Protect Cancel button with a confirmation pop-up

purchase_usability/purchase.py

@@ -16,6 +16,8 @@ class PurchaseOrder(models.Model):
     fiscal_position_id = fields.Many2one(track_visibility='onchange')
     incoterm_id = fields.Many2one(track_visibility='onchange')
     partner_ref = fields.Char(track_visibility='onchange')
+    # field 'partner_id': native value for track_visibility='always'
+    partner_id = fields.Many2one(track_visibility='onchange')
     # for report
     delivery_partner_id = fields.Many2one(
         'res.partner', compute='_compute_delivery_partner_id', readonly=True)

purchase_usability/purchase_view.xml

@@ -33,6 +33,9 @@
         <field name="fiscal_position_id" position="attributes">
             <attribute name="widget">selection</attribute>
         </field>
+        <button name="button_cancel" type="object" position="attributes">
+            <attribute name="confirm">Are you sure you want to cancel this purchase order?</attribute>
+        </button>
     </field>
 </record>