From 8a89e76966aeb8067fe1369d4da0721bee0b4e9c Mon Sep 17 00:00:00 2001
From: David Jablonski <dayjaby@gmail.com>
Date: Sat, 29 Jan 2022 14:14:55 +0100
Subject: [PATCH 1/2] protoc_gen_mavsdk: error on missing return value

When defining a rpc function with a return stream, it is necessary that
this function returns something that is not a *Result. So the Response
proto must contain more than just the result entry. Here we give an
explicit error message, so that the developer knows precisely what is
missing.
---
 pb_plugins/protoc_gen_mavsdk/methods.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/pb_plugins/protoc_gen_mavsdk/methods.py b/pb_plugins/protoc_gen_mavsdk/methods.py
index 46c73ddf2..130206dbb 100644
--- a/pb_plugins/protoc_gen_mavsdk/methods.py
+++ b/pb_plugins/protoc_gen_mavsdk/methods.py
@@ -74,6 +74,10 @@ def extract_return_type_and_name(self, pb_method, responses):
             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(
+                "Responses 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,

From 4bc0d91f2257dc14f1299c7bce0af8b96cece73d Mon Sep 17 00:00:00 2001
From: David Jablonski <dayjaby@gmail.com>
Date: Sat, 29 Jan 2022 14:23:05 +0100
Subject: [PATCH 2/2] improved wording

---
 pb_plugins/protoc_gen_mavsdk/methods.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pb_plugins/protoc_gen_mavsdk/methods.py b/pb_plugins/protoc_gen_mavsdk/methods.py
index 130206dbb..16c9111dc 100644
--- a/pb_plugins/protoc_gen_mavsdk/methods.py
+++ b/pb_plugins/protoc_gen_mavsdk/methods.py
@@ -66,7 +66,7 @@ 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(
@@ -76,8 +76,8 @@ def extract_return_type_and_name(self, pb_method, responses):
             self._return_description = return_params[0]['docs']
         elif len(return_params) == 0 and self.return_type_required:
             raise Exception(
-                "Responses must have 1 return parameter" +
-                f"(and an optional '*Result')!\nError in {method_output}")
+                "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