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[EDIT] FILE: demand.py

# demand.py
# Demand sheet and related classes.
#
# Copyright (C) 2014-2015  Red Hat, Inc.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions of
# the GNU General Public License v.2, or (at your option) any later version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY expressed or implied, including the implied warranties 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.  Any Red Hat trademarks that are incorporated in the
# source code or documentation are not subject to the GNU General Public
# License and may only be used or replicated with the express permission of
# Red Hat, Inc.
#

from __future__ import unicode_literals

class _BoolDefault(object):
    def __init__(self, default):
        self.default = default
        self._storing_name = '__%s%x' % (self.__class__.__name__, id(self))

def __get__(self, obj, objtype=None):
        objdict = obj.__dict__
        if self._storing_name in objdict:
            return objdict[self._storing_name]
        return self.default

def __set__(self, obj, val):
        objdict = obj.__dict__
        if self._storing_name in objdict:
            current_val = objdict[self._storing_name]
            if current_val != val:
                raise AttributeError('Demand already set.')
        objdict[self._storing_name] = val

class DemandSheet(object):
    """Collection of demands that different CLI parts have on other parts. :api"""

# :api...
    allow_erasing = _BoolDefault(False)
    available_repos = _BoolDefault(False)
    resolving = _BoolDefault(False)
    root_user = _BoolDefault(False)
    sack_activation = _BoolDefault(False)
    load_system_repo = _BoolDefault(True)
    success_exit_status = 0

cacheonly = _BoolDefault(False)
    fresh_metadata = _BoolDefault(True)
    freshest_metadata = _BoolDefault(False)
    changelogs = _BoolDefault(False)

transaction_display = None

# This demand controlls applicability of the plugins that could filter
    # repositories packages (e.g. versionlock).
    # If it stays None, the demands.resolving is used as a fallback.
    plugin_filtering_enabled = _BoolDefault(None)

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