coot/multiple package (ghc-head) (#1419)

* FromJSON class

Aeson style FromJSON class with Parsec based json parser.

* doc-index.json file for multiple packages

When creating haddock summary page for multiple packages render
doc-index.json file using contents of all found 'doc-index.json' files.

* Render doc-index.json

When rendering html, render doc-index.json file independently of
maybe_index_url option.  doc-index.json file is useful now even if
maybe_index_url is not `Nothing`.

* base url option

New `Flag_BaseURL` which configures from where static files are loaded
(--base-url).  If given and not equal "." static files are not coppied,
as this indicates that they are not read from the the directory where
we'd copy them.  The default value is ".".

1 files changed, 356 insertions, 22 deletions

diff --git a/haddock-api/src/Haddock/Utils/Json.hs b/haddock-api/src/Haddock/Utils/Json.hs
index 2270a547..d5d5ae02 100644
--- a/haddock-api/src/Haddock/Utils/Json.hs
+++ b/haddock-api/src/Haddock/Utils/Json.hs
@@ -1,4 +1,6 @@
+{-# LANGUAGE ExplicitForAll    #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RankNTypes        #-}
 
 -- | Minimal JSON / RFC 7159 support
 --
@@ -12,35 +14,53 @@ module Haddock.Utils.Json
     , encodeToString
     , encodeToBuilder
     , ToJSON(toJSON)
+
+    , Parser(..)
+    , Result(..)
+    , FromJSON(parseJSON)
+    , withObject
+    , withArray
+    , withString
+    , withDouble
+    , withBool
+    , fromJSON
+    , parse
+    , parseEither
+    , (.:)
+    , (.:?)
+    , decode
+    , decodeWith
+    , eitherDecode
+    , eitherDecodeWith
+    , decodeFile
+    , eitherDecodeFile
     )
     where
 
+import Control.Applicative (Alternative (..))
+import Control.Monad (MonadPlus (..), zipWithM, (>=>))
+import qualified Control.Monad as Monad
+import qualified Control.Monad.Fail as Fail
+
+import qualified Data.ByteString.Lazy as BSL
+import Data.ByteString.Builder (Builder)
+import qualified Data.ByteString.Builder as BB
 import Data.Char
 import Data.Int
-import Data.String
 import Data.Word
 import Data.List (intersperse)
 import Data.Monoid
 
-import Data.ByteString.Builder (Builder)
-import qualified Data.ByteString.Builder as BB
+import GHC.Natural
 
 -- TODO: We may want to replace 'String' with 'Text' or 'ByteString'
 
--- | A JSON value represented as a Haskell value.
-data Value = Object !Object
-           | Array  [Value]
-           | String  String
-           | Number !Double
-           | Bool   !Bool
-           | Null
-           deriving (Eq, Read, Show)
+import qualified Text.Parsec.ByteString.Lazy as Parsec.Lazy
+import qualified Text.ParserCombinators.Parsec as Parsec
 
--- | A key\/value pair for an 'Object'
-type Pair = (String, Value)
+import Haddock.Utils.Json.Types
+import Haddock.Utils.Json.Parser
 
--- | A JSON \"object\" (key/value map).
-type Object = [Pair]
 
 infixr 8 .=
 
@@ -48,13 +68,6 @@ infixr 8 .=
 (.=) :: ToJSON v => String -> v -> Pair
 k .= v  = (k, toJSON v)
 
--- | Create a 'Value' from a list of name\/value 'Pair's.
-object :: [Pair] -> Value
-object = Object
-
-instance IsString Value where
-  fromString = String
-
 
 -- | A type that can be converted to JSON.
 class ToJSON a where
@@ -223,3 +236,324 @@ escapeString s
 
     -- unescaped = %x20-21 / %x23-5B / %x5D-10FFFF
     needsEscape c = ord c < 0x20 || c `elem` ['\\','"']
+
+------------------------------------------------------------------------------
+-- FromJSON
+
+-- | Elements of a JSON path used to describe the location of an
+-- error.
+data JSONPathElement
+  = Key String
+  -- ^ JSON path element of a key into an object,
+  -- \"object.key\".
+  | Index !Int
+  -- ^ JSON path element of an index into an
+  -- array, \"array[index]\".
+  deriving (Eq, Show, Ord)
+
+type JSONPath = [JSONPathElement]
+
+-- | Failure continuation.
+type Failure f r   = JSONPath -> String -> f r
+
+-- | Success continuation.
+type Success a f r = a -> f r
+
+newtype Parser a = Parser {
+      runParser :: forall f r.
+                   JSONPath
+                -> Failure f r
+                -> Success a f r
+                -> f r
+    }
+
+modifyFailure :: (String -> String) -> Parser a -> Parser a
+modifyFailure f (Parser p) = Parser $ \path kf ks ->
+    p path (\p' m -> kf p' (f m)) ks
+
+prependFailure :: String -> Parser a -> Parser a
+prependFailure = modifyFailure . (++)
+
+prependContext :: String -> Parser a -> Parser a
+prependContext name = prependFailure ("parsing " ++ name ++ " failed, ")
+
+typeMismatch :: String -> Value -> Parser a
+typeMismatch expected actual =
+    fail $ "expected " ++ expected ++ ", but encountered " ++ typeOf actual
+
+instance Monad.Monad Parser where
+    m >>= g = Parser $ \path kf ks ->
+      runParser m path kf
+                       (\a -> runParser (g a) path kf ks)
+    return = pure
+
+instance Fail.MonadFail Parser where
+    fail msg = Parser $ \path kf _ks -> kf (reverse path) msg
+
+instance Functor Parser where
+    fmap f m = Parser $ \path kf ks ->
+      let ks' a = ks (f a)
+      in runParser m path kf ks'
+
+instance Applicative Parser where
+    pure a = Parser $ \_path _kf ks -> ks a
+    (<*>) = apP
+
+instance Alternative Parser where
+    empty = fail "empty"
+    (<|>) = mplus
+
+instance MonadPlus Parser where
+    mzero = fail "mzero"
+    mplus a b = Parser $ \path kf ks ->
+      runParser a path (\_ _ -> runParser b path kf ks) ks
+
+instance Semigroup (Parser a) where
+    (<>) = mplus
+
+instance Monoid (Parser a) where
+    mempty  = fail "mempty"
+    mappend = (<>)
+
+apP :: Parser (a -> b) -> Parser a -> Parser b
+apP d e = do
+  b <- d
+  b <$> e
+
+(<?>) :: Parser a -> JSONPathElement -> Parser a
+p <?> pathElem = Parser $ \path kf ks -> runParser p (pathElem:path) kf ks
+
+parseIndexedJSON :: (Value -> Parser a) -> Int -> Value -> Parser a
+parseIndexedJSON p idx value = p value <?> Index idx
+
+unexpected :: Value -> Parser a
+unexpected actual = fail $ "unexpected " ++ typeOf actual
+
+withObject :: String -> (Object -> Parser a) -> Value -> Parser a
+withObject _    f (Object obj) = f obj
+withObject name _ v            = prependContext name (typeMismatch "Object" v)
+
+withArray :: String -> ([Value] -> Parser a) -> Value -> Parser a
+withArray _    f (Array arr) = f arr
+withArray name _ v           = prependContext name (typeMismatch "Array" v)
+
+withString :: String -> (String -> Parser a) -> Value -> Parser a
+withString _    f (String txt) = f txt
+withString name _ v            = prependContext name (typeMismatch "String" v)
+
+withDouble :: String -> (Double -> Parser a) -> Value -> Parser a
+withDouble _    f (Number duble) = f duble
+withDouble name _ v              = prependContext name (typeMismatch "Number" v)
+
+withBool :: String -> (Bool -> Parser a) -> Value -> Parser a
+withBool _    f (Bool arr) = f arr
+withBool name _ v          = prependContext name (typeMismatch "Boolean" v)
+
+class FromJSON a where
+    parseJSON     :: Value -> Parser a
+
+    parseJSONList :: Value -> Parser [a]
+    parseJSONList = withArray "[]" (zipWithM (parseIndexedJSON parseJSON) [0..])
+
+instance FromJSON Bool where
+    parseJSON (Bool b)  = pure b
+    parseJSON v = typeMismatch "Bool" v
+
+instance FromJSON () where
+    parseJSON =
+      withArray "()" $ \v ->
+        if null v
+          then pure ()
+          else prependContext "()" $ fail "expected an empty array"
+
+instance FromJSON Char where
+    parseJSON = withString "Char" parseChar
+
+    parseJSONList (String s) = pure s
+    parseJSONList v = typeMismatch "String" v
+
+parseChar :: String -> Parser Char
+parseChar t =
+    if length t == 1
+      then pure $ head t
+      else prependContext "Char" $ fail "expected a string of length 1"
+
+parseRealFloat :: RealFloat a => String -> Value -> Parser a
+parseRealFloat _    (Number s) = pure $ realToFrac s
+parseRealFloat _    Null       = pure (0/0)
+parseRealFloat name v          = prependContext name (unexpected v)
+
+instance FromJSON Double where
+    parseJSON = parseRealFloat "Double"
+
+instance FromJSON Float where
+    parseJSON = parseRealFloat "Float"
+
+parseNatural :: Integer -> Parser Natural
+parseNatural integer =
+    if integer < 0 then
+        fail $ "parsing Natural failed, unexpected negative number " <> show integer
+    else
+        pure $ fromIntegral integer
+
+parseIntegralFromDouble :: Integral a => Double -> Parser a
+parseIntegralFromDouble d =
+    let r = toRational d
+        x = truncate r
+    in if toRational x == r
+         then pure $ x
+         else fail $ "unexpected floating number " <> show d
+
+parseIntegral :: Integral a => String -> Value -> Parser a
+parseIntegral name = withDouble name parseIntegralFromDouble
+
+instance FromJSON Integer where
+    parseJSON = parseIntegral "Integer"
+
+instance FromJSON Natural where
+    parseJSON = withDouble "Natural"
+                  (parseIntegralFromDouble >=> parseNatural)
+
+instance FromJSON Int where
+    parseJSON = parseIntegral "Int"
+
+instance FromJSON Int8 where
+    parseJSON = parseIntegral "Int8"
+
+instance FromJSON Int16 where
+    parseJSON = parseIntegral "Int16"
+
+instance FromJSON Int32 where
+    parseJSON = parseIntegral "Int32"
+
+instance FromJSON Int64 where
+    parseJSON = parseIntegral "Int64"
+
+instance FromJSON Word where
+    parseJSON = parseIntegral "Word"
+
+instance FromJSON Word8 where
+    parseJSON = parseIntegral "Word8"
+
+instance FromJSON Word16 where
+    parseJSON = parseIntegral "Word16"
+
+instance FromJSON Word32 where
+    parseJSON = parseIntegral "Word32"
+
+instance FromJSON Word64 where
+    parseJSON = parseIntegral "Word64"
+
+instance FromJSON a => FromJSON [a] where
+    parseJSON = parseJSONList
+
+data Result a = Error String
+              | Success a
+                deriving (Eq, Show)
+
+fromJSON :: FromJSON a => Value -> Result a
+fromJSON = parse parseJSON
+
+parse :: (a -> Parser b) -> a -> Result b
+parse m v = runParser (m v) [] (const Error) Success
+
+parseEither :: (a -> Parser b) -> a -> Either String b
+parseEither m v = runParser (m v) [] onError Right
+  where onError path msg = Left (formatError path msg)
+
+formatError :: JSONPath -> String -> String
+formatError path msg = "Error in " ++ formatPath path ++ ": " ++ msg
+
+formatPath :: JSONPath -> String
+formatPath path = "$" ++ formatRelativePath path
+
+formatRelativePath :: JSONPath -> String
+formatRelativePath path = format "" path
+  where
+    format :: String -> JSONPath -> String
+    format pfx []                = pfx
+    format pfx (Index idx:parts) = format (pfx ++ "[" ++ show idx ++ "]") parts
+    format pfx (Key key:parts)   = format (pfx ++ formatKey key) parts
+
+    formatKey :: String -> String
+    formatKey key
+       | isIdentifierKey key = "." ++ key
+       | otherwise           = "['" ++ escapeKey key ++ "']"
+
+    isIdentifierKey :: String -> Bool
+    isIdentifierKey []     = False
+    isIdentifierKey (x:xs) = isAlpha x && all isAlphaNum xs
+
+    escapeKey :: String -> String
+    escapeKey = concatMap escapeChar
+
+    escapeChar :: Char -> String
+    escapeChar '\'' = "\\'"
+    escapeChar '\\' = "\\\\"
+    escapeChar c    = [c]
+
+explicitParseField :: (Value -> Parser a) -> Object -> String -> Parser a
+explicitParseField p obj key =
+    case key `lookup` obj of
+      Nothing -> fail $ "key " ++ key ++ " not found"
+      Just v  -> p v <?> Key key
+
+(.:) :: FromJSON a => Object -> String -> Parser a
+(.:) = explicitParseField parseJSON
+
+explicitParseFieldMaybe :: (Value -> Parser a) -> Object -> String -> Parser (Maybe a)
+explicitParseFieldMaybe p obj key =
+    case key `lookup` obj of
+      Nothing -> pure Nothing
+      Just v  -> Just <$> p v <?> Key key
+
+(.:?) :: FromJSON a => Object -> String -> Parser (Maybe a)
+(.:?) = explicitParseFieldMaybe parseJSON
+
+
+decodeWith :: (Value -> Result a) -> BSL.ByteString -> Maybe a
+decodeWith decoder bsl =
+   case Parsec.parse parseJSONValue "<input>" bsl of
+     Left  _    -> Nothing
+     Right json ->
+       case decoder json of
+         Success a -> Just a
+         Error _   -> Nothing
+
+decode :: FromJSON a => BSL.ByteString -> Maybe a
+decode = decodeWith fromJSON
+
+eitherDecodeWith :: (Value -> Result a) -> BSL.ByteString -> Either String a
+eitherDecodeWith decoder bsl =
+    case Parsec.parse parseJSONValue "<input>" bsl of
+      Left parsecError -> Left (show parsecError)
+      Right json ->
+        case decoder json of
+          Success a -> Right a
+          Error err -> Left  err
+
+eitherDecode :: FromJSON a => BSL.ByteString -> Either String a
+eitherDecode = eitherDecodeWith fromJSON
+
+
+decodeFile :: FromJSON a => FilePath -> IO (Maybe a)
+decodeFile filePath = do
+    parsecResult <- Parsec.Lazy.parseFromFile parseJSONValue filePath
+    case parsecResult of
+      Right r ->
+        case fromJSON r of
+          Success a -> return (Just a)
+          Error   _ -> return Nothing
+      Left _ -> return Nothing
+
+
+eitherDecodeFile :: FromJSON a => FilePath -> IO (Either String a)
+eitherDecodeFile filePath = do
+    parsecResult <- Parsec.Lazy.parseFromFile parseJSONValue filePath
+    case parsecResult of
+      Right r ->
+        case fromJSON r of
+          Success a -> return (Right a)
+          Error err -> return (Left err)
+      Left err -> return $ Left (show err)
+