Dynamic domain for M2O field without on change trigger in Odoo

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I had a class in some module

class Projects(models.Model):
    _name = 'crm.projects'
    product_lines = fields.Many2many(comodel_name="p.lines")

And a class in another module

class CustomLead(models.Model):
    _inherit = 'crm.lead'
     project = fields.Many2one(comodel_name="crm.projects")
     product_lines = fields.Many2one(comodel_name="p.lines")

Note that crm.projects.product_lines is M2M while crm.lead.product_lines is M2O.

The crm.projects’s form has a button that opens wizard of the crm.lead class and filters data in the crm.lead.product_lines to be only the tags selected in the crm.projects.product_lines

Let’s explain that more…

You know that M2M field takes tags widget in the XML view while M2O takes the drop-down list view , So imagine p.lines has A, B, C, D records. and in crm.projects form I have selected only tags A, B in the product_lines so after I click the button that opens crm.lead wizard it will let me only select A or B in the crm.lead.product_lines . That’s done easily using on change trigger dynamic domain on that field.

domain = {'product_lines': [('id', 'in', self.project.product_lines.ids)]}

The problem is that if I go to the screen of records created from that wizard and edit the field project_lines, the domain filter won’t work and you can see C, D also not only A,B.

Solution to this problem using the following modification in the class CustomLead

That’s it! now it works as expected.