fix: patch emulator channel to be created accordingly (#288)

Co-authored-by: Christopher Wilcox <crwilcox@google.com>

google/cloud/firestore_v1/base_client.py

@@ -148,7 +148,7 @@ def _firestore_api_helper(self, transport, client_class, client_module) -> Any:
             # We need this in order to set appropriate keepalive options.
 
             if self._emulator_host is not None:
-                channel = self._emulator_channel()
+                channel = self._emulator_channel(transport)
             else:
                 channel = transport.create_channel(
                     self._target,
@@ -165,25 +165,30 @@ def _firestore_api_helper(self, transport, client_class, client_module) -> Any:
 
         return self._firestore_api_internal
 
-    def _emulator_channel(self):
+    def _emulator_channel(self, transport):
         """
         Creates a channel using self._credentials in a similar way to grpc.secure_channel but
         using grpc.local_channel_credentials() rather than grpc.ssh_channel_credentials() to allow easy connection
         to a local firestore emulator. This allows local testing of firestore rules if the credentials have been
         created from a signed custom token.
 
-        :return: grcp.Channel
+        :return: grpc.Channel or grpc.aio.Channel
         """
-        return grpc._channel.Channel(
-            self._emulator_host,
-            (),
-            self._local_composite_credentials()._credentials,
-            None,
-        )
+        # TODO: Implement a special credentials type for emulator and use
+        # "transport.create_channel" to create gRPC channels once google-auth
+        # extends it's allowed credentials types.
+        if "GrpcAsyncIOTransport" in str(transport.__name__):
+            return grpc.aio.secure_channel(
+                self._emulator_host, self._local_composite_credentials()
+            )
+        else:
+            return grpc.secure_channel(
+                self._emulator_host, self._local_composite_credentials()
+            )
 
     def _local_composite_credentials(self):
         """
-        Ceates the credentials for the local emulator channel
+        Creates the credentials for the local emulator channel
         :return: grpc.ChannelCredentials
         """
         credentials = google.auth.credentials.with_scopes_if_required(

tests/unit/v1/test_base_client.py

@@ -138,6 +138,13 @@ def test__rpc_metadata_property_with_emulator(self):
         )
 
     def test_emulator_channel(self):
+        from google.cloud.firestore_v1.services.firestore.transports.grpc import (
+            FirestoreGrpcTransport,
+        )
+        from google.cloud.firestore_v1.services.firestore.transports.grpc_asyncio import (
+            FirestoreGrpcAsyncIOTransport,
+        )
+
         emulator_host = "localhost:8081"
         with mock.patch("os.getenv") as getenv:
             getenv.return_value = emulator_host
@@ -149,8 +156,10 @@ def test_emulator_channel(self):
             )
 
         # checks that a channel is created
-        channel = client._emulator_channel()
-        self.assertTrue(isinstance(channel, grpc._channel.Channel))
+        channel = client._emulator_channel(FirestoreGrpcTransport)
+        self.assertTrue(isinstance(channel, grpc.Channel))
+        channel = client._emulator_channel(FirestoreGrpcAsyncIOTransport)
+        self.assertTrue(isinstance(channel, grpc.aio.Channel))
         # checks that the credentials are composite ones using a local channel from grpc
         composite_credentials = client._local_composite_credentials()
         self.assertTrue(isinstance(composite_credentials, grpc.ChannelCredentials))