Merge c1d19462f95000f3a7b3edcb9555a2fc44b694f9 into a2bee2f255853c6e019e1651a168c12dff64d68f

Don't send the fields `avatar_url` and `displayname` when
they are not defined for the queried user.

Before this change they would be sent and set to null in the JSON response object,
which would violate the OpenAPI definitions
(c.f. https://spec.matrix.org/v1.11/server-server-api/#get_matrixfederationv1queryprofile).

changelog.d/18593.bugfix

@@ -0,0 +1 @@
+Fix avatar_url and displayname being sent on profile queries when they are null.

synapse/handlers/profile.py

@@ -539,11 +539,17 @@ class ProfileHandler:
         response: JsonDict = {}
         try:
             if just_field is None or just_field == ProfileFields.DISPLAYNAME:
-                response["displayname"] = await self.store.get_profile_displayname(user)
-
+                displayname = await self.store.get_profile_displayname(user)
+                # do not set the displayname field if it is None,
+                # since then we send a null in the JSON response
+                if displayname is not None:
+                    response["displayname"] = displayname
             if just_field is None or just_field == ProfileFields.AVATAR_URL:
-                response["avatar_url"] = await self.store.get_profile_avatar_url(user)
-
+                avatar_url = await self.store.get_profile_avatar_url(user)
+                # do not set the avatar_url field if it is None,
+                # since then we send a null in the JSON response
+                if avatar_url is not None:
+                    response["avatar_url"] = avatar_url
             if self.hs.config.experimental.msc4133_enabled:
                 if just_field is None:
                     response.update(await self.store.get_profile_fields(user))