[FIX] account, point_of_sale: correct tax_audit computation for pos returns

https://github.com/odoo/enterprise/pull/12091 changed the way the tax report computes its totals wit account moves resulting for return operations in pos. This commit does the same on tax_audit field, so that it stays consistent with the report.

closes odoo/odoo#55664

X-original-commit: 67b3d70c8425dee17731e7b94bcb4797d4b06a97
Related: odoo/enterprise#12320
Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>

addons/account/models/account_move.py

@@ -3473,7 +3473,7 @@ class AccountMoveLine(models.Model):
                     # Cash basis entries are always treated as misc operations, applying the tag sign directly to the balance
                     type_multiplicator = 1
                 else:
-                    type_multiplicator = (record.journal_id.type == 'sale' and -1 or 1) * (record.move_id.move_type in ('in_refund', 'out_refund') and -1 or 1)
+                    type_multiplicator = (record.journal_id.type == 'sale' and -1 or 1) * (self._get_refund_tax_audit_condition(record) and -1 or 1)
 
                 tag_amount = type_multiplicator * (tag.tax_negate and -1 or 1) * record.balance
 
@@ -3489,6 +3489,13 @@ class AccountMoveLine(models.Model):
 
             record.tax_audit = audit_str
 
+    def _get_refund_tax_audit_condition(self, aml):
+        """ Returns the condition to be used for the provided move line to tell
+        whether or not it comes from a refund operation.
+        This is overridden by pos in order to treat returns properly.
+        """
+        return aml.move_id.move_type in ('in_refund', 'out_refund') and -1 or 1
+
     # -------------------------------------------------------------------------
     # CONSTRAINT METHODS
     # -------------------------------------------------------------------------

addons/point_of_sale/models/account_move.py

@@ -35,3 +35,15 @@ class AccountMoveLine(models.Model):
         if order:
             price_unit = order._get_pos_anglo_saxon_price_unit(self.product_id, self.move_id.partner_id.id, self.quantity)
         return price_unit
+
+    def _get_refund_tax_audit_condition(self, aml):
+        # Overridden so that the returns can be detected as credit notes by the tax audit computation
+        rslt = super()._get_refund_tax_audit_condition(aml)
+
+        if aml.move_id.is_invoice():
+            # We don't need to check the pos orders for this move line if an invoice
+            # is linked to it ; we know that the invoice type tells us whether it's a refund
+            return rslt
+
+        pos_orders_count = self.env['pos.order'].search_count([('account_move', '=', aml.move_id.id)])
+        return rslt or (pos_orders_count and aml.debit > 0)