frappe-impl-controllers

To override standard ERPNext controllers safely, extend the base class and apply flags-based coordination to preserve saved field changes. This approach maintains lifecycle-safe validation and prevents common anti-patterns that break submit, cancel, or delete workflows in production ERPNext apps.

Common Frappe controller anti-patterns include placing heavy or external work inside validation paths, ignoring flags for coordination, and mishandling child table or submittable document lifecycles. Avoiding these mistakes requires keeping validation lightweight and preserving saved field changes during on_update.

Testing Frappe document controllers involves writing controller tests that exercise insert, save, submit, cancel, and delete workflows for custom app DocTypes. Practical examples include validating saved calculations, custom naming, and linked-document updates to ensure lifecycle-safe behavior in production scenarios.

Handling child table and submittable document behavior in Frappe requires extending the appropriate controller class and applying lifecycle hooks like before_submit or on_cancel. Using flags-based coordination ensures parent-child data integrity and prevents validation errors during save and submit workflows.