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--------------------------------------------------------------------------------
-- | Parser utilities
module Hakyll.Core.Util.Parser
( metadataKey
) where
--------------------------------------------------------------------------------
import Control.Applicative ((<|>))
import Control.Monad (guard, mzero, void)
import qualified Text.Parsec as P
import Text.Parsec.String (Parser)
--------------------------------------------------------------------------------
metadataKey :: Parser String
metadataKey = do
-- Ensure trailing '-' binds to '$' if present.
let hyphon = P.try $ do
void $ P.char '-'
x <- P.lookAhead P.anyChar
guard $ x /= '$'
pure '-'
i <- (:) <$> P.letter <*> P.many (P.alphaNum <|> P.oneOf "_." <|> hyphon)
if i `elem` reservedKeys then mzero else return i
--------------------------------------------------------------------------------
reservedKeys :: [String]
reservedKeys = ["if", "else", "endif", "for", "sep", "endfor", "partial"]
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