Remove dependency on pcre-light

[rehno-lindeque]

Pcre-light is a bit of an annoyance when deploying code since it requires carrying along libpcre. It's only used in one place:

http://github.com/bos/mysql-simple/blob/e0c79e6c8a6874709565cca6de6c6ce6d1dcc8ce/Database/MySQL/Simple.hs#L165

I'm hoping to replace that regular expression with an attoparsec parser so that we can drop the dependency. Would that make sense @bos?

[rehno-lindeque]

I'm having a little trouble understanding the first group ([^?]+\bvalues\s*) in the regex though (my perl is a bit novice). I've implemented this as skipWhile1 (/= '?') *> take 1 *> stringCI "values" *> skipSpace in attoparsec, but I'm almost sure this must be wrong - I'm not sure how to parse [^?]+\b correctly. I'd be grateful for any help!

For reference here's the full regex

re = compile "^([^?]+\\bvalues\\s*)\
              \(\\(\\s*[?](?:\\s*,\\s*[?])*\\s*\\))\
              \([^?]*)$"
      [caseless]

and my attoparsec implementation

skipWhile1 f = satisfy f *> skipWhile f

parser :: Parser (ByteString, ByteString, ByteString)
parser = do
  -- Skip VALUES keyword
  skipWhile1 (/= '?') *> take 1 *> stringCI "values" *> skipSpace
  -- Take (...?
  before <- char '(' *> takeTill (== '?')
  -- Skip ?,?,?,...
  skipMany (skipSpace *> char ',' *> skipSpace *> char '?')
  -- Take )
  qbits <- takeWhile (== ' ') <* char ')'
  after <- takeWhile (/= '?')
  endOfInput
  return ('(' `cons` before, qbits `snoc` ')', after)

does that look ok?

[dvzrv]

@paul-rouse hi! :wave:

I'm packaging pcre2 for Arch Linux and we are currently working on moving from pcre (now unmaintained) to pcre2. Would it be possible to prioritize the removal of pcre or alternatively to switch to e.g. https://github.com/sjshuck/hs-pcre2?