/
require_started.py
35 lines (28 loc) · 1.12 KB
/
require_started.py
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# Copyright 2020 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.
from typing import ContextManager
from google.api_core.exceptions import FailedPrecondition
class RequireStarted(ContextManager):
def __init__(self):
self._started = False
def __enter__(self):
if self._started:
raise FailedPrecondition("__enter__ called twice.")
self._started = True
return self
def require_started(self):
if not self._started:
raise FailedPrecondition("__enter__ has never been called.")
def __exit__(self, exc_type, exc_value, traceback):
self.require_started()