"global flags not at the start of the expression" error when using in-line global regex flag with Python 11+

[BobbyRBruce]

We have this in our code:

    def t_STRLIT(self, t):
        r'(?m)"([^"])*"'
        # strip off quotes
        t.value = t.value[1:-1]
        t.lexer.lineno += t.value.count('\n')
        return t

This code works fine for Python versions <11. With Python 11, however, we get the following error:

Invalid regular expression for rule 't_STRLIT'. global flags not at the start of the expression at position 13
SyntaxError: Can't build lexer

As of Python 11 you cannot put an in-line global regex flag anywhere but the start of an expression (e.g., (?m) in this case must be at the start of the regex expression). We require (?m) in this expression so MULTILINE is enabled for it. The issue manifests in this line in lex.py's validate_rules function:

c = re.compile('(?P<%s>%s)' % (fname, _get_regex(f)), self.reflags)

As can be seen, the appending of the regex string after ?P<%s> is problematic (the (?m) is now not at the start of the expression).

I cannot find a good solution to this problem. I'm aware I can set the regex flags for lex (via the reflags parameter), but it is my understanding these are apply to all expressions. I require the flags to be set on a per-expression basis (i.e., t_STRLIT should have MULTILINE enabled, but no others).

[dabeaz]

I don't have any advice on fixing this problem other than a change to the regex itself.