contrib/check-py3-compat.py

destutil: choose non-closed branch head at first (BC)

Before this patch, destupdate() returns the tipmost (descendant)
branch head regardless of closed or not. But updating to closed branch
head isn't reasonable for ordinary workflow, because:

  - "hg heads" doesn't show closed heads (= updated parent itself) by
    default

  - subsequent committing on it re-opens closed branch

    even if inactivation of closed head is needed, update destination
    isn't it, because it should be merged into to another branch in
    such case.

This patch chooses non-closed descendant branch head as default update
destination at first. If all descendant branch heads are closed,
destupdate() returns the tipmost closed branch head.

For simplicity, this patch chooses adding _destupdatebranchfallback()
instead largely changing _destupdatebranch().

This patch changes not only normal lookup code path, but also the "no
default branch" code path, for consistency.

#!/usr/bin/env python
#
# check-py3-compat - check Python 3 compatibility of Mercurial files
#
# Copyright 2015 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import, print_function

import ast
import sys

def check_compat(f):
    """Check Python 3 compatibility for a file."""
    with open(f, 'rb') as fh:
        content = fh.read()

    # Ignore empty files.
    if not content.strip():
        return

    root = ast.parse(content)
    futures = set()
    haveprint = False
    for node in ast.walk(root):
        if isinstance(node, ast.ImportFrom):
            if node.module == '__future__':
                futures |= set(n.name for n in node.names)
        elif isinstance(node, ast.Print):
            haveprint = True

    if 'absolute_import' not in futures:
        print('%s not using absolute_import' % f)
    if haveprint and 'print_function' not in futures:
        print('%s requires print_function' % f)

if __name__ == '__main__':
    for f in sys.argv[1:]:
        check_compat(f)

    sys.exit(0)