[FIX] point_of_sale : prevent to unlink pos.order.line related to 'paid' / 'invoiced' order.

closes odoo/odoo#126558

X-original-commit: 52631ac88c1ec8f6f5fd6542d6b38a200f83372c
Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>

addons/point_of_sale/models/pos_order.py

@@ -1392,6 +1392,11 @@ class PosOrderLine(models.Model):
                     del pl[2]['server_id']
         return super().write(values)
 
+    @api.ondelete(at_uninstall=False)
+    def _unlink_except_order_state(self):
+        if self.filtered(lambda x: x.order_id.state not in ["draft", "cancel"]):
+            raise UserError(_("You can only unlink PoS order lines that are related to orders in new or cancelled state."))
+
     @api.onchange('price_unit', 'tax_ids', 'qty', 'discount', 'product_id')
     def _onchange_amount_line_all(self):
         for line in self: