frappe-impl-controllers

To override ERPNext doctype controllers correctly, use super() calls and alternative event-driven handlers, including v16+ extend_doctype_class, to ensure production-safe extension patterns without breaking core workflows.

Use db_set or set_value to persist changes safely in Frappe lifecycle hooks during post-save events like on_update, because direct mutations to self are not automatically saved after the document is inserted.

Structure Frappe submit and cancel workflows by selecting the correct controller hooks, specifically before_submit, on_submit, before_cancel, and on_cancel, to manage state changes and side effects cleanly.

Pass state between Frappe validation and on_update hooks by using flags, which provide flags-based inter-hook communication to securely share data across different controller events without relying on global variables.

Yes, this approach works for migrating logic from hooks.py and server scripts to Frappe doctype controllers by applying proper hook semantics and production-grade patterns to ensure correct timing and safe persistence.

Your Frappe controller changes are not saving during on_update because standard validation and mutation rules require using db_set or set_value to persist post-save updates safely, as modifications to self are lost after insertion.