class SaleOrderInherit(models.Model):
    _inherit = 'sale.order'


    @api.onchange('order_line')
    def _onchange_check_lines(self):
        for rec in self:
            for line in rec.order_line:
                if line.product_id.qty_available == 0:
                    raise ValidationError("Item is not in Stock")

class SaleOrderInherit(models.Model):
    _inherit = 'sale.order'

 

    @api.model
    def create(self, vals_list):
        res = super(SaleOrderInherit, self).create(vals_list)
        order_id = res.order_line
        for rec in order_id:
            if rec.product_id.qty_available == 0:
                raise ValidationError("Item is not in Stock")
        return res