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Diffstat (limited to 'haddock-library/src/Documentation/Haddock/Parser/Identifier.hs')
| -rw-r--r-- | haddock-library/src/Documentation/Haddock/Parser/Identifier.hs | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/haddock-library/src/Documentation/Haddock/Parser/Identifier.hs b/haddock-library/src/Documentation/Haddock/Parser/Identifier.hs new file mode 100644 index 00000000..b8afb951 --- /dev/null +++ b/haddock-library/src/Documentation/Haddock/Parser/Identifier.hs @@ -0,0 +1,160 @@ +{-# LANGUAGE BangPatterns #-} +{-# LANGUAGE ViewPatterns #-} +-- | +-- Module : Documentation.Haddock.Parser.Identifier +-- Copyright : (c) Alec Theriault 2019, +-- License : BSD-like +-- +-- Maintainer : haddock@projects.haskell.org +-- Stability : experimental +-- Portability : portable +-- +-- Functionality for parsing identifiers and operators + +module Documentation.Haddock.Parser.Identifier ( + Identifier(..), + parseValid, +) where + +import Documentation.Haddock.Types ( Namespace(..) ) +import Documentation.Haddock.Parser.Monad +import qualified Text.Parsec as Parsec +import Text.Parsec.Pos ( updatePosChar ) +import Text.Parsec ( State(..) + , getParserState, setParserState ) + +import Data.Text (Text) +import qualified Data.Text as T + +import Data.Char (isAlpha, isAlphaNum) +import Control.Monad (guard) +import Data.Maybe +import CompatPrelude + +-- | Identifier string surrounded with namespace, opening, and closing quotes/backticks. +data Identifier = Identifier !Namespace !Char String !Char + deriving (Show, Eq) + +parseValid :: Parser Identifier +parseValid = do + s@State{ stateInput = inp, statePos = pos } <- getParserState + + case takeIdentifier inp of + Nothing -> Parsec.parserFail "parseValid: Failed to match a valid identifier" + Just (ns, op, ident, cl, inp') -> + let posOp = updatePosChar pos op + posIdent = T.foldl updatePosChar posOp ident + posCl = updatePosChar posIdent cl + s' = s{ stateInput = inp', statePos = posCl } + in setParserState s' $> Identifier ns op (T.unpack ident) cl + + +-- | Try to parse a delimited identifier off the front of the given input. +-- +-- This tries to match as many valid Haskell identifiers/operators as possible, +-- to the point of sometimes accepting invalid things (ex: keywords). Some +-- considerations: +-- +-- - operators and identifiers can have module qualifications +-- - operators can be wrapped in parens (for prefix) +-- - identifiers can be wrapped in backticks (for infix) +-- - delimiters are backticks or regular ticks +-- - since regular ticks are also valid in identifiers, we opt for the +-- longest successful parse +-- +-- This function should make /O(1)/ allocations +takeIdentifier :: Text -> Maybe (Namespace, Char, Text, Char, Text) +takeIdentifier input = listToMaybe $ do + + -- Optional namespace + let (ns, input') = case T.uncons input of + Just ('v', i) -> (Value, i) + Just ('t', i) -> (Type, i) + _ -> (None, input) + + -- Opening tick + (op, input'') <- maybeToList (T.uncons input') + guard (op == '\'' || op == '`') + + -- Identifier/operator + (ident, input''') <- wrapped input'' + + -- Closing tick + (cl, input'''') <- maybeToList (T.uncons input''') + guard (cl == '\'' || cl == '`') + + return (ns, op, ident, cl, input'''') + + where + + -- | Parse out a wrapped, possibly qualified, operator or identifier + wrapped t = do + (c, t' ) <- maybeToList (T.uncons t) + -- Tuples + case c of + '(' | Just (c', _) <- T.uncons t' + , c' == ',' || c' == ')' + -> do let (commas, t'') = T.span (== ',') t' + (')', t''') <- maybeToList (T.uncons t'') + return (T.take (T.length commas + 2) t, t''') + + -- Parenthesized + '(' -> do (n, t'' ) <- general False 0 [] t' + (')', t''') <- maybeToList (T.uncons t'') + return (T.take (n + 2) t, t''') + + -- Backticked + '`' -> do (n, t'' ) <- general False 0 [] t' + ('`', t''') <- maybeToList (T.uncons t'') + return (T.take (n + 2) t, t''') + + -- Unadorned + _ -> do (n, t'' ) <- general False 0 [] t + return (T.take n t, t'') + + -- | Parse out a possibly qualified operator or identifier + general :: Bool -- ^ refuse inputs starting with operators + -> Int -- ^ total characters \"consumed\" so far + -> [(Int, Text)] -- ^ accumulated results + -> Text -- ^ current input + -> [(Int, Text)] -- ^ total characters parsed & what remains + general !identOnly !i acc t + -- Starts with an identifier (either just an identifier, or a module qual) + | Just (n, rest) <- identLike t + = if T.null rest + then acc + else case T.head rest of + '`' -> (n + i, rest) : acc + ')' -> (n + i, rest) : acc + '.' -> general False (n + i + 1) acc (T.tail rest) + '\'' -> let (m, rest') = quotes rest + in general True (n + m + 1 + i) ((n + m + i, rest') : acc) (T.tail rest') + _ -> acc + + -- An operator + | Just (n, rest) <- optr t + , not identOnly + = (n + i, rest) : acc + + -- Anything else + | otherwise + = acc + + -- | Parse an identifier off the front of the input + identLike t + | T.null t = Nothing + | isAlpha (T.head t) || '_' == T.head t + = let !(idt, rest) = T.span (\c -> isAlphaNum c || c == '_') t + !(octos, rest') = T.span (== '#') rest + in Just (T.length idt + T.length octos, rest') + | otherwise = Nothing + + -- | Parse all but the last quote off the front of the input + -- PRECONDITION: T.head t == '\'' + quotes :: Text -> (Int, Text) + quotes t = let !n = T.length (T.takeWhile (== '\'') t) - 1 + in (n, T.drop n t) + + -- | Parse an operator off the front of the input + optr t = let !(op, rest) = T.span isSymbolChar t + in if T.null op then Nothing else Just (T.length op, rest) |