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Fix choice error behavior #168

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Merged
merged 1 commit into from
Mar 29, 2022
Merged

Fix choice error behavior #168

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8 changes: 6 additions & 2 deletions src/Text/Parsing/Parser/Combinators.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ import Data.Function.Uncurried (mkFn2, mkFn5, runFn2, runFn5)
import Data.List (List(..), many, manyRec, reverse, (:))
import Data.List.NonEmpty (NonEmptyList, cons')
import Data.List.NonEmpty as NEL
import Data.Maybe (Maybe(..))
import Data.Maybe (Maybe(..), fromMaybe)
import Data.Tuple (Tuple(..))
import Data.Tuple.Nested (type (/\), (/\))
import Data.Unfoldable (replicateA)
Expand Down Expand Up @@ -442,7 +442,11 @@ chainr1Rec p f = do

-- | Parse one of a set of alternatives.
choice :: forall f m s a. Foldable f => f (ParserT s m a) -> ParserT s m a
choice = foldr (<|>) empty
choice = fromMaybe empty <<< foldr go Nothing
where
go p1 = case _ of
Nothing -> Just p1
Just p2 -> Just (p1 <|> p2)

-- | Skip many instances of a phrase.
skipMany :: forall s a m. ParserT s m a -> ParserT s m Unit
Expand Down
12 changes: 11 additions & 1 deletion test/Main.purs
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Expand Up @@ -22,7 +22,7 @@ import Effect.Console (logShow)
import Partial.Unsafe (unsafePartial)
import Test.Assert (assert')
import Text.Parsing.Parser (ParseError(..), Parser, ParserT, fail, parseErrorMessage, parseErrorPosition, position, region, runParser)
import Text.Parsing.Parser.Combinators (between, chainl, chainl1Rec, chainlRec, chainr1Rec, chainrRec, endBy1, endBy1Rec, endByRec, many1Rec, many1TillRec, many1TillRec_, many1Till_, manyTillRec, manyTillRec_, manyTill_, notFollowedBy, optionMaybe, sepBy1, sepBy1Rec, sepByRec, sepEndBy1Rec, sepEndByRec, skipMany1Rec, skipManyRec, try, (<?>), (<~?>), (<??>))
import Text.Parsing.Parser.Combinators (between, chainl, chainl1Rec, chainlRec, chainr1Rec, chainrRec, choice, endBy1, endBy1Rec, endByRec, many1Rec, many1TillRec, many1TillRec_, many1Till_, manyTillRec, manyTillRec_, manyTill_, notFollowedBy, optionMaybe, sepBy1, sepBy1Rec, sepByRec, sepEndBy1Rec, sepEndByRec, skipMany1Rec, skipManyRec, try, (<?>), (<??>), (<~?>))
import Text.Parsing.Parser.Expr (Assoc(..), Operator(..), buildExprParser)
import Text.Parsing.Parser.Language (haskellDef, haskellStyle, javaStyle)
import Text.Parsing.Parser.Pos (Position(..), initialPos)
Expand Down Expand Up @@ -727,6 +727,16 @@ main = do
"no"
"No alternative"

-- Choice shouldn't always yield "No alternative", that's what `oneOf` is for.
parseErrorTestMessage
( choice
[ string "a"
, string "b"
]
)
"c"
"Expected \"b\""

-- we can't test "NaN" with `parseTest` because nan doesn't compare equal
case runParser "NaN" number of
Right actual -> do
Expand Down