Thank you, I tried this code but I got this error when I enter a transfer: Something went wrong !
×
stock.move.line(142974,).product_alternative

You can send a log return here to we analyse easily. Or send the user error return completely

That's the error: 'stock.move.line(142974,).product_alternative', None and the one I sent before

Try remove the depends decorator

I done a little correction in api.depends decorator. I expect this is the solution. Try this:

@api.depends('alternative_delivery_item')

@api.onchange('product_id')
def _computed_product_id(self):
# self.ensure_one()
for rec in self:
if rec.alternative_delivery_item == True:
rec.product_alternative = rec.product_id

That is the new update and its working fine. But I need the onchange function to execute only once. Is there any condition that can help me limit this?

You will can create a field where be created a execution condition to method. For example:

product_alternative_processed = fields.Boolean(string='Processed Product Alternative', deafult=False)

Every time you run this method check if the field has been calculated. Otherwise, you will edit the field.