Merge pull request #273 from dayjaby/error-missing-return-value

protoc_gen_mavsdk: error on missing return value

pb_plugins/protoc_gen_mavsdk/methods.py

@@ -66,14 +66,18 @@ def extract_return_type_and_name(self, pb_method, responses):
         if len(return_params) > 1:
             raise Exception(
                 "Responses cannot have more than 1 return parameter" +
-                f"(and an optional '*Result')!\nError in {method_output}")
+                f" (and an optional '*Result')!\nError in {method_output}")
 
         if len(return_params) == 1:
             self._return_type = type_info_factory.create(
                 return_params[0]['field'])
             self._return_name = name_parser_factory.create(
                 return_params[0]['field'].json_name)
             self._return_description = return_params[0]['docs']
+        elif len(return_params) == 0 and self.return_type_required:
+            raise Exception(
+                "This response must have 1 return parameter" +
+                f" (and an optional '*Result')!\nError in {method_output}")
 
     def extract_async_type(self, pb_method):
         self._is_sync = True
@@ -119,6 +123,10 @@ def package(self):
     def name(self):
         return self._name
 
+    @property
+    def return_type_required(self):
+        return False
+
     @staticmethod
     def collect_methods(
             plugin_name,
@@ -270,6 +278,10 @@ def __init__(
             remove_subscribe(pb_method.name))
         self._template = template_env.get_template("stream.j2")
 
+    @property
+    def return_type_required(self):
+        return True
+
     def __repr__(self):
         return self._template.render(
             name=self._name,