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Improve Distribution.Lex.tokenizeQuotedWords #12187

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Improve Distribution.Lex.tokenizeQuotedWords
Bodigrim Jul 30, 2026
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Add comment with examples for tokenizeQuotedWords
Bodigrim Aug 13, 2026
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55 changes: 26 additions & 29 deletions Cabal/src/Distribution/Lex.hs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@
-----------------------------------------------------------------------------

-- |
-- Module : Distribution.Lex
-- Copyright : Ben Gamari 2015-2019
Expand All @@ -12,39 +10,38 @@ module Distribution.Lex
( tokenizeQuotedWords
) where

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

-- | A simple parser supporting quoted strings.
--
-- Please be aware that this will only split strings when seeing whitespace
-- outside of quotation marks, i.e, @"foo\"bar baz\"qux quux"@ will be
-- converted to @["foobar bazqux", "quux"]@.
-- outside of quotation marks;
--
-- > foo"bar baz"qux quux
--
-- >>> tokenizeQuotedWords "foo\"bar baz\"qux quux"
-- ["foobar bazqux","quux"]
--
-- This behavior can be useful when parsing text like
-- @"ghc-options: -Wl,\"some option with spaces\""@, for instance.
-- This behavior can be useful when parsing text like;
--
-- > ghc-options: -Wl,"some option with spaces"
--
-- >>> tokenizeQuotedWords "ghc-options: -Wl,\"some option with spaces\""
-- ["ghc-options:","-Wl,some option with spaces"]
tokenizeQuotedWords :: String -> [String]
tokenizeQuotedWords = filter (not . null) . go False mempty
tokenizeQuotedWords xs = repack $ foldr alg (const ([] :| [])) xs False
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 <> singleton c) cs
repack :: NonEmpty String -> [String]
repack (zs :| acc) = if null zs then acc else zs : acc

alg
:: Char -- current character
-> (Bool -> NonEmpty String) -- continuation, depending on whether we are in a quoted region or not
-> Bool -- are we in a quoted region?
-> NonEmpty String
alg '"' rest mode = rest (not mode)
alg c rest False
| isSpace c = [] :| repack (rest False)
alg c rest mode = case rest mode of
w :| ws -> (c : w) :| ws
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