Allow the parser to spit out meta-info

Currently we only use it only for ‘since’ annotations but with these
patches it should be fairly simple to add new attributes if we wish to.

Closes #26. It seems to work fine but due to 7.10 rush I don't have the
chance to do more exhaustive testing right now. The way the meta is
output (emphasis at the end of the whole comment) is fairly arbitrary
and subject to bikeshedding.

Note that this makes test for Bug310 fail due to interface version bump:
it can't find the docs for base with this interface version so it fails.
There is not much we can do to help this because it tests for ’built-in’
identifier, not something we can provide ourselves.

4 files changed, 59 insertions, 10 deletions

diff --git a/haddock-library/src/Documentation/Haddock/Doc.hs b/haddock-library/src/Documentation/Haddock/Doc.hs
index 1c20555d..fe8cf99b 100644
--- a/haddock-library/src/Documentation/Haddock/Doc.hs
+++ b/haddock-library/src/Documentation/Haddock/Doc.hs
@@ -1,12 +1,30 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
-module Documentation.Haddock.Doc (docParagraph, docAppend, docConcat) where
+module Documentation.Haddock.Doc (docParagraph, docAppend,
+                                  docConcat, metaDocConcat,
+                                  metaDocAppend, emptyMetaDoc) where
 
+import Data.Monoid (mempty, (<>))
 import Documentation.Haddock.Types
 import Data.Char (isSpace)
 
 docConcat :: [DocH mod id] -> DocH mod id
 docConcat = foldr docAppend DocEmpty
 
+-- | Like 'docConcat' but also joins the 'Meta' info.
+metaDocConcat :: [MetaDoc mod id] -> MetaDoc mod id
+metaDocConcat = foldr metaDocAppend emptyMetaDoc
+
+-- | We do something perhaps unexpected here and join the meta info
+-- in ‘reverse’: this results in the metadata from the ‘latest’
+-- paragraphs taking precedence.
+metaDocAppend :: MetaDoc mod id -> MetaDoc mod id -> MetaDoc mod id
+metaDocAppend (MetaDoc { _meta = m, _doc = d })
+              (MetaDoc { _meta = m', _doc = d' }) =
+  MetaDoc { _meta = m' <> m, _doc = d `docAppend` d' }
+
+emptyMetaDoc :: MetaDoc mod id
+emptyMetaDoc = MetaDoc { _meta = mempty, _doc = DocEmpty }
+
 docAppend :: DocH mod id -> DocH mod id -> DocH mod id
 docAppend (DocDefList ds1) (DocDefList ds2) = DocDefList (ds1++ds2)
 docAppend (DocDefList ds1) (DocAppend (DocDefList ds2) d) = DocAppend (DocDefList (ds1++ds2)) d
diff --git a/haddock-library/src/Documentation/Haddock/Parser.hs b/haddock-library/src/Documentation/Haddock/Parser.hs
index 1cc277b8..b88a8c7f 100644
--- a/haddock-library/src/Documentation/Haddock/Parser.hs
+++ b/haddock-library/src/Documentation/Haddock/Parser.hs
@@ -86,9 +86,11 @@ parse p = either err id . parseOnly (p <* endOfInput)
 -- | Main entry point to the parser. Appends the newline character
 -- to the input string.
 parseParas :: String -- ^ String to parse
-           -> (Maybe Version, DocH mod Identifier)
+           -> MetaDoc mod Identifier
 parseParas input = case parseParasState input of
-  (state, a) -> (parserStateSince state, a)
+  (state, a) -> MetaDoc { _meta = Meta { _version = parserStateSince state }
+                        , _doc = a
+                        }
 
 parseParasState :: String -> (ParserState, DocH mod Identifier)
 parseParasState = parse (p <* skipSpace) . encodeUtf8 . (++ "\n")
diff --git a/haddock-library/src/Documentation/Haddock/Types.hs b/haddock-library/src/Documentation/Haddock/Types.hs
index 92ddeb7e..6f22efb5 100644
--- a/haddock-library/src/Documentation/Haddock/Types.hs
+++ b/haddock-library/src/Documentation/Haddock/Types.hs
@@ -15,8 +15,28 @@
 module Documentation.Haddock.Types where
 
 import Data.Foldable
+import Data.Monoid
 import Data.Traversable
 
+-- | With the advent of 'Version', we may want to start attaching more
+-- meta-data to comments. We make a structure for this ahead of time
+-- so we don't have to gut half the core each time we want to add such
+-- info.
+newtype Meta = Meta { _version :: Maybe Version } deriving (Eq, Show)
+
+instance Monoid Meta where
+  mempty = Meta { _version = Nothing }
+  Meta { _version = v } `mappend` Meta { _version = v' } =
+    Meta { _version = v `mappend` v' }
+
+data MetaDoc mod id =
+  MetaDoc { _meta :: Meta
+          , _doc :: DocH mod id
+          } deriving (Eq, Show, Functor, Foldable, Traversable)
+
+overDoc :: (DocH a b -> DocH c d) -> MetaDoc a b -> MetaDoc c d
+overDoc f d = d { _doc = f $ _doc d }
+
 type Version = [Int]
 
 data Hyperlink = Hyperlink
diff --git a/haddock-library/test/Documentation/Haddock/ParserSpec.hs b/haddock-library/test/Documentation/Haddock/ParserSpec.hs
index 7b0ef78d..44ec2988 100644
--- a/haddock-library/test/Documentation/Haddock/ParserSpec.hs
+++ b/haddock-library/test/Documentation/Haddock/ParserSpec.hs
@@ -22,8 +22,8 @@ instance IsString (Doc String) where
 instance IsString a => IsString (Maybe a) where
   fromString = Just . fromString
 
-parseParas :: String -> (Maybe Version, Doc String)
-parseParas = fmap Parse.toRegular . Parse.parseParas
+parseParas :: String -> MetaDoc () String
+parseParas = overDoc Parse.toRegular . Parse.parseParas
 
 parseString :: String -> Doc String
 parseString = Parse.toRegular . Parse.parseString
@@ -358,7 +358,7 @@ spec = do
   describe "parseParas" $ do
     let infix 1 `shouldParseTo`
         shouldParseTo :: String -> Doc String -> Expectation
-        shouldParseTo input ast = snd (parseParas input) `shouldBe` ast
+        shouldParseTo input ast = _doc (parseParas input) `shouldBe` ast
 
     it "is total" $ do
       property $ \xs ->
@@ -366,13 +366,20 @@ spec = do
 
     context "when parsing @since" $ do
       it "adds specified version to the result" $ do
-        parseParas "@since 0.5.0" `shouldBe` (Just [0,5,0], DocEmpty)
+        parseParas "@since 0.5.0" `shouldBe`
+          MetaDoc { _meta = Meta { _version = Just [0,5,0] }
+                  , _doc = DocEmpty }
 
       it "ignores trailing whitespace" $ do
-        parseParas "@since 0.5.0 \t " `shouldBe` (Just [0,5,0], DocEmpty)
+        parseParas "@since 0.5.0 \t " `shouldBe`
+          MetaDoc { _meta = Meta { _version = Just [0,5,0] }
+                  , _doc = DocEmpty }
 
       it "does not allow trailing input" $ do
-        parseParas "@since 0.5.0 foo" `shouldBe` (Nothing, DocParagraph "@since 0.5.0 foo")
+        parseParas "@since 0.5.0 foo" `shouldBe`
+          MetaDoc { _meta = Meta { _version = Nothing }
+                  , _doc = DocParagraph "@since 0.5.0 foo" }
+
 
       context "when given multiple times" $ do
         it "gives last occurrence precedence" $ do
@@ -380,7 +387,9 @@ spec = do
               "@since 0.5.0"
             , "@since 0.6.0"
             , "@since 0.7.0"
-            ] `shouldBe` (Just [0,7,0], DocEmpty)
+            ] `shouldBe` MetaDoc { _meta = Meta { _version = Just [0,7,0] }
+                                 , _doc = DocEmpty }
+
 
     context "when parsing text paragraphs" $ do
       let filterSpecial = filter (`notElem` (".(=#-[*`\v\f\n\t\r\\\"'_/@<> " :: String))