gistfile1.py

    def _amount_residual(self, cr, uid, ids, name, args, context=None):
        """Function of the field residua. It computes the residual amount (balance) for each invoice"""
        if context is None:
            context = {}
        ctx = context.copy()
        result = {}
        currency_obj = self.pool.get('res.currency')
        for invoice in self.browse(cr, uid, ids, context=context):
            nb_inv_in_partial_rec = max_invoice_id = 0
            result[invoice.id] = 0.0
            if invoice.move_id:
                for aml in invoice.move_id.line_id:
                    if aml.account_id.type in ('receivable','payable'):
                        if aml.currency_id and aml.currency_id.id == invoice.currency_id.id:
                            result[invoice.id] += aml.amount_residual_currency
                        else:
                            ctx['date'] = aml.date
                            result[invoice.id] += currency_obj.compute(cr, uid, aml.company_id.currency_id.id, invoice.currency_id.id, aml.amount_residual, context=ctx)

                        if aml.reconcile_partial_id.line_partial_ids:
                            #we check if the invoice is partially reconciled and if there are other invoices
                            #involved in this partial reconciliation (and we sum these invoices)
                            for line in aml.reconcile_partial_id.line_partial_ids:
                                if line.invoice:
                                    nb_inv_in_partial_rec += 1
                                    #store the max invoice id as for this invoice we will make a balance instead of a simple division
                                    max_invoice_id = max(max_invoice_id, line.invoice.id)
            if nb_inv_in_partial_rec:
                #if there are several invoices in a partial reconciliation, we split the residual by the number
                #of invoice to have a sum of residual amounts that matches the partner balance
                new_value = currency_obj.round(cr, uid, invoice.currency_id, result[invoice.id] / nb_inv_in_partial_rec)
                if invoice.id == max_invoice_id:
                    #if it's the last the invoice of the bunch of invoices partially reconciled together, we make a
                    #balance to avoid rounding errors
                    result[invoice.id] = result[invoice.id] - ((nb_inv_in_partial_rec - 1) * new_value)
                else:
                    result[invoice.id] = new_value

            #prevent the residual amount on the invoice to be less than 0
            result[invoice.id] = max(result[invoice.id], 0.0)
        return result