old_contents: from openerp import models, api, fields
  
  
  class account_fiscal_position(models.Model):
  
      _inherit = 'account.fiscal.position'
  
      @api.v8     # noqa
      def map_tax(self, taxes):
          result = super(account_fiscal_position, self).map_tax(taxes)
          taxes_without_src_ids = [
              x.tax_dest_id.id for x in self.tax_ids if not x.tax_src_id]
          result += result.browse(taxes_without_src_ids)
          return result
  
  
  class account_fiscal_position_tax(models.Model):
      _inherit = 'account.fiscal.position.tax'
  
      tax_src_id = fields.Many2one(required=False)
  
new_contents: from openerp import models, api, fields
  
  
  class account_fiscal_position(models.Model):
  
      _inherit = 'account.fiscal.position'
  
      @api.v7
      def map_tax(self, cr, uid, fposition_id, taxes, context=None):
          result = super(account_fiscal_position, self).map_tax(
              cr, uid, fposition_id, taxes, context=context)
          taxes_without_src_ids = [
              x.tax_dest_id.id for x in fposition_id.tax_ids if not x.tax_src_id]
          result = set(result) | set(taxes_without_src_ids)
          return list(result)
  
      @api.v8     # noqa
      def map_tax(self, taxes):
          result = super(account_fiscal_position, self).map_tax(taxes)
          taxes_without_src_ids = [
              x.tax_dest_id.id for x in self.tax_ids if not x.tax_src_id]
          result += result.browse(taxes_without_src_ids)
          return result
  
  
  class account_fiscal_position_tax(models.Model):
      _inherit = 'account.fiscal.position.tax'
  
      tax_src_id = fields.Many2one(required=False)
  
subject: FIX fiscal position no source tax on v7 api