Add simpleParsecBS and use it in scanSpecVersion

Cabal/Distribution/PackageDescription/Parsec.hs

@@ -54,7 +54,7 @@ import Distribution.PackageDescription
 import Distribution.PackageDescription.Configuration (freeVars)
 import Distribution.PackageDescription.FieldGrammar
 import Distribution.PackageDescription.Quirks        (patchQuirks)
-import Distribution.Parsec                           (parsec, simpleParsec)
+import Distribution.Parsec                           (parsec, simpleParsecBS)
 import Distribution.Parsec.FieldLineStream           (fieldLineStreamFromBS)
 import Distribution.Parsec.Newtypes                  (CommaFSep, List, SpecVersion (..), Token)
 import Distribution.Parsec.Position                  (Position (..), zeroPos)
@@ -859,7 +859,7 @@ scanSpecVersion bs = do
     --
     -- This is currently more tolerant regarding leading 0 digits.
     --
-    ver <- simpleParsec (BS8.unpack vers)
+    ver <- simpleParsecBS vers
     guard $ case versionNumbers ver of
               [_,_]   -> True
               [_,_,_] -> True

Cabal/Distribution/Parsec.hs

@@ -10,6 +10,7 @@ module Distribution.Parsec (
     runParsecParser,
     runParsecParser',
     simpleParsec,
+    simpleParsecBS,
     simpleParsec',
     simpleParsecW',
     lexemeParsec,
@@ -50,7 +51,8 @@ import Data.List                           (transpose)
 import Distribution.CabalSpecVersion
 import Distribution.Compat.Prelude
 import Distribution.Parsec.Error           (PError (..), showPError)
-import Distribution.Parsec.FieldLineStream (FieldLineStream, fieldLineStreamFromString)
+import Data.ByteString (ByteString)
+import Distribution.Parsec.FieldLineStream (FieldLineStream, fieldLineStreamFromString, fieldLineStreamFromBS)
 import Distribution.Parsec.Position        (Position (..), incPos, retPos, showPos, zeroPos)
 import Distribution.Parsec.Warning         (PWarnType (..), PWarning (..), showPWarning)
 import Numeric                             (showIntAtBase)
@@ -176,6 +178,13 @@ simpleParsec
     . runParsecParser lexemeParsec "<simpleParsec>"
     . fieldLineStreamFromString
 
+-- | Like 'simpleParsec' but for 'ByteString'
+simpleParsecBS :: Parsec a => ByteString -> Maybe a
+simpleParsecBS
+    = either (const Nothing) Just
+    . runParsecParser lexemeParsec "<simpleParsec>"
+    . fieldLineStreamFromBS
+
 -- | Parse a 'String' with 'lexemeParsec' using specific 'CabalSpecVersion'.
 --
 -- @since 3.4.0.0