Function _parse_braces

src/borg/helpers/shellpattern.py:71–105

Return the index pairs of matched braces in `pat` as a list of tuples. The dictionary's keys are the indices corresponding to opening braces. Initially, they are set to a value of `None`. Once a corresponding closing brace is found, the value is updated. All dictionary keys with a posit

(pat)

def _parse_braces(pat):
    """Return the index pairs of matched braces in `pat` as a list of tuples.

    The dictionary's keys are the indices corresponding to opening braces. Initially,
    they are set to a value of `None`. Once a corresponding closing brace is found,
    the value is updated. All dictionary keys with a positive integer value are valid pairs.

    We cannot rely on re.match("[^\\(\\\\)*]?{.*[^\\(\\\\)*]}") because, while it
    handles unpaired braces and nested pairs of braces, it misses sequences
    of paired braces. For example: "{foo,bar}{bar,baz}" would translate, incorrectly, to
    "(foo|bar\\}\\{bar|baz)" instead of, correctly, to "(foo|bar)(bar|baz)".

    Therefore, this function parses left-to-right, tracking pairs with a LIFO
    queue: pushing opening braces on and popping them off when finding a closing
    brace.
    """
    curly_q = LifoQueue()
    pairs: dict[int, int] = dict()

    for idx, c in enumerate(pat):
        if c == "{":
            if idx == 0 or pat[idx - 1] != "\\":
                # Opening brace is not escaped.
                # Add to dict
                pairs[idx] = None
                # Add to queue
                curly_q.put(idx)
        if c == "}" and curly_q.qsize():
            # If queue is empty, then cannot close pair.
            if idx > 0 and pat[idx - 1] != "\\":
                # Closing brace is not escaped.
                # Pop off the index of the corresponding opening brace, which
                # provides the key in the dict of pairs, and set its value.
                pairs[curly_q.get()] = idx
    return [(opening, closing) for opening, closing in pairs.items() if closing is not None]


def _translate_alternatives(pat):