contrib/check-py3-compat.py

revset: infer ordering flag to teach if operation should define/follow order

New flag 'order' is the hint to determine if a function or operation can
enforce its ordering requirement or take the ordering already defined. It
will be used to fix a couple of ordering bugs, such as:

 a) 'x & (y | z)' disregards the order of 'x' (issue5100)
 b) 'x & y:z' is listed from 'y' to 'z'
 c) 'x & y' can be rewritten as 'y & x' if weight(x) > weight(y)

(a) and (b) are bugs of the revset core. Before this, there was no way to
tell if 'orset()' and 'rangeset()' can enforce its ordering. These bugs
could be addressed by overriding __and__() of the initial set to take the
ordering of the other set:

    class fullreposet:
        def __and__(self, other):
            # allow other to enforce its ordering
            return other

but it would expose (c), which is a hidden bug of optimize(). So, in either
ways, optimize() have to know the current ordering requirement. Otherwise,
it couldn't rewrite expressions by weights with no output change, nor tell
how a revset function or operation should order the entries.

'order' is tri-state. It starts with 'define', and shifts to 'follow' by
'x & y'. It changes back to 'define' on function call 'f(x)' or function-like
operation 'x (f) y' because 'f' may have its own ordering requirement for 'x'
and 'y'. The state 'any' will allow us to avoid extra cost that would be
necessary to constrain ordering where it isn't important, 'not x'.

#!/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 imp
import os
import sys
import traceback

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 |= 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)

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)
    except SyntaxError as e:
        print('%s: invalid syntax: %s' % (f, e))
        return

    # Try to import the module.
    # For now we only support mercurial.* and hgext.* modules because figuring
    # out module paths for things not in a package can be confusing.
    if f.startswith(('hgext/', 'mercurial/')) and not f.endswith('__init__.py'):
        assert f.endswith('.py')
        name = f.replace('/', '.')[:-3].replace('.pure.', '.')
        with open(f, 'r') as fh:
            try:
                imp.load_module(name, fh, '', ('py', 'r', imp.PY_SOURCE))
            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:
        fn = check_compat_py3

    for f in sys.argv[1:]:
        fn(f)

    sys.exit(0)