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{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE Safe #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
-- |
-- Module : Text.Megaparsec.Internal
-- Copyright : © 2015–present Megaparsec contributors
-- © 2007 Paolo Martini
-- © 1999–2001 Daan Leijen
-- License : FreeBSD
--
-- Maintainer : Mark Karpov <markkarpov92@gmail.com>
-- Stability : experimental
-- Portability : portable
--
-- Internal definitions. Versioning rules do not apply here. Please do not
-- rely on these unless you really know what you're doing.
--
-- @since 6.5.0
module Text.Megaparsec.Internal
( -- * Data types
Hints (..),
Reply (..),
Consumption (..),
Result (..),
ParsecT (..),
-- * Helper functions
toHints,
withHints,
accHints,
refreshHints,
runParsecT,
withParsecT,
)
where
import Control.Applicative
import Control.Monad
import Control.Monad.Cont.Class
import Control.Monad.Error.Class
import qualified Control.Monad.Fail as Fail
import Control.Monad.Fix
import Control.Monad.IO.Class
import Control.Monad.Reader.Class
import Control.Monad.State.Class
import Control.Monad.Trans
import Control.Monad.Writer.Class
import Data.List.NonEmpty (NonEmpty (..))
import qualified Data.List.NonEmpty as NE
import Data.Proxy
import Data.Semigroup
import Data.Set (Set)
import qualified Data.Set as E
import Data.String (IsString (..))
import Text.Megaparsec.Class
import Text.Megaparsec.Error
import Text.Megaparsec.State
import Text.Megaparsec.Stream
----------------------------------------------------------------------------
-- Data types
-- | 'Hints' represent a collection of 'ErrorItem's to be included into
-- 'ParseError' (when it's a 'TrivialError') as “expected” message items
-- when a parser fails without consuming input right after successful parser
-- that produced the hints.
--
-- For example, without hints you could get:
--
-- >>> parseTest (many (char 'r') <* eof) "ra"
-- 1:2:
-- unexpected 'a'
-- expecting end of input
--
-- We're getting better error messages with the help of hints:
--
-- >>> parseTest (many (char 'r') <* eof) "ra"
-- 1:2:
-- unexpected 'a'
-- expecting 'r' or end of input
newtype Hints t = Hints (Set (ErrorItem t))
instance (Ord t) => Semigroup (Hints t) where
Hints xs <> Hints ys = Hints $ xs <> ys
instance (Ord t) => Monoid (Hints t) where
mempty = Hints mempty
-- | All information available after parsing. This includes consumption of
-- input, success (with the returned value) or failure (with the parse
-- error), and parser state at the end of parsing. 'Reply' can also be used
-- to resume parsing.
--
-- See also: 'Consumption', 'Result'.
data Reply e s a = Reply (State s e) Consumption (Result s e a)
deriving (Functor)
-- | Whether the input has been consumed or not.
--
-- See also: 'Result', 'Reply'.
data Consumption
= -- | Some part of input stream was consumed
Consumed
| -- | No input was consumed
NotConsumed
-- | Whether the parser has failed or not. On success we include the
-- resulting value, on failure we include a 'ParseError'.
--
-- See also: 'Consumption', 'Reply'.
data Result s e a
= -- | Parser succeeded (includes hints)
OK (Hints (Token s)) a
| -- | Parser failed
Error (ParseError s e)
deriving (Functor)
-- | @'ParsecT' e s m a@ is a parser with custom data component of error
-- @e@, stream type @s@, underlying monad @m@ and return type @a@.
newtype ParsecT e s m a = ParsecT
{ unParser ::
forall b.
State s e ->
(a -> State s e -> Hints (Token s) -> m b) -> -- consumed-OK
(ParseError s e -> State s e -> m b) -> -- consumed-error
(a -> State s e -> Hints (Token s) -> m b) -> -- empty-OK
(ParseError s e -> State s e -> m b) -> -- empty-error
m b
}
-- | @since 5.3.0
instance (Stream s, Semigroup a) => Semigroup (ParsecT e s m a) where
(<>) = liftA2 (<>)
{-# INLINE (<>) #-}
sconcat = fmap sconcat . sequence
{-# INLINE sconcat #-}
-- | @since 5.3.0
instance (Stream s, Monoid a) => Monoid (ParsecT e s m a) where
mempty = pure mempty
{-# INLINE mempty #-}
mappend = (<>)
{-# INLINE mappend #-}
mconcat = fmap mconcat . sequence
{-# INLINE mconcat #-}
-- | @since 6.3.0
instance
(a ~ Tokens s, IsString a, Eq a, Stream s, Ord e) =>
IsString (ParsecT e s m a)
where
fromString s = tokens (==) (fromString s)
instance Functor (ParsecT e s m) where
fmap = pMap
pMap :: (a -> b) -> ParsecT e s m a -> ParsecT e s m b
pMap f p = ParsecT $ \s cok cerr eok eerr ->
unParser p s (cok . f) cerr (eok . f) eerr
{-# INLINE pMap #-}
-- | 'pure' returns a parser that __succeeds__ without consuming input.
instance (Stream s) => Applicative (ParsecT e s m) where
pure = pPure
(<*>) = pAp
p1 *> p2 = p1 `pBind` const p2
p1 <* p2 = do x1 <- p1; void p2; return x1
pPure :: (Stream s) => a -> ParsecT e s m a
pPure x = ParsecT $ \s _ _ eok _ -> eok x s mempty
{-# INLINE pPure #-}
pAp ::
(Stream s) =>
ParsecT e s m (a -> b) ->
ParsecT e s m a ->
ParsecT e s m b
pAp m k = ParsecT $ \s cok cerr eok eerr ->
let mcok x s' hs =
unParser
k
s'
(cok . x)
cerr
(accHints hs (cok . x))
(withHints hs cerr)
meok x s' hs =
unParser
k
s'
(cok . x)
cerr
(accHints hs (eok . x))
(withHints hs eerr)
in unParser m s mcok cerr meok eerr
{-# INLINE pAp #-}
-- | 'empty' is a parser that __fails__ without consuming input.
instance (Ord e, Stream s) => Alternative (ParsecT e s m) where
empty = mzero
(<|>) = mplus
-- | 'return' returns a parser that __succeeds__ without consuming input.
instance (Stream s) => Monad (ParsecT e s m) where
return = pure
(>>=) = pBind
pBind ::
(Stream s) =>
ParsecT e s m a ->
(a -> ParsecT e s m b) ->
ParsecT e s m b
pBind m k = ParsecT $ \s cok cerr eok eerr ->
let mcok x s' hs =
unParser
(k x)
s'
cok
cerr
(accHints hs cok)
(withHints hs cerr)
meok x s' hs =
unParser
(k x)
s'
cok
cerr
(accHints hs eok)
(withHints hs eerr)
in unParser m s mcok cerr meok eerr
{-# INLINE pBind #-}
instance (Stream s) => Fail.MonadFail (ParsecT e s m) where
fail = pFail
pFail :: String -> ParsecT e s m a
pFail msg = ParsecT $ \s@(State _ o _ _) _ _ _ eerr ->
let d = E.singleton (ErrorFail msg)
in eerr (FancyError o d) s
{-# INLINE pFail #-}
instance (Stream s, MonadIO m) => MonadIO (ParsecT e s m) where
liftIO = lift . liftIO
instance (Stream s, MonadReader r m) => MonadReader r (ParsecT e s m) where
ask = lift ask
local f = hoistP (local f)
instance (Stream s, MonadState st m) => MonadState st (ParsecT e s m) where
get = lift get
put = lift . put
hoistP ::
(Monad m) =>
(m (Reply e s a) -> m (Reply e s b)) ->
ParsecT e s m a ->
ParsecT e s m b
hoistP h p = mkParsecT (h . runParsecT p)
-- | @since 9.5.0
instance (Stream s, MonadWriter w m) => MonadWriter w (ParsecT e s m) where
tell w = lift (tell w)
listen = hoistP (fmap (\(repl, w) -> fmap (,w) repl) . listen)
pass = hoistP $ \m -> pass $ do
Reply st consumption r <- m
let (r', ww') = case r of
OK hs (x, ww) -> (OK hs x, ww)
Error e -> (Error e, id)
return (Reply st consumption r', ww')
instance (Stream s, MonadCont m) => MonadCont (ParsecT e s m) where
callCC f = mkParsecT $ \s ->
callCC $ \c ->
runParsecT (f (\a -> mkParsecT $ \s' -> c (pack s' a))) s
where
pack s a = Reply s NotConsumed (OK mempty a)
instance (Stream s, MonadError e' m) => MonadError e' (ParsecT e s m) where
throwError = lift . throwError
p `catchError` h = mkParsecT $ \s ->
runParsecT p s `catchError` \e ->
runParsecT (h e) s
mkParsecT ::
(Monad m) =>
(State s e -> m (Reply e s a)) ->
ParsecT e s m a
mkParsecT k = ParsecT $ \s cok cerr eok eerr -> do
(Reply s' consumption result) <- k s
case consumption of
Consumed ->
case result of
OK hs x -> cok x s' hs
Error e -> cerr e s'
NotConsumed ->
case result of
OK hs x -> eok x s' hs
Error e -> eerr e s'
{-# INLINE mkParsecT #-}
pmkParsec ::
(State s e -> Reply e s a) ->
ParsecT e s m a
pmkParsec k = ParsecT $ \s cok cerr eok eerr ->
let (Reply s' consumption result) = k s
in case consumption of
Consumed ->
case result of
OK hs x -> cok x s' hs
Error e -> cerr e s'
NotConsumed ->
case result of
OK hs x -> eok x s' hs
Error e -> eerr e s'
{-# INLINE pmkParsec #-}
-- | 'mzero' is a parser that __fails__ without consuming input.
--
-- __Note__: strictly speaking, this instance is unlawful. The right
-- identity law does not hold, e.g. in general this is not true:
--
-- > v >> mzero = mero
--
-- However the following holds:
--
-- > try v >> mzero = mzero
instance (Ord e, Stream s) => MonadPlus (ParsecT e s m) where
mzero = pZero
mplus = pPlus
pZero :: ParsecT e s m a
pZero = ParsecT $ \s@(State _ o _ _) _ _ _ eerr ->
eerr (TrivialError o Nothing E.empty) s
{-# INLINE pZero #-}
pPlus ::
(Ord e, Stream s) =>
ParsecT e s m a ->
ParsecT e s m a ->
ParsecT e s m a
pPlus m n = ParsecT $ \s cok cerr eok eerr ->
let meerr err ms =
let ncerr err' s' = cerr (err' <> err) (longestMatch ms s')
neok x s' hs = eok x s' (toHints (stateOffset s') err <> hs)
neerr err' s' = eerr (err' <> err) (longestMatch ms s')
in unParser n s cok ncerr neok neerr
in unParser m s cok cerr eok meerr
{-# INLINE pPlus #-}
-- | From two states, return the one with the greater number of processed
-- tokens. If the numbers of processed tokens are equal, prefer the second
-- state.
longestMatch :: State s e -> State s e -> State s e
longestMatch s1@(State _ o1 _ _) s2@(State _ o2 _ _) =
case o1 `compare` o2 of
LT -> s2
EQ -> s2
GT -> s1
{-# INLINE longestMatch #-}
-- | @since 6.0.0
instance (Stream s, MonadFix m) => MonadFix (ParsecT e s m) where
mfix f = mkParsecT $ \s -> mfix $ \(~(Reply _ _ result)) -> do
let a = case result of
OK _ a' -> a'
Error _ -> error "mfix ParsecT"
runParsecT (f a) s
instance (Stream s) => MonadTrans (ParsecT e s) where
lift amb = ParsecT $ \s _ _ eok _ ->
amb >>= \a -> eok a s mempty
instance (Ord e, Stream s) => MonadParsec e s (ParsecT e s m) where
parseError = pParseError
label = pLabel
try = pTry
lookAhead = pLookAhead
notFollowedBy = pNotFollowedBy
withRecovery = pWithRecovery
observing = pObserving
eof = pEof
token = pToken
tokens = pTokens
takeWhileP = pTakeWhileP
takeWhile1P = pTakeWhile1P
takeP = pTakeP
getParserState = pGetParserState
updateParserState = pUpdateParserState
mkParsec = pmkParsec
pParseError ::
ParseError s e ->
ParsecT e s m a
pParseError e = ParsecT $ \s _ _ _ eerr -> eerr e s
{-# INLINE pParseError #-}
pLabel :: String -> ParsecT e s m a -> ParsecT e s m a
pLabel l p = ParsecT $ \s cok cerr eok eerr ->
let el = Label <$> NE.nonEmpty l
cok' x s' hs =
case el of
Nothing -> cok x s' (refreshHints hs Nothing)
Just _ -> cok x s' hs
eok' x s' hs = eok x s' (refreshHints hs el)
eerr' err = eerr $
case err of
(TrivialError pos us _) ->
TrivialError pos us (maybe E.empty E.singleton el)
_ -> err
in unParser p s cok' cerr eok' eerr'
{-# INLINE pLabel #-}
pTry :: ParsecT e s m a -> ParsecT e s m a
pTry p = ParsecT $ \s cok _ eok eerr ->
let eerr' err _ = eerr err s
in unParser p s cok eerr' eok eerr'
{-# INLINE pTry #-}
pLookAhead :: (Stream s) => ParsecT e s m a -> ParsecT e s m a
pLookAhead p = ParsecT $ \s _ cerr eok eerr ->
let eok' a _ _ = eok a s mempty
in unParser p s eok' cerr eok' eerr
{-# INLINE pLookAhead #-}
pNotFollowedBy :: (Stream s) => ParsecT e s m a -> ParsecT e s m ()
pNotFollowedBy p = ParsecT $ \s@(State input o _ _) _ _ eok eerr ->
let what = maybe EndOfInput (Tokens . nes . fst) (take1_ input)
unexpect u = TrivialError o (pure u) E.empty
cok' _ _ _ = eerr (unexpect what) s
cerr' _ _ = eok () s mempty
eok' _ _ _ = eerr (unexpect what) s
eerr' _ _ = eok () s mempty
in unParser p s cok' cerr' eok' eerr'
{-# INLINE pNotFollowedBy #-}
pWithRecovery ::
(Stream s) =>
(ParseError s e -> ParsecT e s m a) ->
ParsecT e s m a ->
ParsecT e s m a
pWithRecovery r p = ParsecT $ \s cok cerr eok eerr ->
let mcerr err ms =
let rcok x s' _ = cok x s' mempty
rcerr _ _ = cerr err ms
reok x s' _ = eok x s' (toHints (stateOffset s') err)
reerr _ _ = cerr err ms
in unParser (r err) ms rcok rcerr reok reerr
meerr err ms =
let rcok x s' _ = cok x s' (toHints (stateOffset s') err)
rcerr _ _ = eerr err ms
reok x s' _ = eok x s' (toHints (stateOffset s') err)
reerr _ _ = eerr err ms
in unParser (r err) ms rcok rcerr reok reerr
in unParser p s cok mcerr eok meerr
{-# INLINE pWithRecovery #-}
pObserving ::
(Stream s) =>
ParsecT e s m a ->
ParsecT e s m (Either (ParseError s e) a)
pObserving p = ParsecT $ \s cok _ eok _ ->
let cerr' err s' = cok (Left err) s' mempty
eerr' err s' = eok (Left err) s' (toHints (stateOffset s') err)
in unParser p s (cok . Right) cerr' (eok . Right) eerr'
{-# INLINE pObserving #-}
pEof :: forall e s m. (Stream s) => ParsecT e s m ()
pEof = ParsecT $ \s@(State input o pst de) _ _ eok eerr ->
case take1_ input of
Nothing -> eok () s mempty
Just (x, _) ->
let us = (pure . Tokens . nes) x
ps = E.singleton EndOfInput
in eerr
(TrivialError o us ps)
(State input o pst de)
{-# INLINE pEof #-}
pToken ::
forall e s m a.
(Stream s) =>
(Token s -> Maybe a) ->
Set (ErrorItem (Token s)) ->
ParsecT e s m a
pToken test ps = ParsecT $ \s@(State input o pst de) cok _ _ eerr ->
case take1_ input of
Nothing ->
let us = pure EndOfInput
in eerr (TrivialError o us ps) s
Just (c, cs) ->
case test c of
Nothing ->
let us = (Just . Tokens . nes) c
in eerr
(TrivialError o us ps)
(State input o pst de)
Just x ->
cok x (State cs (o + 1) pst de) mempty
{-# INLINE pToken #-}
pTokens ::
forall e s m.
(Stream s) =>
(Tokens s -> Tokens s -> Bool) ->
Tokens s ->
ParsecT e s m (Tokens s)
pTokens f tts = ParsecT $ \s@(State input o pst de) cok _ eok eerr ->
let pxy = Proxy :: Proxy s
unexpect pos' u =
let us = pure u
ps = (E.singleton . Tokens . NE.fromList . chunkToTokens pxy) tts
in TrivialError pos' us ps
len = chunkLength pxy tts
in case takeN_ len input of
Nothing ->
eerr (unexpect o EndOfInput) s
Just (tts', input') ->
if f tts tts'
then
let st = State input' (o + len) pst de
in if chunkEmpty pxy tts
then eok tts' st mempty
else cok tts' st mempty
else
let ps = (Tokens . NE.fromList . chunkToTokens pxy) tts'
in eerr (unexpect o ps) (State input o pst de)
{-# INLINE pTokens #-}
pTakeWhileP ::
forall e s m.
(Stream s) =>
Maybe String ->
(Token s -> Bool) ->
ParsecT e s m (Tokens s)
pTakeWhileP ml f = ParsecT $ \(State input o pst de) cok _ eok _ ->
let pxy = Proxy :: Proxy s
(ts, input') = takeWhile_ f input
len = chunkLength pxy ts
hs =
case ml >>= NE.nonEmpty of
Nothing -> mempty
Just l -> (Hints . E.singleton . Label) l
in if chunkEmpty pxy ts
then eok ts (State input' (o + len) pst de) hs
else cok ts (State input' (o + len) pst de) hs
{-# INLINE pTakeWhileP #-}
pTakeWhile1P ::
forall e s m.
(Stream s) =>
Maybe String ->
(Token s -> Bool) ->
ParsecT e s m (Tokens s)
pTakeWhile1P ml f = ParsecT $ \(State input o pst de) cok _ _ eerr ->
let pxy = Proxy :: Proxy s
(ts, input') = takeWhile_ f input
len = chunkLength pxy ts
el = Label <$> (ml >>= NE.nonEmpty)
hs =
case el of
Nothing -> mempty
Just l -> (Hints . E.singleton) l
in if chunkEmpty pxy ts
then
let us = pure $
case take1_ input of
Nothing -> EndOfInput
Just (t, _) -> Tokens (nes t)
ps = maybe E.empty E.singleton el
in eerr
(TrivialError o us ps)
(State input o pst de)
else cok ts (State input' (o + len) pst de) hs
{-# INLINE pTakeWhile1P #-}
pTakeP ::
forall e s m.
(Stream s) =>
Maybe String ->
Int ->
ParsecT e s m (Tokens s)
pTakeP ml n' = ParsecT $ \s@(State input o pst de) cok _ _ eerr ->
let n = max 0 n'
pxy = Proxy :: Proxy s
el = Label <$> (ml >>= NE.nonEmpty)
ps = maybe E.empty E.singleton el
in case takeN_ n input of
Nothing ->
eerr (TrivialError o (pure EndOfInput) ps) s
Just (ts, input') ->
let len = chunkLength pxy ts
in if len /= n
then
eerr
(TrivialError (o + len) (pure EndOfInput) ps)
(State input o pst de)
else cok ts (State input' (o + len) pst de) mempty
{-# INLINE pTakeP #-}
pGetParserState :: (Stream s) => ParsecT e s m (State s e)
pGetParserState = ParsecT $ \s _ _ eok _ -> eok s s mempty
{-# INLINE pGetParserState #-}
pUpdateParserState :: (Stream s) => (State s e -> State s e) -> ParsecT e s m ()
pUpdateParserState f = ParsecT $ \s _ _ eok _ -> eok () (f s) mempty
{-# INLINE pUpdateParserState #-}
nes :: a -> NonEmpty a
nes x = x :| []
{-# INLINE nes #-}
----------------------------------------------------------------------------
-- Helper functions
-- | Convert a 'ParseError' record into 'Hints'.
toHints ::
(Stream s) =>
-- | Current offset in input stream
Int ->
-- | Parse error to convert
ParseError s e ->
Hints (Token s)
toHints streamPos = \case
TrivialError errOffset _ ps ->
-- NOTE This is important to check here that the error indeed has
-- happened at the same position as current position of stream because
-- there might have been backtracking with 'try' and in that case we
-- must not convert such a parse error to hints.
if streamPos == errOffset
then Hints (if E.null ps then E.empty else ps)
else mempty
FancyError _ _ -> mempty
{-# INLINE toHints #-}
-- | @'withHints' hs c@ makes “error” continuation @c@ use given hints @hs@.
--
-- __Note__ that if resulting continuation gets 'ParseError' that has custom
-- data in it, hints are ignored.
withHints ::
(Stream s) =>
-- | Hints to use
Hints (Token s) ->
-- | Continuation to influence
(ParseError s e -> State s e -> m b) ->
-- | First argument of resulting continuation
ParseError s e ->
-- | Second argument of resulting continuation
State s e ->
m b
withHints (Hints ps') c e =
case e of
TrivialError pos us ps -> c (TrivialError pos us (E.union ps ps'))
_ -> c e
{-# INLINE withHints #-}
-- | @'accHints' hs c@ results in “OK” continuation that will add given
-- hints @hs@ to third argument of original continuation @c@.
accHints ::
(Stream s) =>
-- | 'Hints' to add
Hints (Token s) ->
-- | An “OK” continuation to alter
(a -> State s e -> Hints (Token s) -> m b) ->
-- | Altered “OK” continuation
(a -> State s e -> Hints (Token s) -> m b)
accHints hs1 c x s hs2 = c x s (hs1 <> hs2)
{-# INLINE accHints #-}
-- | Replace the hints with the given 'ErrorItem' (or delete it if 'Nothing'
-- is given). This is used in the 'label' primitive.
refreshHints :: Hints t -> Maybe (ErrorItem t) -> Hints t
refreshHints (Hints _) Nothing = Hints E.empty
refreshHints (Hints hs) (Just m) =
if E.null hs
then Hints hs
else Hints (E.singleton m)
{-# INLINE refreshHints #-}
-- | Low-level unpacking of the 'ParsecT' type.
runParsecT ::
(Monad m) =>
-- | Parser to run
ParsecT e s m a ->
-- | Initial state
State s e ->
m (Reply e s a)
runParsecT p s = unParser p s cok cerr eok eerr
where
cok a s' hs = return $ Reply s' Consumed (OK hs a)
cerr err s' = return $ Reply s' Consumed (Error err)
eok a s' hs = return $ Reply s' NotConsumed (OK hs a)
eerr err s' = return $ Reply s' NotConsumed (Error err)
-- | Transform any custom errors thrown by the parser using the given
-- function. Similar in function and purpose to @withExceptT@.
--
-- __Note__ that the inner parser will start with an empty collection of
-- “delayed” 'ParseError's. Any delayed 'ParseError's produced in the inner
-- parser will be lifted by applying the provided function and added to the
-- collection of delayed parse errors of the outer parser.
--
-- @since 7.0.0
withParsecT ::
forall e e' s m a.
(Ord e') =>
(e -> e') ->
-- | Inner parser
ParsecT e s m a ->
-- | Outer parser
ParsecT e' s m a
withParsecT f p =
ParsecT $ \s cok cerr eok eerr ->
let s' =
s
{ stateParseErrors = []
}
adjustState :: State s e -> State s e'
adjustState st =
st
{ stateParseErrors =
(mapParseError f <$> stateParseErrors st)
++ stateParseErrors s
}
cok' x st hs = cok x (adjustState st) hs
cerr' e st = cerr (mapParseError f e) (adjustState st)
eok' x st hs = eok x (adjustState st) hs
eerr' e st = eerr (mapParseError f e) (adjustState st)
in unParser p s' cok' cerr' eok' eerr'
{-# INLINE withParsecT #-}
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