------------
+#
+# (c) 2009 The University of Glasgow
+#
+# This file is part of the GHC build system.
+#
+# To understand how the build system works and how to modify it, see
+#      http://ghc.haskell.org/trac/ghc/wiki/Building/Architecture
+#      http://ghc.haskell.org/trac/ghc/wiki/Building/Modifying
+#
+# -----------------------------------------------------------------------------
+
+utils/check-ppr_USES_CABAL                   = YES
+utils/check-ppr_PACKAGE                      = check-ppr
+utils/check-ppr_dist-install_PROGNAME        = check-ppr
+utils/check-ppr_dist-install_INSTALL         = NO
+utils/check-ppr_dist-install_INSTALL_INPLACE = YES
+$(eval $(call build-prog,utils/check-ppr,dist-install,2))