chore: Add a2a task result aggregator

PiperOrigin-RevId: 775975982

Author: seanzhougoogle

src/google/adk/a2a/executor/__init__.py

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+# Copyright 2025 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.

src/google/adk/a2a/executor/task_result_aggregator.py

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+# Copyright 2025 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 __future__ import annotations
+
+from a2a.server.events import Event
+from a2a.types import Message
+from a2a.types import TaskState
+from a2a.types import TaskStatusUpdateEvent
+
+from ...utils.feature_decorator import working_in_progress
+
+
+@working_in_progress
+class TaskResultAggregator:
+  """Aggregates the task status updates and provides the final task state."""
+
+  def __init__(self):
+    self._task_state = TaskState.working
+    self._task_status_message = None
+
+  def process_event(self, event: Event):
+    """Process an event from the agent run and detect signals about the task status.
+    Priority of task state:
+    - failed
+    - auth_required
+    - input_required
+    - working
+    """
+    if isinstance(event, TaskStatusUpdateEvent):
+      if event.status.state == TaskState.failed:
+        self._task_state = TaskState.failed
+        self._task_status_message = event.status.message
+      elif (
+          event.status.state == TaskState.auth_required
+          and self._task_state != TaskState.failed
+      ):
+        self._task_state = TaskState.auth_required
+        self._task_status_message = event.status.message
+      elif (
+          event.status.state == TaskState.input_required
+          and self._task_state
+          not in (TaskState.failed, TaskState.auth_required)
+      ):
+        self._task_state = TaskState.input_required
+        self._task_status_message = event.status.message
+      # final state is already recorded and make sure the intermediate state is
+      # always working because other state may terminate the event aggregation
+      # in a2a request handler
+      elif self._task_state == TaskState.working:
+        self._task_status_message = event.status.message
+      event.status.state = TaskState.working
+
+  @property
+  def task_state(self) -> TaskState:
+    return self._task_state
+
+  @property
+  def task_status_message(self) -> Message | None:
+    return self._task_status_message

tests/unittests/a2a/executor/__init__.py

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+# Copyright 2025 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.