[FIX] point_of_sale: stop showing changes of fiscal position as discount

Current behavior:
When a fiscal position was applied in the PoS, it was considered as a
discount and was shown in the receipt and on the product screen.

Steps to reproduce:
- Create a product with a price of 10€ with 15% tax included in the
  price
- Create a fiscal position that map the 15% tax to 0% tax
- Open a PoS session
- Add the product to the order
- Apply the fiscal position
- The price of the product is now 8.70€ but the order show it as a
  discount of 1.30€ (e.g 10€ -> 8.70€).

opw-3154499

closes odoo/odoo#116918

X-original-commit: d054e7dd2474fad49dab63bf4b2aef09f57780c8
Signed-off-by: Trinh Jacky (trj) <trj@odoo.com>
Signed-off-by: Engels Robin (roen) <roen@odoo.com>

addons/point_of_sale/static/src/js/models.js

@@ -2434,16 +2434,16 @@ export class Orderline extends PosModel {
             return this.get_base_price();
         }
     }
-    get_taxed_lst_unit_price() {
-        var lst_price = this.get_lst_price();
+    get_taxed_lst_unit_price(){
+        var base_price = this.compute_fixed_price(this.get_base_price());
         if (this.pos.config.iface_tax_included === "total") {
             var product = this.get_product();
             var taxes_ids = product.taxes_id;
             var product_taxes = this.pos.get_taxes_after_fp(taxes_ids);
-            return this.compute_all(product_taxes, lst_price, 1, this.pos.currency.rounding)
+            return this.compute_all(product_taxes, base_price, 1, this.pos.currency.rounding)
                 .total_included;
         }
-        return lst_price;
+        return base_price;
     }
     get_price_without_tax() {
         return this.get_all_prices().priceWithoutTax;

addons/point_of_sale/static/tests/tours/ProductScreen.tour.js

@@ -136,6 +136,17 @@ registry.category("web_tour.tours").add("ProductScreenTour", { test: true, url:
 
 startSteps();
 
+ProductScreen.do.clickHomeCategory();
+ProductScreen.do.clickDisplayedProduct('Test Product');
+ProductScreen.check.totalAmountIs('100.00');
+ProductScreen.do.changeFiscalPosition('No Tax');
+ProductScreen.check.noDiscountApplied("100.00");
+ProductScreen.check.totalAmountIs('86.96');
+
+registry.category("web_tour.tours").add("FiscalPositionNoTax", { test: true, url: "/pos/ui", steps: getSteps() });
+
+startSteps();
+
 ProductScreen.do.enterOpeningAmount('90');
 ProductScreen.do.confirmOpeningPopup();
 ProductScreen.check.checkSecondCashClosingDetailsLineAmount('10.00', '-');

addons/point_of_sale/static/tests/tours/helpers/ProductScreenTourMethods.js

@@ -151,6 +151,18 @@ class Do {
             },
         ];
     }
+    changeFiscalPosition(name) {
+        return [
+            {
+                content: 'click fiscal position button',
+                trigger: '.o_fiscal_position_button',
+            },
+            {
+                content: 'fiscal position screen is shown',
+                trigger: `.selection-item:contains("${name}")`,
+            },
+        ];
+    }
 }
 
 class Check {
@@ -262,6 +274,14 @@ class Check {
             },
         ];
     }
+    noDiscountApplied(originalPrice) {
+        return [
+            {
+                content: 'no discount is applied',
+                trigger: `.info:not(:contains(${originalPrice}))`,
+            },
+        ];
+    }
 }
 
 class Execute {

addons/point_of_sale/tests/test_frontend.py

@@ -689,3 +689,44 @@ class TestUi(TestPointOfSaleHttpCommon):
         pos_session = self.main_pos_config.current_session_id
         self.assertEqual(len(pos_session.statement_line_ids), 1)
         self.assertEqual(pos_session.statement_line_ids[0].amount, -10)
+
+    def test_fiscal_position_no_tax(self):
+        #create a tax of 15% with price included
+        tax = self.env['account.tax'].create({
+            'name': 'Tax 15%',
+            'amount': 15,
+            'price_include': True,
+            'amount_type': 'percent',
+            'type_tax_use': 'sale',
+        })
+
+        #create a product with the tax
+        self.product = self.env['product.product'].create({
+            'name': 'Test Product',
+            'taxes_id': [(6, 0, [tax.id])],
+            'list_price': 100,
+            'available_in_pos': True,
+        })
+
+        #create a fiscal position that map the tax to no tax
+        fiscal_position = self.env['account.fiscal.position'].create({
+            'name': 'No Tax',
+            'tax_ids': [(0, 0, {
+                'tax_src_id': tax.id,
+                'tax_dest_id': False,
+            })],
+        })
+
+        pricelist = self.env['product.pricelist'].create({
+            'name': 'Test Pricelist',
+            'discount_policy': 'without_discount',
+        })
+
+        self.main_pos_config.write({
+            'tax_regime_selection': True,
+            'fiscal_position_ids': [(6, 0, [fiscal_position.id])],
+            'available_pricelist_ids': [(6, 0, [pricelist.id])],
+            'pricelist_id': pricelist.id,
+        })
+        self.main_pos_config.open_ui()
+        self.start_tour("/pos/ui?config_id=%d" % self.main_pos_config.id, 'FiscalPositionNoTax', login="accountman")