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imports.py
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imports.py
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# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import builtins
from unittest import mock
def maybe_fail_import(predicate):
"""Create and return a patcher that conditionally makes an import fail.
Args:
predicate (Callable[[...], bool]): A callable that, if it returns `True`,
triggers an `ImportError`. It must accept the same arguments as the
built-in `__import__` function.
https://docs.python.org/3/library/functions.html#__import__
Returns:
A mock patcher object that can be used to enable patched import behavior.
"""
orig_import = builtins.__import__
def custom_import(name, globals=None, locals=None, fromlist=(), level=0):
if predicate(name, globals, locals, fromlist, level):
raise ImportError
return orig_import(name, globals, locals, fromlist, level)
return mock.patch.object(builtins, "__import__", new=custom_import)