fix: remove duplicate field entries (#786)

Fix for #778

gapic/templates/%namespace/%name_%version/%sub/services/%service/client.py.j2

@@ -365,7 +365,7 @@ class {{ service.client_name }}(metaclass={{ service.client_name }}Meta):
             request = {{ method.input.ident }}(**request)
         {% if method.flattened_fields -%}{# Cross-package req and flattened fields #}
         elif not request:
-            request = {{ method.input.ident }}({% if method.input.ident.package != method.ident.package %}{% for f in method.flattened_fields.values() %}{{ f.name }}={{ f.name }}, {% endfor %}{% endif %})
+            request = {{ method.input.ident }}()
         {% endif -%}{# Cross-package req and flattened fields #}
         {%- else %}
         # Minor optimization to avoid making a copy if the user passes

gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2

@@ -471,6 +471,30 @@ def test_{{ method.name|snake_case }}_from_dict():
     test_{{ method.name|snake_case }}(request_type=dict)
 
 
+{% if not method.client_streaming -%}
+def test_{{ method.name|snake_case }}_empty_call():
+    # This test is a coverage failsafe to make sure that totally empty calls,
+    # i.e. request == None and no flattened fields passed, work.
+    client = {{ service.client_name }}(
+        credentials=credentials.AnonymousCredentials(),
+        transport='grpc',
+    )
+
+    # Mock the actual call within the gRPC stub, and fake the request.
+    with mock.patch.object(
+            type(client.transport.{{ method.name|snake_case }}),
+            '__call__') as call:
+        client.{{ method.name|snake_case }}()
+        call.assert_called()
+        _, args, _ = call.mock_calls[0]
+        {% if method.client_streaming %}
+        assert next(args[0]) == request
+        {% else %}
+        assert args[0] == {{ method.input.ident }}()
+        {% endif %}
+{% endif -%}
+
+
 @pytest.mark.asyncio
 async def test_{{ method.name|snake_case }}_async(transport: str = 'grpc_asyncio', request_type={{ method.input.ident }}):
     client = {{ service.async_client_name }}(
@@ -1276,7 +1300,7 @@ def test_{{ method.name|snake_case }}_pager():
         for result in results:
             assert isinstance(result, tuple)
             assert tuple(type(t) for t in result) == (str, {{ method.paged_result_field.type.fields.get('value').ident }})
-        
+
         assert pager.get('a') is None
         assert isinstance(pager.get('h'), {{ method.paged_result_field.type.fields.get('value').ident }})
         {% else %}
@@ -1288,7 +1312,7 @@ def test_{{ method.name|snake_case }}_pager():
         for page_, token in zip(pages, ['abc','def','ghi', '']):
             assert page_.raw_page.next_page_token == token
 
-        
+
 {% endif %} {# paged methods #}
 {% endfor -%} {#- method in methods for rest #}
 def test_credentials_transport_error():
@@ -1500,7 +1524,7 @@ def test_{{ service.name|snake_case }}_grpc_transport_client_cert_source_for_mtl
                 ("grpc.max_receive_message_length", -1),
             ],
         )
-        
+
     # Check if ssl_channel_credentials is not provided, then client_cert_source_for_mtls
     # is used.
     with mock.patch.object(transport_class, "create_channel", return_value=mock.Mock()):