fix(dashboards): Prevent IndexError for deleted dashboard creators

src/sentry/api/serializers/models/dashboard.py

@@ -682,9 +682,20 @@ def get_attrs(self, item_list, user, **kwargs):
             user=user,
         )
 
+        creator_ids = [d.created_by_id for d in item_list if d.created_by_id is not None]
+        serialized_creators = (
+            user_service.serialize_many(filter={"user_ids": creator_ids}) if creator_ids else []
+        )
+        serialized_users = {u["id"]: u for u in serialized_creators}
+
         for dashboard in item_list:
             dashboard_widgets = [w for w in widgets if w and w["dashboardId"] == str(dashboard.id)]
-            result[dashboard] = {"widgets": dashboard_widgets}
+            created_by = (
+                serialized_users.get(str(dashboard.created_by_id))
+                if dashboard.created_by_id is not None
+                else None
+            )
+            result[dashboard] = {"widgets": dashboard_widgets, "created_by": created_by}
 
         return result
 
@@ -695,11 +706,7 @@ def serialize(self, obj, attrs, user, **kwargs) -> DashboardDetailsResponse:
             "id": str(obj.id),
             "title": obj.title,
             "dateCreated": obj.date_added,
-            "createdBy": (
-                user_service.serialize_many(filter={"user_ids": [obj.created_by_id]})[0]
-                if obj.created_by_id
-                else None
-            ),
+            "createdBy": attrs.get("created_by"),
             "widgets": attrs["widgets"],
             "filters": tag_filters,
             "permissions": serialize(obj.permissions) if hasattr(obj, "permissions") else None,

tests/sentry/dashboards/endpoints/test_organization_dashboard_details.py

@@ -128,6 +128,19 @@ def test_get(self) -> None:
         assert len(widgets[1]["queries"]) == 1
         self.assert_serialized_widget_query(widgets[1]["queries"][0], self.widget_2_data_1)
 
+    def test_get_created_by_is_none_when_creator_deleted(self) -> None:
+        # Simulate a dashboard whose creator has been deleted: user_service returns
+        # an empty list for that user ID, which should yield createdBy=None instead
+        # of raising IndexError.
+        with mock.patch(
+            "sentry.api.serializers.models.dashboard.user_service.serialize_many",
+            return_value=[],
+        ):
+            response = self.do_request("get", self.url(self.dashboard.id))
+
+        assert response.status_code == 200, response.content
+        assert response.data["createdBy"] is None
+
     def test_dashboard_does_not_exist(self) -> None:
         response = self.do_request("get", self.url(1234567890))
         assert response.status_code == 404