fix: show staff tag for global staff in discussion forum

lms/djangoapps/discussion/rest_api/api.py

@@ -2419,6 +2419,14 @@ def get_user_label(user_id):
                 return "Moderator"
             elif user_id_int in ta_user_ids:
                 return "Community TA"
+            else:
+                # Check if user is a platform-wide staff member
+                try:
+                    user = User.objects.get(id=user_id_int)
+                    if user.is_staff:
+                        return "Staff"
+                except User.DoesNotExist:
+                    pass
         except (ValueError, TypeError):
             # If user_id has any issues, there's no label to return
             pass

lms/djangoapps/discussion/rest_api/serializers.py

@@ -277,6 +277,14 @@ def _get_user_label(self, user_id):
         is_moderator = user_id in self.context["moderator_user_ids"]
         is_ta = user_id in self.context["ta_user_ids"]
 
+        # Check if user is a platform-wide staff member
+        if not is_staff:
+            try:
+                user = User.objects.get(id=user_id)
+                is_staff = user.is_staff
+            except ObjectDoesNotExist:
+                pass
+
         return (
             "Staff"
             if is_staff

lms/djangoapps/discussion/rest_api/tests/test_serializers.py

@@ -151,6 +151,30 @@ def test_author_labels(self, role_name, anonymous, expected_label):
         serialized = self.serialize(self.make_cs_content({"anonymous": anonymous}))
         assert serialized["author_label"] == expected_label
 
+    @ddt.data(
+        (False, "Staff"),
+        (True, None),
+    )
+    @ddt.unpack
+    def test_author_label_for_global_staff(self, anonymous, expected_label):
+        """
+        Test that platform-wide staff members get the "Staff" label.
+
+        Users with is_staff=True should receive the "Staff" label even if they
+        don't have a course-specific role, unless the content is anonymous.
+
+        anonymous is the value of the anonymous field in the content.
+        expected_label is the expected value of the author_label field in the
+          API output.
+        """
+        # Make author a platform-wide staff member
+        self.author.is_staff = True
+        self.author.save()
+
+        # Don't assign any forum role - author should still get "Staff" label
+        serialized = self.serialize(self.make_cs_content({"anonymous": anonymous}))
+        assert serialized["author_label"] == expected_label
+
     def test_abuse_flagged(self):
         serialized = self.serialize(
             self.make_cs_content({"abuse_flaggers": [str(self.user.id)]})