contrib/check-py3-compat.py

patch: handle filenames with trailing spaces

I have no idea if this is *actually* supported by the patch file format, but at
least when reading from a patch file created by running `hg shelve`, it is
written out such that there's a trailing space after the second (`b`) filename.
When we read the patch file, we remove the space before parsing the filenames,
so it doesn't end up matching the other sources of what files are in the shelve.

We observed this internally due to a wrapper around unshelve that called into
patch.changedfiles, but `hg patch` is able to reproduce the issue as well, so
I've included both tests.

Differential Revision: https://phab.mercurial-scm.org/D9729

#!/usr/bin/env python3
#
# 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 importlib
import os
import sys
import traceback
import warnings


def check_compat_py2(f):
    """Check Python 3 compatibility for a file with Python 2"""
    with open(f, 'rb') as fh:
        content = fh.read()
    root = ast.parse(content)

    # Ignore empty files.
    if not root.body:
        return

    futures = set()
    haveprint = False
    for node in ast.walk(root):
        if isinstance(node, ast.ImportFrom):
            if node.module == '__future__':
                futures |= {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)


def check_compat_py3(f):
    """Check Python 3 compatibility of a file with Python 3."""
    with open(f, 'rb') as fh:
        content = fh.read()

    try:
        ast.parse(content, filename=f)
    except SyntaxError as e:
        print('%s: invalid syntax: %s' % (f, e))
        return

    # Try to import the module.
    # For now we only support modules in packages because figuring out module
    # paths for things not in a package can be confusing.
    if f.startswith(
        ('hgdemandimport/', 'hgext/', 'mercurial/')
    ) and not f.endswith('__init__.py'):
        assert f.endswith('.py')
        name = f.replace('/', '.')[:-3]
        try:
            importlib.import_module(name)
        except Exception as e:
            exc_type, exc_value, tb = sys.exc_info()
            # We walk the stack and ignore frames from our custom importer,
            # import mechanisms, and stdlib modules. This kinda/sorta
            # emulates CPython behavior in import.c while also attempting
            # to pin blame on a Mercurial file.
            for frame in reversed(traceback.extract_tb(tb)):
                if frame.name == '_call_with_frames_removed':
                    continue
                if 'importlib' in frame.filename:
                    continue
                if 'mercurial/__init__.py' in frame.filename:
                    continue
                if frame.filename.startswith(sys.prefix):
                    continue
                break

            if frame.filename:
                filename = os.path.basename(frame.filename)
                print(
                    '%s: error importing: <%s> %s (error at %s:%d)'
                    % (f, type(e).__name__, e, filename, frame.lineno)
                )
            else:
                print(
                    '%s: error importing module: <%s> %s (line %d)'
                    % (f, type(e).__name__, e, frame.lineno)
                )


if __name__ == '__main__':
    if sys.version_info[0] == 2:
        fn = check_compat_py2
    else:
        # check_compat_py3 will import every filename we specify as long as it
        # starts with one of a few prefixes. It does this by converting
        # specified filenames like 'mercurial/foo.py' to 'mercurial.foo' and
        # importing that. When running standalone (not as part of a test), this
        # means we actually import the installed versions, not the files we just
        # specified. When running as test-check-py3-compat.t, we technically
        # would import the correct paths, but it's cleaner to have both cases
        # use the same import logic.
        sys.path.insert(0, '.')
        fn = check_compat_py3

    for f in sys.argv[1:]:
        with warnings.catch_warnings(record=True) as warns:
            fn(f)

        for w in warns:
            print(
                warnings.formatwarning(
                    w.message, w.category, w.filename, w.lineno
                ).rstrip()
            )

    sys.exit(0)