hgext/fsmonitor/pywatchman/capabilities.py

bdiff: add version to help detect breaking binary changes

Previously, we have no way to detect if a compiled .so file could be used or
not, and blindly load it if it exists. Usually we carefully maintain
compatibility of .so and fallback to pure code gracefully. But if we stick
to the rules, certain nice changes will be impossible to make in a clean
way.

This patch adds a "version" constant to the module so we can detect
inconsistency and take appropriate actions (warn, abort, fallback to pure,
run make automatically) in module loader.

# Copyright 2015 Facebook, Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#  * Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
#
#  * Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
#
#  * Neither the name Facebook nor the names of its contributors may be used to
#    endorse or promote products derived from this software without specific
#    prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
# no unicode literals

import re

def parse_version(vstr):
    res = 0
    for n in vstr.split('.'):
        res = res * 1000
        res = res + int(n)
    return res

cap_versions = {
    "cmd-watch-del-all": "3.1.1",
    "cmd-watch-project": "3.1",
    "relative_root": "3.3",
    "term-dirname": "3.1",
    "term-idirname": "3.1",
    "wildmatch": "3.7",
}

def check(version, name):
    if name in cap_versions:
        return version >= parse_version(cap_versions[name])
    return False

def synthesize(vers, opts):
    """ Synthesize a capability enabled version response
        This is a very limited emulation for relatively recent feature sets
    """
    parsed_version = parse_version(vers['version'])
    vers['capabilities'] = {}
    for name in opts['optional']:
        vers['capabilities'][name] = check(parsed_version, name)
    failed = False
    for name in opts['required']:
        have = check(parsed_version, name)
        vers['capabilities'][name] = have
        if not have:
            vers['error'] = 'client required capability `' + name + \
                            '` is not supported by this server'
    return vers