A pair of customers have this same problem: they neet to quickly see the stock movement linked to the invoice.

Since there is no direct link between stock move and invoice, I want to lean myself in the fact they are using the pos. This way I found that picking_id is in stock.move, and in pos.order. Then pos.order has invoice_id as a field.

So I wrote something like this:

class stock_move_invoice_number(models.Model):
    _name = "stock.move"
    _inherit = "stock.move"

    invoice_number = fields.Char(
        string='Invoice Number', compute='_get_inv_number', help='Invoice Number'
    )
       
    @api.depends('picking_id')
    def _get_inv_number(self):
        for x in self:
            print x.picking_id
            po = x.env['pos.order'].search([('picking_id', '=', x.picking_id)], limit=1)
            x.invoice_number = po.invoice_id.afip_document_number 

But I get an error in the domain:

AssertionError: Invalid value stock.picking(1150,) in domain term ('picking_id', '=', stock.picking(1150,))

If I hardcode the value 1150 as int in the domain, I am getting what I need, so the idea works, but I can't catch the picking_id number away from the x.picking_id object.

Is there a better approach?