fix: ensure exception is available when BackgroundConsumer open stream fails

Author: parthea

google/api_core/bidi.py

@@ -276,7 +276,11 @@ def open(self):
         request_generator = _RequestQueueGenerator(
             self._request_queue, initial_request=self._initial_request
         )
-        call = self._start_rpc(iter(request_generator), metadata=self._rpc_metadata)
+        try:
+            call = self._start_rpc(iter(request_generator), metadata=self._rpc_metadata)
+        except exceptions.GoogleAPICallError as exc:
+            self._on_call_done(exc)
+            raise
 
         request_generator.call = call
 

tests/unit/test_bidi.py

@@ -804,6 +804,20 @@ def test_wake_on_error(self):
         while consumer.is_active:
             pass
 
+    def test_rpc_callback_fires_when_consumer_start_fails(self):
+        expected_exception = exceptions.InvalidArgument("test")
+        callback = mock.Mock(spec=["__call__"])
+        rpc, _ = make_rpc()
+        bidi_rpc = bidi.BidiRpc(rpc)
+        bidi_rpc.add_done_callback(callback)
+        bidi_rpc._start_rpc.side_effect = expected_exception
+
+        consumer = bidi.BackgroundConsumer(bidi_rpc, on_response=lambda: None)
+
+        consumer.start()
+
+        assert callback.call_args.args[0] == expected_exception
+
     def test_consumer_expected_error(self, caplog):
         caplog.set_level(logging.DEBUG)