# This file is part of Hypothesis, which may be found at
# Most of this work is copyright (C) 2013-2020 David R. MacIver
# (firstname.lastname@example.org), but it contains contributions by others. See
# CONTRIBUTING.rst for a full list of people who may hold copyright, and
# consult the git log if you need to determine who owns an individual
# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
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This module provides tools for working with the :pypi:`dpcontracts` library,
because `combining contracts and property-based testing works really well
It requires ``dpcontracts >= 0.4``.
from dpcontracts import PreconditionError
from hypothesis import reject
from hypothesis.errors import InvalidArgument
from hypothesis.internal.reflection import proxies
"""Decorate ``contract_func`` to reject calls which violate preconditions,
and retry them with different arguments.
This is a convenience function for testing internal code that uses
:pypi:`dpcontracts`, to automatically filter out arguments that would be
rejected by the public interface before triggering a contract error.
This can be used as ``builds(fulfill(func), ...)`` or in the body of the
test e.g. ``assert fulfill(func)(*args)``.
if not hasattr(contract_func, "__contract_wrapped_func__"):
"There are no dpcontracts preconditions associated with %s"
def inner(*args, **kwargs):
return contract_func(*args, **kwargs)