[FIX] account,point_of_sale: Allow mixing 'affect base' price-included/price-excluded taxes

Before this commit, such configuration wasn't allowed.
However, in some countries, this is mandatory, when dealing with eco-tax for example:

Suppose t1, t2 being taxes where:
- t1 is include_base_amount, price_excluded, fixed tax of 10 (eco-tax)
- t2 is include_base_amount, price_included, percent of 21%

The computation on 1210 should be:
price_excluded: 1210 / 1.21 = 1000
price_included: (1000 + 10) * 1.21 = 1222.1

closes odoo/odoo#69184

Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>

3 files changed, 50 insertions, 36 deletions

diff --git a/addons/account/models/account_tax.py b/addons/account/models/account_tax.py
index 109123d2ce8..59790f1b435 100644
--- a/addons/account/models/account_tax.py
+++ b/addons/account/models/account_tax.py
@@ -370,22 +370,10 @@ class AccountTax(models.Model):
         # 1) Flatten the taxes.
         taxes, groups_map = self.flatten_taxes_hierarchy(create_map=True)
 
-        # 2) Avoid mixing taxes having price_include=False && include_base_amount=True
-        # with taxes having price_include=True. This use case is not supported as the
-        # computation of the total_excluded would be impossible.
-        base_excluded_flag = False  # price_include=False && include_base_amount=True
-        included_flag = False  # price_include=True
-        for tax in taxes:
-            if tax.price_include:
-                included_flag = True
-            elif tax.include_base_amount:
-                base_excluded_flag = True
-            if base_excluded_flag and included_flag:
-                raise UserError(_('Unable to mix any taxes being price included with taxes affecting the base amount but not included in price.'))
-
-        # 3) Deal with the rounding methods
+        # 2) Deal with the rounding methods
         if not currency:
             currency = company.currency_id
+
         # By default, for each tax, tax amount will first be computed
         # and rounded at the 'Account' decimal precision for each
         # PO/SO/invoice line and then these rounded amounts will be
@@ -408,7 +396,7 @@ class AccountTax(models.Model):
         if not round_tax:
             prec *= 1e-5
 
-        # 4) Iterate the taxes in the reversed sequence order to retrieve the initial base of the computation.
+        # 3) Iterate the taxes in the reversed sequence order to retrieve the initial base of the computation.
         #     tax  |  base  |  amount  |
         # /\ ----------------------------
         # || tax_1 |  XXXX  |          | <- we are looking for that, it's the total_excluded
@@ -515,10 +503,15 @@ class AccountTax(models.Model):
 
         total_excluded = currency.round(recompute_base(base, incl_fixed_amount, incl_percent_amount, incl_division_amount))
 
-        # 5) Iterate the taxes in the sequence order to compute missing tax amounts.
+        # 4) Iterate the taxes in the sequence order to compute missing tax amounts.
         # Start the computation of accumulated amounts at the total_excluded value.
         base = total_included = total_void = total_excluded
 
+        # Flag indicating the checkpoint used in price_include to avoid rounding issue must be skipped since the base
+        # amount has changed because we are currently mixing price-included and price-excluded include_base_amount
+        # taxes.
+        skip_checkpoint = False
+
         taxes_vals = []
         i = 0
         cumulated_tax_included_amount = 0
@@ -529,7 +522,7 @@ class AccountTax(models.Model):
             price_include = self._context.get('force_price_include', tax.price_include)
 
             #compute the tax_amount
-            if price_include and total_included_checkpoints.get(i):
+            if not skip_checkpoint and price_include and total_included_checkpoints.get(i):
                 # We know the total to reach for that tax, so we make a substraction to avoid any rounding issues
                 tax_amount = total_included_checkpoints[i] - (base + cumulated_tax_included_amount)
                 cumulated_tax_included_amount = 0
@@ -594,6 +587,8 @@ class AccountTax(models.Model):
             # Affect subsequent taxes
             if tax.include_base_amount:
                 base += factorized_tax_amount
+                if not price_include:
+                    skip_checkpoint = True
 
             total_included += factorized_tax_amount
             i += 1
diff --git a/addons/account/tests/test_tax.py b/addons/account/tests/test_tax.py
index 532ca7eb0c3..068031ceac0 100644
--- a/addons/account/tests/test_tax.py
+++ b/addons/account/tests/test_tax.py
@@ -1045,3 +1045,31 @@ class TestTax(TestTaxCommon):
             ],
             res3
         )
+
+    def test_mixing_price_included_excluded_with_affect_base(self):
+        tax_10_fix = self.env['account.tax'].create({
+            'name': "tax_10_fix",
+            'amount_type': 'fixed',
+            'amount': 10.0,
+            'include_base_amount': True,
+        })
+        tax_21 = self.env['account.tax'].create({
+            'name': "tax_21",
+            'amount_type': 'percent',
+            'amount': 21.0,
+            'price_include': True,
+            'include_base_amount': True,
+        })
+
+        self._check_compute_all_results(
+            1222.1,     # 'total_included'
+            1000.0,     # 'total_excluded'
+            [
+                # base , amount
+                # ---------------
+                (1000.0, 10.0),
+                (1010.0, 212.1),
+                # ---------------
+            ],
+            (tax_10_fix + tax_21).compute_all(1210),
+        )
diff --git a/addons/point_of_sale/static/src/js/models.js b/addons/point_of_sale/static/src/js/models.js
index 4423904b722..3c9aa1ed5c8 100644
--- a/addons/point_of_sale/static/src/js/models.js
+++ b/addons/point_of_sale/static/src/js/models.js
@@ -2153,21 +2153,7 @@ exports.Orderline = Backbone.Model.extend({
 
         taxes = collect_taxes(taxes);
 
-        // 2) Avoid dealing with taxes mixing price_include=False && include_base_amount=True
-        // with price_include=True
-
-        var base_excluded_flag = false; // price_include=False && include_base_amount=True
-        var included_flag = false;      // price_include=True
-        _(taxes).each(function(tax){
-            if(tax.price_include)
-                included_flag = true;
-            else if(tax.include_base_amount)
-                base_excluded_flag = true;
-            if(base_excluded_flag && included_flag)
-                throw new Error('Unable to mix any taxes being price included with taxes affecting the base amount but not included in price.');
-        });
-
-        // 3) Deal with the rounding methods
+        // 2) Deal with the rounding methods
 
         var round_tax = this.pos.company.tax_calculation_rounding_method != 'round_globally';
 
@@ -2175,7 +2161,7 @@ exports.Orderline = Backbone.Model.extend({
         if(!round_tax)
             currency_rounding = currency_rounding * 0.00001;
 
-        // 4) Iterate the taxes in the reversed sequence order to retrieve the initial base of the computation.
+        // 3) Iterate the taxes in the reversed sequence order to retrieve the initial base of the computation.
         var recompute_base = function(base_amount, fixed_amount, percent_amount, division_amount){
              return (base_amount - fixed_amount) / (1.0 + percent_amount / 100.0) * (100 - division_amount) / 100;
         }
@@ -2230,15 +2216,17 @@ exports.Orderline = Backbone.Model.extend({
         var total_excluded = round_pr(recompute_base(base, incl_fixed_amount, incl_percent_amount, incl_division_amount), initial_currency_rounding);
         var total_included = total_excluded;
 
-        // 5) Iterate the taxes in the sequence order to fill missing base/amount values.
+        // 4) Iterate the taxes in the sequence order to fill missing base/amount values.
 
         base = total_excluded;
 
+        var skip_checkpoint = false;
+
         var taxes_vals = [];
         i = 0;
         var cumulated_tax_included_amount = 0;
         _(taxes.reverse()).each(function(tax){
-            if(tax.price_include && total_included_checkpoints[i] !== undefined){
+            if(!skip_checkpoint && tax.price_include && total_included_checkpoints[i] !== undefined){
                 var tax_amount = total_included_checkpoints[i] - (base + cumulated_tax_included_amount);
                 cumulated_tax_included_amount = 0;
             }else
@@ -2256,8 +2244,11 @@ exports.Orderline = Backbone.Model.extend({
                 'base': sign * round_pr(base, currency_rounding),
             });
 
-            if(tax.include_base_amount)
+            if(tax.include_base_amount){
                 base += tax_amount;
+                if(!tax.price_include)
+                    skip_checkpoint = true;
+            }
 
             total_included += tax_amount;
             i += 1;