fix: get channel target for a gRPC request (#1339)

tests/unit/pubsub_v1/publisher/test_publisher_client.py

@@ -57,6 +57,14 @@
 typed_flaky = cast(Callable[[C], C], flaky(max_runs=5, min_passes=1))
 
 
+# NOTE: This interceptor is required to create an intercept channel.
+class _PublisherClientGrpcInterceptor(
+    grpc.UnaryUnaryClientInterceptor,
+):
+    def intercept_unary_unary(self, continuation, client_call_details, request):
+        pass
+
+
 def _assert_retries_equal(retry, retry2):
     # Retry instances cannot be directly compared, because their predicates are
     # different instances of the same function. We thus manually compare their other
@@ -416,17 +424,27 @@ def init(self, *args, **kwargs):
         assert client.transport._ssl_channel_credentials == mock_ssl_creds
 
 
-def test_init_emulator(monkeypatch):
+def test_init_emulator(monkeypatch, creds):
     monkeypatch.setenv("PUBSUB_EMULATOR_HOST", "/foo/bar:123")
     # NOTE: When the emulator host is set, a custom channel will be used, so
     #       no credentials (mock ot otherwise) can be passed in.
-    client = publisher.Client()
+
+    # TODO(https://github.com/grpc/grpc/issues/38519): Workaround to create an intercept
+    # channel (for forwards compatibility) with a channel created by the publisher client
+    # where target is set to the emulator host.
+    channel = publisher.Client().transport.grpc_channel
+    interceptor = _PublisherClientGrpcInterceptor()
+    intercept_channel = grpc.intercept_channel(channel, interceptor)
+    transport = publisher.Client.get_transport_class("grpc")(
+        credentials=creds, channel=intercept_channel
+    )
+    client = publisher.Client(transport=transport)
 
     # Establish that a gRPC request would attempt to hit the emulator host.
     #
     # Sadly, there seems to be no good way to do this without poking at
     # the private API of gRPC.
-    channel = client._transport.publish._channel
+    channel = client._transport.publish._thunk("")._channel
     # Behavior to include dns prefix changed in gRPCv1.63
     grpc_major, grpc_minor = [int(part) for part in grpc.__version__.split(".")[0:2]]
     if grpc_major > 1 or (grpc_major == 1 and grpc_minor >= 63):

tests/unit/pubsub_v1/subscriber/test_subscriber_client.py

@@ -36,6 +36,14 @@
 from google.pubsub_v1.types import PubsubMessage
 
 
+# NOTE: This interceptor is required to create an intercept channel.
+class _SubscriberClientGrpcInterceptor(
+    grpc.UnaryUnaryClientInterceptor,
+):
+    def intercept_unary_unary(self, continuation, client_call_details, request):
+        pass
+
+
 def test_init_default_client_info(creds):
     client = subscriber.Client(credentials=creds)
 
@@ -119,17 +127,27 @@ def init(self, *args, **kwargs):
         assert client.transport._ssl_channel_credentials == mock_ssl_creds
 
 
-def test_init_emulator(monkeypatch):
+def test_init_emulator(monkeypatch, creds):
     monkeypatch.setenv("PUBSUB_EMULATOR_HOST", "/baz/bacon:123")
     # NOTE: When the emulator host is set, a custom channel will be used, so
     #       no credentials (mock ot otherwise) can be passed in.
-    client = subscriber.Client()
+
+    # TODO(https://github.com/grpc/grpc/issues/38519): Workaround to create an intercept
+    # channel (for forwards compatibility) with a channel created by the publisher client
+    # where target is set to the emulator host.
+    channel = subscriber.Client().transport.grpc_channel
+    interceptor = _SubscriberClientGrpcInterceptor()
+    intercept_channel = grpc.intercept_channel(channel, interceptor)
+    transport = subscriber.Client.get_transport_class("grpc")(
+        credentials=creds, channel=intercept_channel
+    )
+    client = subscriber.Client(transport=transport)
 
     # Establish that a gRPC request would attempt to hit the emulator host.
     #
     # Sadly, there seems to be no good way to do this without poking at
     # the private API of gRPC.
-    channel = client._transport.pull._channel
+    channel = client._transport.pull._thunk("")._channel
     # Behavior to include dns prefix changed in gRPCv1.63
     grpc_major, grpc_minor = [int(part) for part in grpc.__version__.split(".")[0:2]]
     if grpc_major > 1 or (grpc_major == 1 and grpc_minor >= 63):