[FIX] website_sale: display correct price according in carousel

Steps to reproduce:
1) Create product P for $1000, with 15% Tax, publish to website.
1-bis) make sure the 15% tax is "included"
2) Settings -> search 'price' -> Tax Excluded.
3) Go to website /shop page, and edit to place the Products block, and search for

Issue:
The price displayed on the product in "86.96" (correct) but the price on the product in the carousel displays "100.00"

Cause:
The price for the carousel is not fetched the same way
https://github.com/odoo/odoo/blob/e829b345f0f5e5346be416b8354c29fa9acb74a7/addons/website_sale/data/product_snippet_template_data.xml#L388



And the method does not take into account this fourth scenario. That is:
- a tax with price_include set to True
- a show_line_subtotals_tax_selection config parameter set to "tax_excluded"

Note:
There is an issue with the case of a mapping from a tax included to a tax included:
```
param_main_product_tax_included = True
param_fpos = 'to_tax_included' # mapping from 15% to 10%
```
As if the product price is 100, the tax set on the product is 15%.
```
>>> self.env['account.tax']._fix_tax_included_price_company( price, product_taxes, taxes, self.env.company.id)
86.96
```
The price would be 100/1.15 = 86.96

And when calling `taxes.compute_all(price, product=self, partner=self.env['res.partner'])` it would return
```
included = 86.96 ; excluded = 79.05
```
The base is computed by taking the initial base such as
```
100/1.15/1.1 = 79.05
```
Instead of keeping the initial base and applying the new tax percentage to compute the total included
```
base = 100/1.15 = 86.96
total_included = 86.96 * 1.10 = 95.656
amount_tax = 8.696
```
After some discussion, it turns out this problem is a known issue. To make the mapping from 'tax_included' to 'tax_included' more sensible, we'd need to make some additional changes beyond what we're addressing in this fix.

opw-3370999

closes odoo/odoo#133501

Signed-off-by: Yolann Sabaux (yosa) <yosa@odoo.com>

addons/website_sale/models/product_product.py

@@ -100,7 +100,14 @@ class Product(models.Model):
         self.ensure_one()
         price = self._get_contextual_price()
         line_tax_type = self.env['ir.config_parameter'].sudo().get_param('account.show_line_subtotals_tax_selection')
-        company_taxes = self.taxes_id.filtered(lambda tax: tax.company_id == self.env.company)
-        if line_tax_type == "tax_included" and company_taxes:
-            price = company_taxes.compute_all(price, product=self, partner=self.env['res.partner'])['total_included']
+        fpos_id = self.env['website'].sudo()._get_current_fiscal_position_id(self.env.user.partner_id)
+        fiscal_position = self.env['account.fiscal.position'].sudo().browse(fpos_id)
+        product_taxes = self.sudo().taxes_id.filtered(lambda x: x.company_id == self.env.company)
+        if product_taxes:
+            taxes = fiscal_position.map_tax(product_taxes)
+            price = self.env['account.tax']._fix_tax_included_price_company(
+                price, product_taxes, taxes, self.env.company,
+            )
+            tax_display = "total_included" if line_tax_type == "tax_included" else "total_excluded"
+            price = taxes.compute_all(price, product=self, partner=self.env['res.partner'])[tax_display]
         return price

addons/website_sale/tests/test_website_sale_product.py

 # coding: utf-8
+import itertools
+
 from odoo.tests import tagged
 from odoo.addons.website.tools import MockRequest
 from odoo.addons.sale.tests.test_sale_product_attribute_value_config import TestSaleProductAttributeValueCommon
+from odoo.addons.website_sale.controllers.main import WebsiteSale
+
 
 @tagged('post_install', '-at_install')
 class WebsiteSaleProductTests(TestSaleProductAttributeValueCommon):
 
-    def setUp(self):
-        super().setUp()
-        self.website = self.env.ref('website.default_website')
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.WebsiteSaleController = WebsiteSale()
+        cls.website = cls.env.ref('website.default_website')
+
+        cls.tax_5 = cls.env['account.tax'].create({
+            'name': '5% Tax',
+            'amount_type': 'percent',
+            'amount': 5,
+            'price_include': False,
+            'include_base_amount': False,
+            'type_tax_use': 'sale',
+        })
+        cls.tax_10 = cls.env['account.tax'].create({
+            'name': '10% Tax',
+            'amount_type': 'percent',
+            'amount': 10,
+            'price_include': False,
+            'include_base_amount': False,
+            'type_tax_use': 'sale',
+        })
+        cls.tax_15 = cls.env['account.tax'].create({
+            'name': '15% Tax',
+            'amount_type': 'percent',
+            'amount': 15,
+            'price_include': False,
+            'include_base_amount': False,
+            'type_tax_use': 'sale',
+        })
+        cls.fiscal_country = cls.env['res.country'].create({
+            'name': "Super Fiscal Position",
+            'code': 'SFP',
+        })
+        cls.product = cls.env['product.product'].create({
+            'name': 'Super Product',
+            'list_price': 100.0,
+        })
 
     def test_website_sale_contextual_price(self):
         contextual_price = self.computer._get_contextual_price()
@@ -32,3 +71,73 @@ class WebsiteSaleProductTests(TestSaleProductAttributeValueCommon):
             2000.0 * currency_ratio * discount_rate, contextual_price,
             "With a website pricelist context, the contextual price should be the one defined for the website's pricelist."
         )
+
+    def test_get_contextual_price_tax_selection(self):
+        """
+        `_get_contextual_price_tax_selection` is used to display the price on the website (e.g. in the carousel).
+        We test that the contextual price is correctly computed. That is, it is coherent with the price displayed on the product when in the cart.
+        """
+        param_main_product_tax_included = [True, False]
+        param_show_line_subtotals_tax_selection = ['tax_included', 'tax_excluded']
+        param_extra_tax = [False, 'included', 'excluded']
+        param_fpos = [False, 'to_tax_excluded']
+        parameters = itertools.product(param_main_product_tax_included, param_show_line_subtotals_tax_selection, param_extra_tax, param_fpos)
+
+        for main_product_tax_included, show_line_subtotals_tax_selection, extra_tax, fpos in parameters:
+            with self.subTest(main_product_tax_included=main_product_tax_included, show_line_subtotals_tax_selection=show_line_subtotals_tax_selection, extra_tax=extra_tax, fpos=fpos):
+                # set "show_line_subtotals_tax_selection" parameter
+                config = self.env['res.config.settings'].create({})
+                config.show_line_subtotals_tax_selection = show_line_subtotals_tax_selection
+                config.execute()
+
+                # set "main_product_tax_included" parameter
+                if main_product_tax_included:
+                    self.tax_15.price_include = True
+                    self.tax_15.include_base_amount = True
+                self.product.taxes_id = self.tax_15
+                tax_ids = [self.tax_15.id]
+
+                # set "extra_tax" parameter
+                if extra_tax:
+                    if extra_tax == 'included':
+                        self.tax_5.price_include = True
+                        self.tax_5.include_base_amount = True
+                    tax_ids.append(self.tax_5.id)
+
+                # set "fpos" parameter
+                if fpos:
+                    if fpos == 'to_tax_included':
+                        self.tax_10.price_include = True
+                        self.tax_10.include_base_amount = True
+
+                    fiscal_position = self.env['account.fiscal.position'].create({
+                        'name': 'Super Fiscal Position',
+                        'auto_apply': True,
+                        'country_id': self.fiscal_country.id,
+                    })
+                    self.env['account.fiscal.position.tax'].create({
+                        'position_id': fiscal_position.id,
+                        'tax_src_id': self.tax_15.id,
+                        'tax_dest_id': self.tax_10.id,
+                    })
+                    self.env.user.partner_id.country_id = self.fiscal_country
+
+                # define the website pricelist
+                current_website = self.env['website'].get_current_website()
+                pricelist = current_website.get_current_pricelist()
+                pricelist.currency_id = self.product.currency_id
+                self.env['product.pricelist.item'].create({
+                    'price_discount': 0,
+                    'compute_price': 'formula',
+                    'pricelist_id': pricelist.id,
+                })
+
+                with MockRequest(self.env, website=self.website, website_sale_current_pl=pricelist.id):
+                    contextual_price = self.product._get_contextual_price_tax_selection()
+                    self.WebsiteSaleController.cart_update_json(product_id=self.product.id, add_qty=1)
+                    sale_order = self.website.sale_get_order()
+
+                if show_line_subtotals_tax_selection == 'tax_included':
+                    self.assertAlmostEqual(sale_order.amount_total, contextual_price)
+                else:
+                    self.assertAlmostEqual(sale_order.amount_untaxed, contextual_price)