Distribution/Lex.hs

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Lex
    -- Copyright   :  Ben Gamari 2015-2019
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This module contains a simple lexer supporting quoted strings

    module Distribution.Lex (
            tokenizeQuotedWords
     ) where

    import Prelude ()
    import Distribution.Compat.Prelude
    import Distribution.Compat.DList

    tokenizeQuotedWords :: String -> [String]
    tokenizeQuotedWords = filter (not . null) . go False mempty
      where
        go :: Bool        -- ^ in quoted region
           -> DList Char  -- ^ accumulator
           -> String      -- ^ string to be parsed
           -> [String]    -- ^ parse result
        go _ accum []
          | [] <- accum' = []
          | otherwise    = [accum']
          where accum' = runDList accum

        go False  accum (c:cs)
          | isSpace c = runDList accum : go False mempty cs
          | c == '"'  = go True accum cs

        go True   accum (c:cs)
          | c == '"'  = go False accum cs

        go quoted accum (c:cs)
                      = go quoted (accum `mappend` singleton c) cs