[feat] RPCs that return Empty should return None.

gapic/schema/metadata.py

@@ -58,6 +58,11 @@ def __str__(self) -> str:
         Because we import modules as a whole, rather than individual
         members from modules, this is consistently `module.Name`.
         """
+        # Edge case: For google.protobuf.Empty, use None instead.
+        if self.proto == 'google.protobuf.Empty':
+            return 'None'
+
+        # Most (but not all) types are in a module.
         if self.module:
             # If collisions are registered and conflict with our module,
             # use the module alias instead.

gapic/schema/wrappers.py

@@ -415,7 +415,9 @@ def grpc_stub_type(self) -> str:
     def ref_types(self) -> Sequence[Union[MessageType, EnumType]]:
         """Return types referenced by this method."""
         # Begin with the input (request) and output (response) messages.
-        answer = [self.input, self.output]
+        answer = [self.input]
+        if not self.void:
+            answer.append(self.output)
 
         # If this method has flattening that is honored, add its
         # composite types.
@@ -458,6 +460,11 @@ def signatures(self) -> 'MethodSignatures':
         # Done; return a tuple of signatures.
         return MethodSignatures(all=tuple(answer))
 
+    @property
+    def void(self) -> bool:
+        """Return True if this method has no return value, False otherwise."""
+        return self.output.ident.proto == 'google.protobuf.Empty'
+
     def with_context(self, *, collisions: Set[str]) -> 'Method':
         """Return a derivative of this method with the provided context.
 

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

@@ -70,10 +70,12 @@ class {{ service.name }}:
             timeout (float): The timeout for this request.
             metadata (Sequence[Tuple[str, str]]): Strings which should be
                 sent along with the request as metadata.
+        {%- if not method.void %}
 
         Returns:
             {{ method.output.ident.sphinx }}:
                 {{ method.output.meta.doc|wrap(width=72, indent=16) }}
+        {%- endif %}
         """
         # Wrap the RPC method; this adds retry and timeout information,
         # and friendly error handling.
@@ -97,8 +99,12 @@ class {{ service.name }}:
         {%- endif %}
 
         # Send the request.
-        response = rpc(request, retry=retry,
-                       timeout=timeout, metadata=metadata)
+        {% if not method.void %}response = {% endif %}rpc(
+            request,
+            retry=retry,
+            timeout=timeout,
+            metadata=metadata,
+        )
         {%- if method.output.lro_response is defined %}
 
         # Wrap the response in an operation future
@@ -111,9 +117,11 @@ class {{ service.name }}:
             {%- endif %}
         )
         {%- endif %}
+        {%- if not method.void %}
 
         # Done; return the response.
         return response
+        {%- endif %}
 
     {% for signature in method.signatures.single_dispatch -%}
     @{{ method.name|snake_case }}.register
@@ -138,10 +146,12 @@ class {{ service.name }}:
             timeout (float): The timeout for this request.
             metadata (Sequence[Tuple[str, str]]): Strings which should be
                 sent alont with the request as metadata.
+        {%- if not method.void %}
 
         Returns:
             {{ method.output.ident.sphinx }}:
                 {{ method.output.meta.doc|wrap(width=72, indent=16) }}
+        {%- endif %}
         """
         return self.{{ method.name|snake_case }}(
             {{ method.input.ident }}(
@@ -158,7 +168,8 @@ class {{ service.name }}:
 
     @classmethod
     def get_transport_class(cls,
-            label: str = None) -> Type[{{ service.name }}Transport]:
+            label: str = None,
+            ) -> Type[{{ service.name }}Transport]:
         """Return an appropriate transport class.
 
         Args:

gapic/templates/$namespace/$name_$version/$sub/services/$service/transports/grpc.py.j2

@@ -111,8 +111,9 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
 
         Returns:
             Callable[[~.{{ method.input.name }}],
-                    ~.{{ method.output.name }}]:
-                {{ method.output.meta.doc|rst(width=72, indent=16) }}
+                    {% if method.void %}None{% else %}~.{{ method.output.name }}{% endif %}]:
+                A function that, when called, will call the underlying RPC
+                on the server.
         """
         # Generate a "stub function" on-the-fly which will actually make
         # the request.
@@ -121,8 +122,8 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
         if '{{ method.name|snake_case }}' not in self._stubs:
             self._stubs['{{ method.name|snake_case }}'] = self.grpc_channel.{{ method.grpc_stub_type }}(
                 '/{{ '.'.join(method.meta.address.package) }}.{{ service.name }}/{{ method.name }}',
-                request_serializer={{ method.input.ident }}.serialize,
-                response_deserializer={{ method.output.ident }}.deserialize,
+                request_serializer={{ method.input.ident }}.{% if method.input.ident.module.endswith('_pb2') %}SerializeToString{% else %}serialize{% endif %},
+                response_deserializer={{ method.output.ident }}.{% if method.input.ident.module.endswith('_pb2') %}FromString{% else %}deserialize{% endif %},
             )
         return self._stubs['{{ method.name|snake_case }}']
     {%- endfor %}

gapic/templates/$namespace/$name_$version/$sub/services/$service/transports/http.py.j2

@@ -81,17 +81,23 @@ class {{ service.name }}HttpTransport({{ service.name }}Transport):
                 The request object.
                 {{ method.input.meta.doc|rst(width=72, indent=16) }}
             metadata (Sequence[Tuple[str, str]]): Strings which should be
-                sent alont with the request as metadata.
+                sent along with the request as metadata.
+        {%- if not method.void %}
 
         Returns:
             ~.{{ method.output.ident }}:
                 {{ method.output.meta.doc|rst(width=72, indent=16) }}
+        {%- endif %}
         """
         # Serialize the input.
+        {%- if method.input.ident.module.endswith('_pb2') %}
         data = request.SerializeToString()
+        {%- else %}
+        data = {{ method.input.ident }}.serialize(request)
+        {%- endif %}
 
         # Send the request.
-        response = self._session.post(
+        {% if not method.void %}response = {% endif %}self._session.post(
             'https://{host}/$rpc/{package}.{service}/{method}'.format(
                 host=self._host,
                 method='{{ method.name }}',
@@ -103,11 +109,13 @@ class {{ service.name }}HttpTransport({{ service.name }}Transport):
                 'content-type': 'application/x-protobuf',
             },
         )
+        {%- if not method.void %}
 
         # Return the response.
-        return {{ method.output.ident }}.FromString(
+        return {{ method.output.ident }}.{% if method.input.ident.module.endswith('_pb2') %}FromString{% else %}deserialize{% endif %}(
             response.content,
         )
+        {%- endif %}
     {%- endfor %}
 
 

tests/unit/schema/test_metadata.py

@@ -40,6 +40,15 @@ def test_address_str_parent():
     assert str(addr) == 'baz.spam.eggs.Bacon'
 
 
+def test_address_str_empty():
+    addr = metadata.Address(
+        package=('google', 'protobuf'),
+        module='empty_pb2',
+        name='Empty',
+    )
+    assert str(addr) == 'None'
+
+
 def test_address_proto():
     addr = metadata.Address(package=('foo', 'bar'), module='baz', name='Bacon')
     assert addr.proto == 'foo.bar.Bacon'

tests/unit/schema/wrappers/test_method.py

@@ -88,6 +88,18 @@ def test_method_no_signature():
     assert len(make_method('Ping').signatures) == 0
 
 
+def test_method_void():
+    empty = make_message(name='Empty', package='google.protobuf')
+    method = make_method('Meh', output_message=empty)
+    assert method.void
+
+
+def test_method_not_void():
+    not_empty = make_message(name='OutputMessage', package='foo.bar.v1')
+    method = make_method('Meh', output_message=not_empty)
+    assert not method.void
+
+
 def test_method_field_headers_none():
     method = make_method('DoSomething')
     assert isinstance(method.field_headers, collections.Sequence)