I have developer mode activated. For example I see that when I press "Validate" it calls invoice_validate(). But also it calls action_date_assign() , action_move_create()

when you validate an entry corresponding journal entries are created it is done using another method.

I understand. But how can I see ALL methods called when I click "Validate" button?

i'm not sure if there is a easy way to know all methods. what you should do is find the method which is called when you click 'validate' button from there you should find other methods calling inside that and so on..

The action for the button is only invoice_validate() . Inside that, not calls anything, but before calling invoice_validate() Odoo calls action_date_assign() ... and how can I determine that!?