Hi,

Please refer to the code below:

from odoo import models, fields, api
from odoo.exceptions import ValidationError

class ResPartner(models.Model):
    """
        Inherits the res.partner model to add a 'lookup_status' field.

        This field is an internal indicator managed by backend processes.
        It is set to readonly to prevent manual edits through the UI.

        Constraints:
            - The field 'lookup_status' must not be zero after any update.
              Attempting to set it to 0 will raise a ValidationError.
        """

    _inherit = 'res.partner'

    lookup_status = fields.Integer(string="Lookup Status", tracking=True,
                                   readonly=True, default=0)

    @api.constrains('lookup_status')
    def _check_lookup_status(self):
        """
            Constraint to ensure that 'lookup_status' is never set to 0.

            This method is automatically triggered whenever the 'lookup_status'
            field is modified. It raises a ValidationError if the value is set to 0,
            enforcing a business rule that prohibits this status value.

            Raises:
                ValidationError: If 'lookup_status' is equal to 0.
            """
        for rec in self:
            if rec.lookup_status == 0:
                raise ValidationError(_('EP Lookup status cannot be 0'))

@api.constrains checks actual field values on the record after creation/update. It works regardless of whether the field was part of the original vals or changed indirectly.write() logic triggers for explicit values passed in the vals dictionary.

Hope it helps.

Yes these are the same, the status is changed in a .py when i fetch some data. The status is displayed correct, according to the current value, but not in the vals. There are only in vals when the user touch the field. So all writes will not recognise when the change by a program. The fields needs deforced to update. Think need to write a work around, with a cache / buffer to updater the vals.

her is a slimline example of the problem, also with the workaround to get it working with an bi=uffer to store the value.

import logging


from odoo import api, fields, models
from odoo.addons.bag_ep_api.utils.buffer_manager import BufferManager
from odoo.exceptions import ValidationError


_logger = logging.getLogger(__name__)


#  Odoo version 18

class ResPartner(models.Model):
    _inherit = 'res.partner'
    
    ep_lookup_status = fields.Integer(
       string = "EP Lookup status",
       tracking = True,
       readonly = True,
       default = 0
       )
    
    
    @api.model_create_multi
    def create(self, vals_list):
       partners = super().create(vals_list)
       
       return partners
    
    
    def write(self, vals):
       
       # if buffer is not active, this will do nothing, also no message the api.constrains will also not work
       # when activate in the _onchange it wil preform exact as expected, workaround
       buffer = BufferManager.get(self.env.user.id)
       if buffer:
          for key in buffer:
             if key not in vals:
                vals[key] = buffer[key]
       
       result = super().write(vals)
       for record in self:
          
          if record.ep_lookup_status == 0:
             raise ValidationError('Lookup status cannot be 0')
       
       return result
    
    
    @api.constrains('ep_lookup_status')
    def _check_ep_lookup_status(self):
       for rec in self:
          if rec.ep_lookup_status == 0:
             raise ValidationError('Lookup status cannot be 0')
    
    
    @api.onchange('zip')
    def _onchange_zip(self):
       
       # some other code with channing the ep_lookup_status
       # for demo
       
       if self.zip == '2035 VS':
          self.ep_lookup_status = 1;
       else:
          self.ep_lookup_status = 0;
       
       BufferManager.set(self.env.user.id,'ep_lookup_status', self.ep_lookup_status)
       
       return self._handle_onchange_result(
          ep_lookup_status = self.ep_lookup_status,
          )
    
    
    @staticmethod
    def _handle_onchange_result(warnings = None, model_name = None, data_model = None, ep_lookup_status = None):
       #     #
       result = {}
       warnings = {}
       
       # some other to infor the user(s)
       
       # Show a warning message if needed
       if warnings:
          result['warning'] = {
             'title': " -- Warning -- ",
             'message': "\n".join(warnings),
             }
       
       return result or None

Hello RacketRebel,

Try below code : 

def write(self, vals):

    res = super().write(vals)

    for rec in self:

        if rec.lookup_status == 0:

            raise ValidationError(_('EP Lookup status cannot be 0'))

        else:

            rec.update({'lookup_status':rec.lookup_status})

    return res

thanks.

Hii,

Why Your Check Fails

Your logic:

It only works if lookup_status is in vals, but:

• If the field was updated via code, and
• You're calling record.write({}) or record.write({'other_field': val})

Then lookup_status won’t be in vals, so your check silently skips.

Here is updated code 
Check current field value directly on self

If you want to ensure the value isn’t 0 when any write() happens:

def write(self, vals):

    res = super().write(vals)

    for rec in self:

        if rec.lookup_status == 0:

            raise ValidationError(_('EP Lookup status cannot be 0'))

    return res

try this 

i hope it is use full