File "/home/gowtham.a/workspace/odoo-18.0/odoo/models.py", line 6880, in __getitem__
    return self._fields[key].__get__(self)
  File "/home/gowtham.a/workspace/odoo-18.0/odoo/fields.py", line 1296, in __get__
    raise ValueError(f"Compute method failed to assign {missing_recs}.{self.name}")
ValueError: Compute method failed to assign account.move(2,).exchange_rate

class AccountMove(models.Model):   
    _inherit = "account.move"
    
    attn = fields.Many2one('res.partner',string="ATTN")
    customer_po_no = fields.Char(string="Customer PO No.")
    do_name = fields.Char(string="DO No.")
    exchange_rate = fields.Float(string="Rate",digits=(12,4),compute="_compute_currency_rate")


    def _compute_currency_rate(self):
        for mov in self:
            if mov.currency_id:

                if mov.company_id.country_id.code != 'SG':
                    currency_id_rates = self.env['res.currency.rate'].search([('currency_id','=',mov.currency_id.id),('company_id','=',mov.company_id.id)])
                    for currency_id_rate in currency_id_rates:
                        if currency_id_rate.name == mov.invoice_date:

                            mov.exchange_rate = currency_id_rate.rate
                            break
                        else:
                            if mov.invoice_date and currency_id_rate.name:
                                if currency_id_rate.name.month == mov.invoice_date.month and currency_id_rate.name.year == mov.invoice_date.year:
                                    mov.exchange_rate = currency_id_rate.rate
                                    break
                                else:
                                    mov.exchange_rate = currency_id_rate.rate
                            else:
                                mov.exchange_rate = currency_id_rate.rate
                                break
                else:
                    currency_id_rates = self.env['res.currency.rate'].search([('currency_id','=',mov.currency_id.id),('company_id','=',mov.company_id.id)])
                    for currency_id_rate in currency_id_rates:
                        if currency_id_rate.name == mov.invoice_date:
                            mov.exchange_rate = 1 / currency_id_rate.rate
                            break
                        else:
                            if mov.invoice_date and currency_id_rate.name:
                                if currency_id_rate.name.month == mov.invoice_date.month and currency_id_rate.name.year == mov.invoice_date.year:
                                    mov.exchange_rate = 1 / currency_id_rate.rate
                                    break
                                else:
                                    mov.exchange_rate = 1 / currency_id_rate.rate
                            else:
                                mov.exchange_rate = 1 / currency_id_rate.rate
                                break