fix: resolve AttributeError by supporting both Pydantic and Protobuf AgentCard serialization

noxfile.py

@@ -110,6 +110,7 @@
     "unit_agentplatform_langchain",
     "unit_agentplatform_ag2",
     "unit_agentplatform_llama_index",
+    "unit_agentplatform_a2a",
     "system",
     "cover",
     "lint",
@@ -222,6 +223,7 @@ def default(session):
         "--ignore=tests/unit/vertex_langchain",
         "--ignore=tests/unit/vertex_ag2",
         "--ignore=tests/unit/vertex_llama_index",
+        "--ignore=tests/unit/vertex_a2a",
         "--ignore=tests/unit/architecture",
         "--ignore=tests/unit/vertexai/genai/replays",
         "--ignore=tests/unit/agentplatform/genai/replays",
@@ -311,6 +313,9 @@ def unit_agentplatform_adk(session):
     # Install adk extras
     session.install("-e", ".[adk_testing]", "-c", constraints_path)
 
+    a2a_constraints = str(CURRENT_DIRECTORY / "testing" / "constraints-a2a.txt")
+    session.install("a2a-sdk", "-c", a2a_constraints)
+
     # Run py.test against the unit tests.
     session.run(
         "py.test",
@@ -324,6 +329,7 @@ def unit_agentplatform_adk(session):
         os.path.join(
             "tests", "unit", "agentplatform", "frameworks", "test_frameworks_adk.py"
         ),
+        os.path.join("tests", "unit", "vertex_a2a"),
         *session.posargs,
     )
 
@@ -429,6 +435,29 @@ def unit_agentplatform_llama_index(session):
     )
 
 
+@nox.session(python=["3.14"])
+def unit_agentplatform_a2a(session):
+    # Install all test dependencies, then install this package in-place.
+
+    constraints_path = str(CURRENT_DIRECTORY / "testing" / "constraints-a2a.txt")
+    install_unittest_dependencies(session, "-c", constraints_path)
+    session.install("a2a-sdk", "-c", constraints_path)
+
+    # Run py.test against the unit tests.
+    session.run(
+        "py.test",
+        "--quiet",
+        "--junitxml=unit_agentplatform_a2a_sponge_log.xml",
+        "--cov=google",
+        "--cov-append",
+        "--cov-config=.coveragerc",
+        "--cov-report=",
+        "--cov-fail-under=0",
+        os.path.join("tests", "unit", "vertex_a2a"),
+        *session.posargs,
+    )
+
+
 @nox.session(python=UNIT_TEST_TEMPLATES_PYTHON_VERSIONS)
 def unit_langchain(session):
     # Install all test dependencies, then install this package in-place.

testing/constraints-a2a.txt

@@ -0,0 +1,2 @@
+protobuf>=5.29.5
+a2a-sdk>=1.0.0

tests/unit/vertex_a2a/test_agent_engines_a2a.py

@@ -0,0 +1,314 @@
+# Copyright 2026 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 os
+import sys
+import tempfile
+from unittest import mock
+import pytest
+import cloudpickle
+import pydantic
+
+from google import auth
+from google.api_core import operation as ga_operation
+from google.auth import credentials as auth_credentials
+from google.cloud import storage
+from google.cloud import aiplatform
+from google.cloud.aiplatform import base
+
+from google.cloud.aiplatform_v1 import types
+from google.cloud.aiplatform_v1.services import reasoning_engine_service
+from vertexai import agent_engines
+from vertexai.agent_engines import _agent_engines
+from vertexai.agent_engines import _utils
+from google.protobuf import struct_pb2
+
+
+class CapitalizeEngine:
+    """A sample Agent Engine."""
+
+    def query(self, unused_arbitrary_string_name: str) -> str:
+        """Runs the engine."""
+        return unused_arbitrary_string_name.upper()
+
+
+class CapitalizeEngineWithCard(CapitalizeEngine):
+
+    def __init__(self, card):
+        self.agent_card = card
+
+    def __getstate__(self):
+        state = self.__dict__.copy()
+        if hasattr(self.agent_card, "DESCRIPTOR"):
+            state["agent_card"] = None
+        return state
+
+    def __setstate__(self, state):
+        self.__dict__.update(state)
+
+
+class DummyPydanticCard(pydantic.BaseModel):
+    name: str = "test_pydantic_card"
+
+
+def _create_empty_fake_package(package_name: str) -> str:
+    temp_dir = tempfile.mkdtemp()
+    package_dir = os.path.join(temp_dir, package_name)
+    os.makedirs(package_dir)
+    init_path = os.path.join(package_dir, "__init__.py")
+    open(init_path, "w").close()
+    return temp_dir
+
+
+_TEST_CREDENTIALS = mock.Mock(spec=auth_credentials.AnonymousCredentials())
+_TEST_STAGING_BUCKET = "gs://test-bucket"
+_TEST_LOCATION = "us-central1"
+_TEST_PROJECT = "test-project"
+_TEST_RESOURCE_ID = "1028944691210842416"
+_TEST_PARENT = f"projects/{_TEST_PROJECT}/locations/{_TEST_LOCATION}"
+_TEST_AGENT_ENGINE_RESOURCE_NAME = (
+    f"{_TEST_PARENT}/reasoningEngines/{_TEST_RESOURCE_ID}"
+)
+_TEST_AGENT_ENGINE_DISPLAY_NAME = "Agent Engine Display Name"
+_TEST_GCS_DIR_NAME = _agent_engines._DEFAULT_GCS_DIR_NAME
+_TEST_BLOB_FILENAME = _agent_engines._BLOB_FILENAME
+_TEST_REQUIREMENTS_FILE = _agent_engines._REQUIREMENTS_FILE
+_TEST_EXTRA_PACKAGES_FILE = _agent_engines._EXTRA_PACKAGES_FILE
+_TEST_STANDARD_API_MODE = _agent_engines._STANDARD_API_MODE
+_TEST_DEFAULT_METHOD_NAME = _agent_engines._DEFAULT_METHOD_NAME
+_TEST_MODE_KEY_IN_SCHEMA = _agent_engines._MODE_KEY_IN_SCHEMA
+
+_TEST_AGENT_ENGINE_EXTRA_PACKAGE = "fake.py"
+
+_TEST_AGENT_ENGINE_EXTRA_PACKAGE_PATH = _create_empty_fake_package(
+    _TEST_AGENT_ENGINE_EXTRA_PACKAGE
+)
+
+_TEST_AGENT_ENGINE_REQUIREMENTS = [
+    "google-cloud-aiplatform==1.29.0",
+    "langchain",
+]
+
+_TEST_AGENT_ENGINE_GCS_URI = "{}/{}/{}".format(
+    _TEST_STAGING_BUCKET,
+    _TEST_GCS_DIR_NAME,
+    _TEST_BLOB_FILENAME,
+)
+_TEST_AGENT_ENGINE_DEPENDENCY_FILES_GCS_URI = "{}/{}/{}".format(
+    _TEST_STAGING_BUCKET,
+    _TEST_GCS_DIR_NAME,
+    _TEST_EXTRA_PACKAGES_FILE,
+)
+_TEST_AGENT_ENGINE_REQUIREMENTS_GCS_URI = "{}/{}/{}".format(
+    _TEST_STAGING_BUCKET,
+    _TEST_GCS_DIR_NAME,
+    _TEST_REQUIREMENTS_FILE,
+)
+
+_TEST_AGENT_ENGINE_QUERY_SCHEMA = _utils.to_proto(
+    _utils.generate_schema(
+        CapitalizeEngine().query,
+        schema_name=_TEST_DEFAULT_METHOD_NAME,
+    )
+)
+_TEST_AGENT_ENGINE_QUERY_SCHEMA[_TEST_MODE_KEY_IN_SCHEMA] = _TEST_STANDARD_API_MODE
+
+_TEST_AGENT_ENGINE_PACKAGE_SPEC = types.ReasoningEngineSpec.PackageSpec(
+    python_version=f"{sys.version_info.major}.{sys.version_info.minor}",
+    pickle_object_gcs_uri=_TEST_AGENT_ENGINE_GCS_URI,
+    dependency_files_gcs_uri=_TEST_AGENT_ENGINE_DEPENDENCY_FILES_GCS_URI,
+    requirements_gcs_uri=_TEST_AGENT_ENGINE_REQUIREMENTS_GCS_URI,
+)
+
+_TEST_AGENT_ENGINE_OBJ = types.ReasoningEngine(
+    name=_TEST_AGENT_ENGINE_RESOURCE_NAME,
+    spec=types.ReasoningEngineSpec(
+        package_spec=_TEST_AGENT_ENGINE_PACKAGE_SPEC,
+        agent_framework=_agent_engines._DEFAULT_AGENT_FRAMEWORK,
+    ),
+)
+_TEST_AGENT_ENGINE_OBJ.spec.class_methods.append(_TEST_AGENT_ENGINE_QUERY_SCHEMA)
+
+
+@pytest.fixture(scope="module")
+def google_auth_mock():
+    with mock.patch.object(auth, "default") as google_auth_mock:
+        google_auth_mock.return_value = (
+            auth_credentials.AnonymousCredentials(),
+            _TEST_PROJECT,
+        )
+        yield google_auth_mock
+
+
+@pytest.fixture(scope="module")
+def cloud_storage_create_bucket_mock():
+    with mock.patch.object(storage, "Client") as cloud_storage_mock:
+        bucket_mock = mock.Mock(spec=storage.Bucket)
+        bucket_mock.blob.return_value.open.return_value = "blob_file"
+        bucket_mock.blob.return_value.upload_from_filename.return_value = None
+        bucket_mock.blob.return_value.upload_from_string.return_value = None
+
+        cloud_storage_mock.get_bucket = mock.Mock(
+            side_effect=ValueError("bucket not found")
+        )
+        cloud_storage_mock.bucket.return_value = bucket_mock
+        cloud_storage_mock.create_bucket.return_value = bucket_mock
+
+        yield cloud_storage_mock
+
+
+@pytest.fixture(scope="module")
+def cloudpickle_load_mock():
+    with mock.patch.object(cloudpickle, "load") as cloudpickle_load_mock:
+        yield cloudpickle_load_mock
+
+
+@pytest.fixture(scope="module")
+def create_agent_engine_mock():
+    with mock.patch.object(
+        reasoning_engine_service.ReasoningEngineServiceClient,
+        "create_reasoning_engine",
+    ) as create_agent_engine_mock:
+        create_agent_engine_lro_mock = mock.Mock(spec=ga_operation.Operation)
+        create_agent_engine_lro_mock.result.return_value = _TEST_AGENT_ENGINE_OBJ
+        create_agent_engine_mock.return_value = create_agent_engine_lro_mock
+        yield create_agent_engine_mock
+
+
+@pytest.fixture(scope="function")
+def get_gca_resource_mock():
+    with mock.patch.object(
+        base.VertexAiResourceNoun,
+        "_get_gca_resource",
+    ) as get_gca_resource_mock:
+        get_gca_resource_mock.return_value = _TEST_AGENT_ENGINE_OBJ
+        yield get_gca_resource_mock
+
+
+@pytest.mark.usefixtures("google_auth_mock")
+class TestAgentEngineA2A:
+    def setup_method(self):
+        aiplatform.init(
+            project=_TEST_PROJECT,
+            location=_TEST_LOCATION,
+            credentials=_TEST_CREDENTIALS,
+            staging_bucket=_TEST_STAGING_BUCKET,
+        )
+
+    def test_create_agent_engine_with_protobuf_agent_card(
+        self,
+        create_agent_engine_mock,
+        cloud_storage_create_bucket_mock,
+        cloudpickle_load_mock,
+        get_gca_resource_mock,
+    ):
+        a2a_pb2 = None
+        # fmt: off
+        try:
+            try:
+                from a2a.compat.v0_3 import a2a_v0_3_pb2 as a2a_pb2
+            except ImportError:
+                from a2a.grpc import a2a_pb2
+            has_a2a_pb2 = True
+        except (ImportError, TypeError):
+            has_a2a_pb2 = False
+        # fmt: on
+
+        if not has_a2a_pb2:
+            pytest.skip("a2a_pb2 could not be imported.")
+
+        card = a2a_pb2.AgentCard(name="test_agent_card")
+        agent = CapitalizeEngineWithCard(card)
+
+        agent_engines.create(
+            agent,
+            display_name=_TEST_AGENT_ENGINE_DISPLAY_NAME,
+            requirements=_TEST_AGENT_ENGINE_REQUIREMENTS,
+            extra_packages=[_TEST_AGENT_ENGINE_EXTRA_PACKAGE_PATH],
+        )
+
+        expected_reasoning_engine = types.ReasoningEngine(
+            display_name=_TEST_AGENT_ENGINE_DISPLAY_NAME,
+            spec=types.ReasoningEngineSpec(
+                package_spec=_TEST_AGENT_ENGINE_PACKAGE_SPEC,
+                agent_framework=_agent_engines._DEFAULT_AGENT_FRAMEWORK,
+            ),
+        )
+        from google.protobuf import json_format
+
+        expected_class_method = struct_pb2.Struct()
+        expected_class_method.CopyFrom(_TEST_AGENT_ENGINE_QUERY_SCHEMA)
+        expected_class_method["a2a_agent_card"] = json_format.MessageToJson(card)
+        expected_reasoning_engine.spec.class_methods.append(expected_class_method)
+
+        create_agent_engine_mock.assert_called_with(
+            parent=_TEST_PARENT,
+            reasoning_engine=expected_reasoning_engine,
+        )
+
+    def test_create_agent_engine_with_pydantic_agent_card(
+        self,
+        create_agent_engine_mock,
+        cloud_storage_create_bucket_mock,
+        cloudpickle_load_mock,
+        get_gca_resource_mock,
+    ):
+        card = DummyPydanticCard()
+        agent = CapitalizeEngineWithCard(card)
+
+        agent_engines.create(
+            agent,
+            display_name=_TEST_AGENT_ENGINE_DISPLAY_NAME,
+            requirements=_TEST_AGENT_ENGINE_REQUIREMENTS,
+            extra_packages=[_TEST_AGENT_ENGINE_EXTRA_PACKAGE_PATH],
+        )
+
+        expected_reasoning_engine = types.ReasoningEngine(
+            display_name=_TEST_AGENT_ENGINE_DISPLAY_NAME,
+            spec=types.ReasoningEngineSpec(
+                package_spec=_TEST_AGENT_ENGINE_PACKAGE_SPEC,
+                agent_framework=_agent_engines._DEFAULT_AGENT_FRAMEWORK,
+            ),
+        )
+
+        expected_class_method = struct_pb2.Struct()
+        expected_class_method.CopyFrom(_TEST_AGENT_ENGINE_QUERY_SCHEMA)
+        expected_class_method["a2a_agent_card"] = card.model_dump_json()
+        expected_reasoning_engine.spec.class_methods.append(expected_class_method)
+
+        create_agent_engine_mock.assert_called_with(
+            parent=_TEST_PARENT,
+            reasoning_engine=expected_reasoning_engine,
+        )
+
+    def test_create_agent_engine_with_invalid_agent_card(
+        self,
+        create_agent_engine_mock,
+        cloud_storage_create_bucket_mock,
+        cloudpickle_load_mock,
+        get_gca_resource_mock,
+    ):
+        agent = CapitalizeEngineWithCard(card="invalid_card_type_string")
+
+        with pytest.raises(
+            TypeError,
+            match="Unsupported AgentCard type",
+        ):
+            agent_engines.create(
+                agent,
+                display_name=_TEST_AGENT_ENGINE_DISPLAY_NAME,
+                requirements=_TEST_AGENT_ENGINE_REQUIREMENTS,
+                extra_packages=[_TEST_AGENT_ENGINE_EXTRA_PACKAGE_PATH],
+            )