[WIP]fix: validate transport types in ConfigClient and ConfigAsyncClient

packages/google-cloud-config/google/cloud/config_v1/services/config/async_client.py

@@ -60,7 +60,9 @@
 
 from .client import ConfigClient
 from .transports.base import DEFAULT_CLIENT_INFO, ConfigTransport
+from .transports.grpc import ConfigGrpcTransport
 from .transports.grpc_asyncio import ConfigGrpcAsyncIOTransport
+from .transports.rest import ConfigRestTransport
 
 try:
     from google.api_core import client_logging  # type: ignore
@@ -284,11 +286,25 @@ def __init__(
             google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
                 creation failed for any reason.
         """
+        transport_provided = isinstance(transport, ConfigTransport)
+
+        if (
+            transport_provided
+            and isinstance(transport, (ConfigGrpcTransport, ConfigRestTransport))
+        ) or (
+            isinstance(transport, str) and transport in ["grpc", "rest"]
+        ):
+            raise ValueError(
+                "The `ConfigAsyncClient` does not support sync transports. "
+                "Please use `ConfigClient` instead."
+            )
+
         self._client = ConfigClient(
             credentials=credentials,
             transport=transport,
             client_options=client_options,
             client_info=client_info,
+            _allow_async_transport=True,
         )
 
         if CLIENT_LOGGING_SUPPORTED and _LOGGER.isEnabledFor(

packages/google-cloud-config/google/cloud/config_v1/services/config/client.py

@@ -779,6 +779,7 @@ def __init__(
         ] = None,
         client_options: Optional[Union[client_options_lib.ClientOptions, dict]] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        _allow_async_transport: bool = False,
     ) -> None:
         """Instantiates the config client.
 
@@ -870,6 +871,18 @@ def __init__(
         # Ordinarily, we provide the transport, but allowing a custom transport
         # instance provides an extensibility point for unusual situations.
         transport_provided = isinstance(transport, ConfigTransport)
+
+        # Raise an exception if the async transport is provided.
+        if (
+            not _allow_async_transport
+            and transport_provided
+            and isinstance(transport, ConfigGrpcAsyncIOTransport)
+        ):
+            raise ValueError(
+                "The `ConfigClient` does not support async transports. "
+                "Please use `ConfigAsyncClient` instead."
+            )
+
         if transport_provided:
             # transport is a ConfigTransport instance.
             if credentials or self._client_options.credentials_file or api_key_value:
@@ -909,6 +922,18 @@ def __init__(
                 if isinstance(transport, str) or transport is None
                 else cast(Callable[..., ConfigTransport], transport)
             )
+
+            # Raise an exception if the async transport is provided.
+            if (
+                not _allow_async_transport
+                and isinstance(transport, str)
+                and transport == "grpc_asyncio"
+            ):
+                raise ValueError(
+                    "The `ConfigClient` does not support async transports. "
+                    "Please use `ConfigAsyncClient` instead."
+                )
+
             # initialize with the provided callable or the passed in class
             self._transport = transport_init(
                 credentials=credentials,

packages/google-cloud-config/tests/unit/gapic/config_v1/test_client_validation.py

@@ -0,0 +1,79 @@
+# -*- coding: utf-8 -*-
+# 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.
+#
+import pytest
+from unittest import mock
+from google.cloud.config_v1 import ConfigClient, ConfigAsyncClient
+from google.cloud.config_v1.services.config import transports
+from google.auth import credentials as ga_credentials
+
+def test_config_client_validates_grpc_asyncio_string():
+    creds = ga_credentials.AnonymousCredentials()
+    with pytest.raises(ValueError) as excinfo:
+        ConfigClient(credentials=creds, transport="grpc_asyncio")
+    assert "ConfigClient" in str(excinfo.value)
+    assert "async transports" in str(excinfo.value)
+
+def test_config_client_validates_grpc_asyncio_object():
+    creds = ga_credentials.AnonymousCredentials()
+    transport = transports.ConfigGrpcAsyncIOTransport(credentials=creds)
+    with pytest.raises(ValueError) as excinfo:
+        ConfigClient(transport=transport)
+    assert "ConfigClient" in str(excinfo.value)
+    assert "async transports" in str(excinfo.value)
+
+def test_config_client_allows_custom_transport():
+    creds = ga_credentials.AnonymousCredentials()
+    class CustomTransport(transports.ConfigTransport):
+        pass
+    transport = CustomTransport(credentials=creds)
+    # Should not raise
+    ConfigClient(transport=transport)
+
+def test_config_async_client_validates_grpc_string():
+    creds = ga_credentials.AnonymousCredentials()
+    with pytest.raises(ValueError) as excinfo:
+        ConfigAsyncClient(credentials=creds, transport="grpc")
+    assert "ConfigAsyncClient" in str(excinfo.value)
+    assert "sync transports" in str(excinfo.value)
+
+def test_config_async_client_validates_rest_string():
+    creds = ga_credentials.AnonymousCredentials()
+    with pytest.raises(ValueError) as excinfo:
+        ConfigAsyncClient(credentials=creds, transport="rest")
+    assert "ConfigAsyncClient" in str(excinfo.value)
+    assert "sync transports" in str(excinfo.value)
+
+def test_config_async_client_validates_grpc_object():
+    creds = ga_credentials.AnonymousCredentials()
+    transport = transports.ConfigGrpcTransport(credentials=creds)
+    with pytest.raises(ValueError) as excinfo:
+        ConfigAsyncClient(transport=transport)
+    assert "ConfigAsyncClient" in str(excinfo.value)
+    assert "sync transports" in str(excinfo.value)
+
+def test_config_async_client_allows_custom_transport():
+    creds = ga_credentials.AnonymousCredentials()
+    class CustomTransport(transports.ConfigTransport):
+        pass
+    transport = CustomTransport(credentials=creds)
+    # Should not raise
+    ConfigAsyncClient(transport=transport)
+
+def test_config_async_client_initialization_happy_path():
+    creds = ga_credentials.AnonymousCredentials()
+    # Should not raise
+    client = ConfigAsyncClient(credentials=creds)
+    assert isinstance(client._client, ConfigClient)

packages/google-cloud-config/tests/unit/gapic/config_v1/test_config.py

@@ -25421,7 +25421,6 @@ def test_config_http_transport_client_cert_source_for_mtls():
     "transport_name",
     [
         "grpc",
-        "grpc_asyncio",
         "rest",
     ],
 )
@@ -25444,7 +25443,6 @@ def test_config_host_no_port(transport_name):
     "transport_name",
     [
         "grpc",
-        "grpc_asyncio",
         "rest",
     ],
 )