[FIX] point_of_sale: make sure FP is not applied twice on refund

current behavior:
When a product with tax included is sold with a fiscal position that
match the tax to a tax of 0%, then when you refund this order the
fiscal is applied a second time. This result in the 15% tax removed 2
times and the price of the product is incorrect.

steps to reproduce:
- Create a product with 15% tax included
- Create a fiscal position that match the tax to a tax of 0%
- Create a POS with this fiscal position
- Open PoS, and make an order with the product
- Applyy the fiscal position
- Refund the order
- The price of the product is not the same as the one of the original
  order.

opw-3371028

closes odoo/odoo#136348

X-original-commit: 58406515233234ac0ed342d81a5c55886c3b5712
Signed-off-by: Robin Heinz (rhe) <rhe@odoo.com>
Signed-off-by: Robin Engels (roen) <roen@odoo.com>

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

@@ -175,3 +175,35 @@ registry.category("web_tour.tours").add("TicketScreenTour", {
         return getSteps();
     },
 });
+
+
+registry.category("web_tour.tours").add("FiscalPositionNoTaxRefund", {
+    test: true,
+    url: "/pos/ui",
+    steps: () => {
+        startSteps();
+
+        ProductScreen.do.confirmOpeningPopup();
+        ProductScreen.do.clickHomeCategory();
+        ProductScreen.do.clickDisplayedProduct('Product Test');
+        ProductScreen.check.totalAmountIs('100.00');
+        ProductScreen.do.changeFiscalPosition('No Tax');
+        ProductScreen.check.totalAmountIs('86.96');
+        ProductScreen.do.clickPayButton();
+        PaymentScreen.do.clickPaymentMethod('Bank');
+        PaymentScreen.check.remainingIs('0.00');
+        PaymentScreen.do.clickValidate();
+        ReceiptScreen.check.isShown();
+        ReceiptScreen.do.clickNextOrder();
+        ProductScreen.do.clickRefund();
+        TicketScreen.do.selectOrder('-0001');
+        ProductScreen.do.pressNumpad('1');
+        TicketScreen.check.toRefundTextContains('To Refund: 1.00');
+        TicketScreen.do.confirmRefund();
+        ProductScreen.check.isShown();
+        ProductScreen.do.goBackToMainScreen();
+        ProductScreen.check.totalAmountIs('-86.96');
+
+        return getSteps();
+    }
+});

addons/point_of_sale/tests/test_frontend.py

@@ -975,6 +975,49 @@ class TestUi(TestPointOfSaleHttpCommon):
         self.main_pos_config.open_ui()
         self.start_tour("/pos/ui?config_id=%d" % self.main_pos_config.id, 'GS1BarcodeScanningTour', login="accountman")
 
+    def test_refund_order_with_fp_tax_included(self):
+        #create a tax of 15% tax included
+        self.tax1 = self.env['account.tax'].create({
+            'name': 'Tax 1',
+            'amount': 15,
+            'amount_type': 'percent',
+            'type_tax_use': 'sale',
+            'price_include': True,
+        })
+        #create a tax of 0%
+        self.tax2 = self.env['account.tax'].create({
+            'name': 'Tax 2',
+            'amount': 0,
+            'amount_type': 'percent',
+            'type_tax_use': 'sale',
+        })
+        #create a fiscal position with the two taxes
+        self.fiscal_position = self.env['account.fiscal.position'].create({
+            'name': 'No Tax',
+            'tax_ids': [(0, 0, {
+                'tax_src_id': self.tax1.id,
+                'tax_dest_id': self.tax2.id,
+            })],
+        })
+
+        self.product_test = self.env['product.product'].create({
+            'name': 'Product Test',
+            'type': 'product',
+            'available_in_pos': True,
+            'list_price': 100,
+            'taxes_id': [(6, 0, self.tax1.ids)],
+            'categ_id': self.env.ref('product.product_category_all').id,
+        })
+
+        #add the fiscal position to the PoS
+        self.main_pos_config.write({
+            'fiscal_position_ids': [(4, self.fiscal_position.id)],
+            'tax_regime_selection': True,
+            })
+
+        self.main_pos_config.open_ui()
+        self.start_tour("/pos/ui?config_id=%d" % self.main_pos_config.id, 'FiscalPositionNoTaxRefund', login="accountman")
+
 # This class just runs the same tests as above but with mobile emulation
 class MobileTestUi(TestUi):
     browser_size = '375x667'