Hi,

It will be difficult to control with xml file. But we have different options to avoid duplicate products. Either you can give _sql_constarints for this field or you can override the create method and check whether any records existing with same internal reference.

Having products with the same internal code or the same product name is a nonsense.

This kind of practice should be avoided (banned).

This is also true for the  barcode identification field.

All, must be unique.

Just use: https://www.odoo.com/apps/7.0/product_unique/  and https://www.odoo.com/apps/7.0/product_name_unique_per_company/ to avoid this type of errors.

XML view definitions are only 'aware' of the current record so I don't see how this is possible with XML.

Dear,

To check exist the same Product in the line level.

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


class PurchaseOrder(models.Model):
    _inherit = "purchase.order"

    @api.multi
    @api.constrains('order_line')
    def _check_exist_product_in_line(self):
      for purchase in self:
          exist_product_list = []
          for line in purchase.order_line:
             if line.product_id.id in exist_product_list:
                raise ValidationError(_('Product should be one per line.'))
             exist_product_list.append(line.product_id.id)

Hope this code help you

Best Thanks,

Ankit H Gandhi.