[FIX] account: Negative fixed taxes on 100% discount

Issue

	- Install 'Accounting' module
	- Create a new 'Tax' X with a fixed price (e.g.: O.O57 $)
	- Create a new 'Customer Invoice'
	- Add a product P and set unit price to 0 $
	- Set tax X to product P

	Total tax amount : - 0.06 $ .

Solution

	The sign must be forced to a negative sign in case the balance is on credit
	to avoid negatif taxes amount.

enterprise PR : https://github.com/odoo/enterprise/pull/15035

opw-2378978

closes odoo/odoo#62758

X-original-commit: 684855529e8aaafa0cb90f958d19c563d6e2a897
Related: odoo/enterprise#15105
Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>
Signed-off-by: bon-odoo <nboulif@users.noreply.github.com>

addons/account/models/account_move.py

@@ -529,6 +529,17 @@ class AccountMove(models.Model):
             'tax_tag_ids': [(6, 0, tax_vals['tag_ids'])],
         }
 
+    def _get_tax_force_sign(self):
+        """ The sign must be forced to a negative sign in case the balance is on credit
+            to avoid negatif taxes amount.
+            Example - Customer Invoice :
+            Fixed Tax  |  unit price  |   discount   |  amount_tax  | amount_total |
+            -------------------------------------------------------------------------
+                0.67   |      115      |     100%     |    - 0.67    |      0
+            -------------------------------------------------------------------------"""
+        self.ensure_one()
+        return -1 if self.move_type in ('out_invoice', 'in_refund', 'out_receipt') else 1
+
     def _recompute_tax_lines(self, recompute_tax_base_amount=False):
         ''' Compute the dynamic tax lines of the journal entry.
 
@@ -570,7 +581,7 @@ class AccountMove(models.Model):
                 is_refund = (tax_type == 'sale' and base_line.debit) or (tax_type == 'purchase' and base_line.credit)
                 price_unit_wo_discount = base_line.balance
 
-            balance_taxes_res = base_line.tax_ids._origin.compute_all(
+            balance_taxes_res = base_line.tax_ids._origin.with_context(force_sign=move._get_tax_force_sign()).compute_all(
                 price_unit_wo_discount,
                 currency=base_line.currency_id,
                 quantity=quantity,
@@ -3213,7 +3224,8 @@ class AccountMoveLine(models.Model):
 
         # Compute 'price_total'.
         if taxes:
-            taxes_res = taxes._origin.compute_all(line_discount_price_unit,
+            force_sign = -1 if move_type in ('out_invoice', 'in_refund', 'out_receipt') else 1
+            taxes_res = taxes._origin.with_context(force_sign=force_sign).compute_all(line_discount_price_unit,
                 quantity=quantity, currency=currency, product=product, partner=partner, is_refund=move_type in ('out_refund', 'in_refund'))
             res['price_subtotal'] = taxes_res['total_excluded']
             res['price_total'] = taxes_res['total_included']
@@ -3325,7 +3337,7 @@ class AccountMoveLine(models.Model):
             # 220           | 10% incl, 5%  |                   | 200               | 230
             # 20            |               | 10% incl          | 20                | 20
             # 10            |               | 5%                | 10                | 10
-            taxes_res = taxes._origin.compute_all(amount_currency, currency=currency, handle_price_include=False)
+            taxes_res = taxes._origin.with_context(force_sign=self.move_id._get_tax_force_sign()).compute_all(amount_currency, currency=currency, handle_price_include=False)
             for tax_res in taxes_res['taxes']:
                 tax = self.env['account.tax'].browse(tax_res['id'])
                 if tax.price_include:

addons/account/models/account_tax.py

@@ -439,9 +439,12 @@ class AccountTax(models.Model):
         # For the computation of move lines, we could have a negative base value.
         # In this case, compute all with positive values and negate them at the end.
         sign = 1
+        if currency.is_zero(base):
+            sign = self._context.get('force_sign', 1)
+        elif base < 0:
+            sign = -1
         if base < 0:
             base = -base
-            sign = -1
 
         # Store the totals to reach when using price_include taxes (only the last price included in row)
         total_included_checkpoints = {}

addons/account_edi_facturx/models/account_edi_format.py

@@ -68,7 +68,7 @@ class AccountEdiFormat(models.Model):
         # Invoice lines.
         for i, line in enumerate(invoice.invoice_line_ids.filtered(lambda l: not l.display_type)):
             price_unit_with_discount = line.price_unit * (1 - (line.discount / 100.0))
-            taxes_res = line.tax_ids.compute_all(
+            taxes_res = line.tax_ids.with_context(force_sign=line.move_id._get_tax_force_sign()).compute_all(
                 price_unit_with_discount,
                 currency=line.currency_id,
                 quantity=line.quantity,

addons/l10n_latam_invoice_document/models/account_move_line.py

@@ -30,7 +30,7 @@ class AccountMoveLine(models.Model):
                 invoice.l10n_latam_document_type_id and invoice.l10n_latam_document_type_id._filter_taxes_included(
                     line.tax_ids)
             if not included_taxes:
-                price_unit = line.tax_ids.with_context(round=False).compute_all(
+                price_unit = line.tax_ids.with_context(round=False, force_sign=invoice._get_tax_force_sign()).compute_all(
                     line.price_unit, invoice.currency_id, 1.0, line.product_id, invoice.partner_id)
                 l10n_latam_price_unit = price_unit['total_excluded']
                 l10n_latam_price_subtotal = line.price_subtotal
@@ -38,11 +38,11 @@ class AccountMoveLine(models.Model):
                 l10n_latam_price_net = l10n_latam_price_unit * (1 - (line.discount or 0.0) / 100.0)
             else:
                 not_included_taxes = line.tax_ids - included_taxes
-                l10n_latam_price_unit = included_taxes.compute_all(
+                l10n_latam_price_unit = included_taxes.with_context(force_sign=invoice._get_tax_force_sign()).compute_all(
                     line.price_unit, invoice.currency_id, 1.0, line.product_id, invoice.partner_id)['total_included']
                 l10n_latam_price_net = l10n_latam_price_unit * (1 - (line.discount or 0.0) / 100.0)
                 price = line.price_unit * (1 - (line.discount or 0.0) / 100.0)
-                l10n_latam_price_subtotal = included_taxes.compute_all(
+                l10n_latam_price_subtotal = included_taxes.with_context(force_sign=invoice._get_tax_force_sign()).compute_all(
                     price, invoice.currency_id, line.quantity, line.product_id,
                     invoice.partner_id)['total_included']
 

addons/purchase_stock/models/account_invoice.py

@@ -123,7 +123,7 @@ class AccountMove(models.Model):
                     # Since compute_all still rounds the total, we use an ugly workaround:
                     # multiply then divide the price unit.
                     price_unit *= line.quantity
-                    price_unit = line.tax_ids.with_context(round=False).compute_all(
+                    price_unit = line.tax_ids.with_context(round=False, force_sign=move._get_tax_force_sign()).compute_all(
                         price_unit, currency=move.currency_id, quantity=1.0, is_refund=move.move_type == 'in_refund')['total_excluded']
                     price_unit /= line.quantity