Propagating errors from Blueprint Error Handlers to App's Error Handlers

[Vimal-Kumar-V]

I have a use case where I need to perform cleanup and rollback operations when a specific exception class is raised in any of the view functions registered to a particular Flask blueprint. After completing the cleanup, I want to propagate this exception to Flask's global error handler, which performs additional cleanup and formats the error response.

I am considering explicitly calling app.handle_user_exception(exception), but this requires importing the entire app context into the utility layer, which seems unnecessary.

1. Am I doing something wrong conceptually?
2. Is there a better way to achieve this without manually invoking handle_user_exception?

Would appreciate any insights or best practices for handling such scenarios in Flask.

[davidism]

Re-raise the error from the blueprint's error handler.

[Vimal-Kumar-V]

Hi @davidism,

Thanks for taking the time to respond—I really appreciate it!

I had already tried your solution beforehand, but it doesn’t quite solve my use case. When an error is reraised from a Flask Blueprint, the handle_exception method steps in and wraps it as an InternalServerError. As a result, even if my Blueprint's error handler catches a 403 or 404 and raises it, Flask may override it and convert it into a 500 error, triggering a completely different error handler.

However, I’d like the error to propagate and be handled according to its actual status code.

Sorry if this sounds a bit basic—I’m just getting started with Flask and still figuring out how everything fits together.