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visit_all_entities_and_collect_futures_impl.py
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visit_all_entities_and_collect_futures_impl.py
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# Copyright 2018 Open Source Robotics Foundation, Inc.
#
# 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.
"""Module for the visit_all_entities_and_collect_futures() utility function."""
import asyncio
from typing import List
from typing import Tuple
from ..launch_context import LaunchContext
from ..launch_description_entity import LaunchDescriptionEntity
def visit_all_entities_and_collect_futures(
entity: LaunchDescriptionEntity,
context: LaunchContext
) -> List[Tuple[LaunchDescriptionEntity, asyncio.Future]]:
"""
Visit given entity, as well as all sub-entities, and collect any futures.
Sub-entities are visited recursively and depth-first.
The future is collected from each entity (unless it returns None) before
continuing on to more sub-entities.
This function may call itself to traverse the sub-entities recursively.
"""
sub_entities = entity.visit(context)
entity_future = entity.get_asyncio_future()
futures_to_return = []
if entity_future is not None:
futures_to_return.append((entity, entity_future))
if sub_entities is not None:
for sub_entity in sub_entities:
futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
return [future_pair for future_pair in futures_to_return if future_pair[1] is not None]