TaxRules: Add internal_name and keep_gross_if_rate_changes (#2422)

Co-authored-by: ser8phin <eva.wolkwitz@gmx.de>

src/tests/presale/test_checkout.py

@@ -351,6 +351,42 @@ class CheckoutTestCase(BaseCheckoutTestCase, TestCase):
             ia = InvoiceAddress.objects.get(pk=self.client.session['carts'][self.session_key].get('invoice_address'))
         assert not ia.vat_id_validated
 
+    def test_reverse_charge_keep_gross(self):
+        self.tr19.eu_reverse_charge = True
+        self.tr19.keep_gross_if_rate_changes = True
+        self.tr19.home_country = Country('DE')
+        self.tr19.save()
+        self.event.settings.invoice_address_vatid = True
+
+        with scopes_disabled():
+            cr1 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+
+        with mock.patch('vat_moss.id.validate') as mock_validate:
+            mock_validate.return_value = ('AT', 'AT123456', 'Foo')
+            self.client.post('/%s/%s/checkout/questions/' % (self.orga.slug, self.event.slug), {
+                'is_business': 'business',
+                'company': 'Foo',
+                'name': 'Bar',
+                'street': 'Baz',
+                'zipcode': '12345',
+                'city': 'Here',
+                'country': 'AT',
+                'vat_id': 'AT123456',
+                'email': 'admin@localhost'
+            }, follow=True)
+
+        cr1.refresh_from_db()
+        assert cr1.price == Decimal('23.00')
+        assert cr1.tax_rate == Decimal('0.00')
+        assert cr1.tax_value == Decimal('0.00')
+
+        with scopes_disabled():
+            ia = InvoiceAddress.objects.get(pk=self.client.session['carts'][self.session_key].get('invoice_address'))
+        assert ia.vat_id_validated
+
     def test_custom_tax_rules(self):
         self.tr19.custom_rules = json.dumps([
             {'country': 'AT', 'address_type': 'business_vat_id', 'action': 'reverse'},
@@ -585,6 +621,72 @@ class CheckoutTestCase(BaseCheckoutTestCase, TestCase):
             cr = CartPosition.objects.get(cart_id=self.session_key)
             assert cr.price == Decimal('21.26')
 
+    def test_free_price_net_price_reverse_charge_keep_gross(self):
+        # This is an end-to-end test of a very confusing case in which the event is set to
+        # "show net prices" but the tax rate is set to "keep gross if rate changes" in
+        # combination of free prices.
+        # This means the user will be greeted with a display price of "23 EUR + VAT". If they
+        # then adjust the price to pay more, e.g. "40 EUR", it will be interpreted as a net
+        # value (since the event is set to shown net values). The cart position is therefore
+        # created with a gross price of 47.60 EUR. Then, the user enters their invoice address, which
+        # triggers reverse charge. The tax is now removed, but since the tax rule is set to
+        # keep the gross price the same, the user will still need to pay 47.60 EUR (incl 0% VAT),
+        # instead of the 40 EUR the maybe wanted in the first place.
+        # While confusing, this behaviour is technically correct and the correct answer to anyone
+        # complaining about this is "do not turn display_net_prices and keep_gross_if_rate_changes
+        # on at the same time" (display_net_prices only makes sense if you're targeting a B2B
+        # audience in which case keep_gross_if_rate_changes is useless or even harmful).
+        self.event.settings.display_net_prices = True
+        self.ticket.free_price = True
+        self.ticket.save()
+        self.tr19.eu_reverse_charge = True
+        self.tr19.keep_gross_if_rate_changes = True
+        self.tr19.price_includes_tax = False
+        self.tr19.home_country = Country('DE')
+        self.tr19.save()
+        self.event.settings.invoice_address_vatid = True
+
+        response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+            'item_%d' % self.ticket.id: '1',
+            'price_%d' % self.ticket.id: '40.00',
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/?require_cookie=true' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+
+        with scopes_disabled():
+            cr1 = CartPosition.objects.get()
+            assert cr1.price == Decimal('47.60')
+            assert cr1.tax_rate == Decimal('19.00')
+
+        with mock.patch('vat_moss.id.validate') as mock_validate:
+            mock_validate.return_value = ('AT', 'AT123456', 'Foo')
+            self.client.post('/%s/%s/checkout/questions/' % (self.orga.slug, self.event.slug), {
+                'is_business': 'business',
+                'company': 'Foo',
+                'name': 'Bar',
+                'street': 'Baz',
+                'zipcode': '12345',
+                'city': 'Here',
+                'country': 'AT',
+                'vat_id': 'AT123456',
+                'email': 'admin@localhost'
+            }, follow=True)
+
+        cr1.refresh_from_db()
+        assert cr1.price == Decimal('47.60')
+        assert cr1.tax_rate == Decimal('0.00')
+
+        self._set_session('payment', 'banktransfer')
+
+        response = self.client.post('/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug), follow=True)
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select(".thank-you")), 1)
+        with scopes_disabled():
+            op = OrderPosition.objects.get()
+            self.assertEqual(op.price, Decimal('47.60'))
+            self.assertEqual(op.tax_value, Decimal('0.00'))
+            self.assertEqual(op.tax_rate, Decimal('0.00'))
+
     def test_question_file_upload(self):
         with scopes_disabled():
             q1 = Question.objects.create(
@@ -1876,6 +1978,46 @@ class CheckoutTestCase(BaseCheckoutTestCase, TestCase):
             cr1 = CartPosition.objects.get(id=cr1.id)
             self.assertEqual(cr1.price, round_decimal(Decimal('24.00') / Decimal('1.19')))
 
+    def test_confirm_price_changed_reverse_charge_keep_gross(self):
+        self._enable_reverse_charge()
+        self.tr19.keep_gross_if_rate_changes = True
+        self.tr19.save()
+        self.ticket.default_price = 24
+        self.ticket.save()
+        with scopes_disabled():
+            cr1 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() - timedelta(minutes=10)
+            )
+        self._set_session('payment', 'banktransfer')
+
+        response = self.client.post('/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug), follow=True)
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select(".alert-danger")), 1)
+        with scopes_disabled():
+            cr1 = CartPosition.objects.get(id=cr1.id)
+        self.assertEqual(cr1.price, Decimal('24.00'))
+
+    def test_confirm_price_not_changed_reverse_charge_keep_gross(self):
+        self._enable_reverse_charge()
+        self.tr19.keep_gross_if_rate_changes = True
+        self.tr19.save()
+        with scopes_disabled():
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() - timedelta(minutes=10)
+            )
+        self._set_session('payment', 'banktransfer')
+
+        response = self.client.post('/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug), follow=True)
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select(".thank-you")), 1)
+        with scopes_disabled():
+            op = OrderPosition.objects.get()
+            self.assertEqual(op.price, Decimal('23.00'))
+            self.assertEqual(op.tax_value, Decimal('0.00'))
+            self.assertEqual(op.tax_rate, Decimal('0.00'))
+
     def test_confirm_price_changed(self):
         self.ticket.default_price = 24
         self.ticket.save()