dosubot[bot] commented on issue #41001:
URL: https://github.com/apache/superset/issues/41001#issuecomment-4710447795
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@sadpandajoe I've confirmed this bug is valid. Here's the summary:
**Root Cause Confirmed**
In `superset/mcp_service/dashboard/schemas.py`, the `dashboard_serializer()`
function uses `RoleInfo.model_validate(role, from_attributes=True)` to
serialize dashboard roles . Since `RoleInfo.permissions` is typed as `List[str]
| None` , Pydantic attempts to coerce `PermissionView` ORM objects into
strings, which triggers a lazy load of `PermissionView.permission` — and
because the MCP ASGI sub-app has already detached the SQLAlchemy session, this
raises `DetachedInstanceError`.
**The fix already exists in the same file** — `serialize_role_object()`
correctly extracts permission names as strings:
```python
permissions=[perm.name for perm in getattr(role, "permissions", [])]
```
**Recommended Fix**
Replace the `model_validate` calls in `dashboard_serializer()` (and any
other serialization paths like `build_dashboard_info()`) with the existing
helper:
```python
# Before (broken):
roles=[
RoleInfo.model_validate(role, from_attributes=True)
for role in dashboard.roles
]
# After (fixed):
roles=[
serialize_role_object(role)
for role in dashboard.roles
]
```
This is consistent with how other ORM objects are serialized in the MCP
service (e.g., `serialize_user_object`, `serialize_tag_object`,
`serialize_chart_object` all follow the helper pattern). The
`model_validate(..., from_attributes=True)` approach is simply incompatible
with lazy-loaded nested relationships in the detached-session context of the
MCP ASGI sub-app.
A related issue was also reported in
[#40423](https://github.com/apache/superset/issues/40423) with the same
`DetachedInstanceError` on `PermissionView` in `list_dashboards`.
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