/brz/remove-bazaar

# Copyright (C) 2006, 2008-2011, 2017 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Lazily compiled regex objects.

This module defines a class which creates proxy objects for regex

compilation.  This allows overriding re.compile() to return lazily compiled

objects.

We do this rather than just providing a new interface so that it will also

be used by existing Python modules that create regexs.

"""

import re

from . import errors

class InvalidPattern(errors.BzrError):

    _fmt = ('Invalid pattern(s) found. %(msg)s')

    def __init__(self, msg):

        self.msg = msg

class LazyRegex(object):

    """A proxy around a real regex, which won't be compiled until accessed."""

    # These are the parameters on a real _sre.SRE_Pattern object, which we

    # will map to local members so that we don't have the proxy overhead.

    _regex_attributes_to_copy = [

        '__copy__', '__deepcopy__', 'findall', 'finditer', 'match',

        'scanner', 'search', 'split', 'sub', 'subn'

        ]

    # We use slots to keep the overhead low. But we need a slot entry for

    # all of the attributes we will copy

    __slots__ = ['_real_regex', '_regex_args', '_regex_kwargs',

                 ] + _regex_attributes_to_copy

    def __init__(self, args, kwargs):

        """Create a new proxy object, passing in the args to pass to re.compile

        :param args: The `*args` to pass to re.compile

        :param kwargs: The `**kwargs` to pass to re.compile

        """

        self._real_regex = None

        self._regex_args = args

        self._regex_kwargs = kwargs

    def _compile_and_collapse(self):

        """Actually compile the requested regex"""

        self._real_regex = self._real_re_compile(*self._regex_args,

                                                 **self._regex_kwargs)

        for attr in self._regex_attributes_to_copy:

            setattr(self, attr, getattr(self._real_regex, attr))

    def _real_re_compile(self, *args, **kwargs):

        """Thunk over to the original re.compile"""

        try:

            return re.compile(*args, **kwargs)

        except re.error as e:

            # raise InvalidPattern instead of re.error as this gives a

            # cleaner message to the user.

            raise InvalidPattern('"' + args[0] + '" ' + str(e))

    def __getstate__(self):

        """Return the state to use when pickling."""

        return {

            "args": self._regex_args,

            "kwargs": self._regex_kwargs,

            }

    def __setstate__(self, dict):

        """Restore from a pickled state."""

        self._real_regex = None

        setattr(self, "_regex_args", dict["args"])

        setattr(self, "_regex_kwargs", dict["kwargs"])

    def __getattr__(self, attr):

        """Return a member from the proxied regex object.

        If the regex hasn't been compiled yet, compile it

        """

        if self._real_regex is None:

            self._compile_and_collapse()

        # Once we have compiled, the only time we should come here

        # is actually if the attribute is missing.

        return getattr(self._real_regex, attr)

def lazy_compile(*args, **kwargs):

    """Create a proxy object which will compile the regex on demand.

    :return: a LazyRegex proxy object.

    """

    return LazyRegex(args, kwargs)