openapi gen return type fix for streaming/non-streaming

docs/openapi_generator/pyopenapi/generator.py

@@ -177,20 +177,37 @@ def build_content(
     ) -> Dict[str, MediaType]:
         "Creates the content subtree for a request or response."
 
-        def has_iterator_type(t):
-            if typing.get_origin(t) is typing.Union:
-                return any(has_iterator_type(a) for a in typing.get_args(t))
+        def is_iterator_type(t):
+            return "StreamChunk" in str(t)
+
+        def get_media_type(t):
+            if is_generic_list(t):
+                return "application/jsonl"
+            elif is_iterator_type(t):
+                return "text/event-stream"
             else:
-                # TODO: needs a proper fix where we let all types correctly flow upwards
-                # and then test against AsyncIterator
-                return "StreamChunk" in str(t)
+                return "application/json"
+
+        if typing.get_origin(payload_type) is typing.Union:
+            media_types = []
+            item_types = []
+            for x in typing.get_args(payload_type):
+                media_types.append(get_media_type(x))
+                item_types.append(x)
+
+            if len(set(media_types)) == 1:
+                # all types have the same media type
+                return {media_types[0]: self.build_media_type(payload_type, examples)}
+            else:
+                # different types have different media types
+                return {
+                    media_type: self.build_media_type(item_type, examples)
+                    for media_type, item_type in zip(media_types, item_types)
+                }
 
         if is_generic_list(payload_type):
             media_type = "application/jsonl"
             item_type = unwrap_generic_list(payload_type)
-        elif has_iterator_type(payload_type):
-            item_type = payload_type
-            media_type = "text/event-stream"
         else:
             media_type = "application/json"
             item_type = payload_type