[A11y] Form JavaScript: Support for <button formnovalidate>

* Payment step: Allow to postpone payment choice on some sales channels

* Add tests

* handle payment provider (de-)selection and partial payments (#6526)

---------

Co-authored-by: Lukas Bockstaller <bockstaller@pretix.eu>

package-lock.json

@@ -3380,9 +3380,9 @@
       }
     },
     "node_modules/postcss-selector-parser": {
-      "version": "7.1.5",
-      "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-7.1.5.tgz",
-      "integrity": "sha512-KvvtD7SrlBP7dlgkBghEE3r84CABm5SmV2aNcG4oCA+qDnJ/tvKonFVvwWAyyWUEwxuNawdfEAZKP9zM3oZ2Uw==",
+      "version": "7.1.1",
+      "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-7.1.1.tgz",
+      "integrity": "sha512-orRsuYpJVw8LdAwqqLykBj9ecS5/cRHlI5+nvTo8LcCKmzDmqVORXtOIYEEQuL9D4BxtA1lm5isAqzQZCoQ6Eg==",
       "dev": true,
       "license": "MIT",
       "dependencies": {

src/pretix/base/forms/questions.py

@@ -899,7 +899,7 @@ class BaseQuestionsForm(forms.Form):
             field.widget.attrs['data-question-dependency-values'] = escapejson_attr(json.dumps(q.dependency_values))
             if q.type != 'M':
                 field.widget.attrs['required'] = q.required and not self.all_optional
-                field._required = q.required and not self.all_optional
+            field._required = q.required and not self.all_optional
             field.required = False
         return field
 
@@ -1497,7 +1497,8 @@ class BaseInvoiceAddressForm(forms.ModelForm):
             pass  # Skip re-validation if it is validated
         elif self.validate_vat_id and vat_id_applicable:
             try:
-                normalized_id = validate_vat_id(data.get('vat_id'), str(data.get('country')))
+                requester_id = self.request.event.settings.invoice_address_from_vat_id
+                normalized_id = validate_vat_id(data.get('vat_id'), str(data.get('country')), requester_id)
                 self.instance.vat_id_validated = bool(normalized_id)
                 self.instance.vat_id = data['vat_id'] = normalized_id
             except VATIDFinalError as e:

src/pretix/base/models/orders.py

@@ -626,47 +626,14 @@ class Order(LockModel, LoggedModel):
         self.save(update_fields=['last_modified'])
 
     def set_expires(self, now_dt=None, subevents=None):
-        now_dt = now_dt or now()
-        tz = ZoneInfo(self.event.settings.timezone)
+        from pretix.base.services.payment import compute_payment_deadline
 
-        sales_channel_suffix = "_" + self.sales_channel.identifier.replace(".", "_")
-        if not (mode := self.event.settings.get(f'payment_term_mode{sales_channel_suffix}')):
-            mode = self.event.settings.get('payment_term_mode')
-            sales_channel_suffix = ""
-
-        if mode == 'days':
-            exp_by_date = now_dt.astimezone(tz) + timedelta(days=self.event.settings.get(f'payment_term_days{sales_channel_suffix}', as_type=int))
-            exp_by_date = exp_by_date.astimezone(tz).replace(hour=23, minute=59, second=59, microsecond=0)
-            if self.event.settings.get('payment_term_weekdays'):
-                if exp_by_date.weekday() == 5:
-                    exp_by_date += timedelta(days=2)
-                elif exp_by_date.weekday() == 6:
-                    exp_by_date += timedelta(days=1)
-        elif mode == 'minutes':
-            exp_by_date = now_dt.astimezone(tz) + timedelta(minutes=self.event.settings.get(f'payment_term_minutes{sales_channel_suffix}', as_type=int))
-        else:
-            raise ValueError("'payment_term_mode' has an invalid value '{}'.".format(mode))
-
-        self.expires = exp_by_date
-
-        term_last = self.event.settings.get('payment_term_last', as_type=RelativeDateWrapper)
-        if term_last:
-            if self.event.has_subevents and subevents:
-                terms = [
-                    term_last.datetime(se).date()
-                    for se in subevents
-                ]
-                if not terms:
-                    return
-                term_last = min(terms)
-            else:
-                term_last = term_last.datetime(self.event).date()
-            term_last = make_aware(datetime.combine(
-                term_last,
-                time(hour=23, minute=59, second=59)
-            ), tz)
-            if term_last < self.expires:
-                self.expires = term_last
+        self.expires = compute_payment_deadline(
+            event=self.event,
+            sales_channel=self.sales_channel,
+            now_dt=now_dt,
+            subevents=subevents,
+        )
 
     @cached_property
     def tax_total(self):

src/pretix/base/services/cart.py

@@ -1605,6 +1605,7 @@ def add_payment_to_cart_session(cart_session, provider, min_value: Decimal=None,
         'max_value': str(max_value) if max_value is not None else None,
         'info_data': info_data or {},
     })
+    cart_session['payments_postpone'] = False
 
 
 def add_payment_to_cart(request, provider, min_value: Decimal=None, max_value: Decimal=None, info_data: dict=None):

src/pretix/base/services/orders.py

@@ -961,7 +961,7 @@ def _check_positions(event: Event, now_dt: datetime, time_machine_now_dt: dateti
 
 
 def _apply_rounding_and_fees(positions: List[CartPosition], payment_requests: List[dict], address: InvoiceAddress,
-                             meta_info: dict, event: Event, require_approval=False):
+                             meta_info: dict, event: Event, sales_channel: SalesChannel, require_approval=False):
     fees = []
     # Pre-rounding, pre-fee total is used for fee calculation
     total = sum([c.gross_price_before_rounding for c in positions])
@@ -1021,7 +1021,14 @@ def _apply_rounding_and_fees(positions: List[CartPosition], payment_requests: Li
         payments_assigned += to_pay
         p['payment_amount'] = to_pay
 
-    if total != payments_assigned and not require_approval:
+    allow_postponed_payment = (
+        require_approval or
+        (
+            sales_channel.identifier in event.settings.payment_choice_postpone_allowed_channels and not payment_requests
+        )
+    )
+
+    if total != payments_assigned and not allow_postponed_payment:
         raise OrderError(_("The selected payment methods do not cover the total balance."))
 
     return fees
@@ -1043,7 +1050,15 @@ def _create_order(event: Event, *, email: str, positions: List[CartPosition], no
 
     # Final calculation of fees, also performs final rounding
     try:
-        fees = _apply_rounding_and_fees(positions, payment_requests, address, meta_info, event, require_approval=require_approval)
+        fees = _apply_rounding_and_fees(
+            positions,
+            payment_requests,
+            address,
+            meta_info,
+            event,
+            sales_channel=sales_channel,
+            require_approval=require_approval
+        )
     except TaxRule.SaleNotAllowed:
         raise OrderError(error_messages['country_blocked'])
 

src/pretix/base/services/payment.py

@@ -0,0 +1,76 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020  Raphael Michel and contributors
+# Copyright (C) 2020-today pretix GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+from datetime import datetime, time, timedelta
+from zoneinfo import ZoneInfo
+
+from django.utils.timezone import make_aware, now
+
+from pretix.base.models import Event, SalesChannel
+from pretix.base.reldate import RelativeDateWrapper
+
+
+def compute_payment_deadline(event: Event, sales_channel: SalesChannel, now_dt=None, subevents=None) -> datetime:
+    now_dt = now_dt or now()
+    tz = ZoneInfo(event.settings.timezone)
+
+    sales_channel_suffix = "_" + sales_channel.identifier.replace(".", "_")
+    if not (mode := event.settings.get(f'payment_term_mode{sales_channel_suffix}')):
+        mode = event.settings.get('payment_term_mode')
+        sales_channel_suffix = ""
+
+    if mode == 'days':
+        exp_by_date = now_dt.astimezone(tz) + timedelta(
+            days=event.settings.get(f'payment_term_days{sales_channel_suffix}', as_type=int))
+        exp_by_date = exp_by_date.astimezone(tz).replace(hour=23, minute=59, second=59, microsecond=0)
+        if event.settings.get('payment_term_weekdays'):
+            if exp_by_date.weekday() == 5:
+                exp_by_date += timedelta(days=2)
+            elif exp_by_date.weekday() == 6:
+                exp_by_date += timedelta(days=1)
+    elif mode == 'minutes':
+        exp_by_date = now_dt.astimezone(tz) + timedelta(
+            minutes=event.settings.get(f'payment_term_minutes{sales_channel_suffix}', as_type=int))
+    else:
+        raise ValueError("'payment_term_mode' has an invalid value '{}'.".format(mode))
+
+    expires = exp_by_date
+
+    term_last = event.settings.get('payment_term_last', as_type=RelativeDateWrapper)
+    if term_last:
+        if event.has_subevents and subevents:
+            terms = [
+                term_last.datetime(se).date()
+                for se in subevents
+            ]
+            if not terms:
+                return expires
+            term_last = min(terms)
+        else:
+            term_last = term_last.datetime(event).date()
+        term_last = make_aware(datetime.combine(
+            term_last,
+            time(hour=23, minute=59, second=59)
+        ), tz)
+        if term_last < expires:
+            return term_last
+
+    return expires

src/pretix/base/services/tax.py

@@ -343,6 +343,66 @@ def _validate_vat_id_EU(vat_id, country_code):
         return vat_id
 
 
+def _validate_vat_id_EU_fallback_germany(vat_id, country_code, requester_id):
+    # We can skip most static validation checks because _validate_vat_id_EU always runs before
+    vat_id = normalize_vat_id(vat_id, country_code)
+
+    # The VIES service of the European commission is overused and down due to rate limits A LOT. There is another
+    # API by German BZSt, but it only works if the requester is German and the requested is not.
+    # https://www.bzst.de/DE/Unternehmen/Identifikationsnummern/Umsatzsteuer-Identifikationsnummer/AuslaendischeUSt-IdNr/auslaendische_ust_idnr_node.html
+    try:
+        r = requests.post(
+            "https://api.evatr.vies.bzst.de/app/v1/abfrage",
+            json={
+                "anfragendeUstid": requester_id,
+                "angefragteUstid": vat_id,
+            },
+            timeout=10,
+        )
+        d = r.json()
+        if r.status_code == 200:
+            if d['status'] in ('evatr-0000', 'evatr-2008'):
+                # evatr-0000: Die angefragte Ust-IdNr. ist zum Anfragezeitpunkt gültig.
+                # evatr-2008: Die angefragte Ust-IdNr. ist zum Anfragezeitpunkt gültig.
+                #             Für die qualifizierte Bestätigungsanfrage liegt einer Besonderheit vor.
+                #             Für Rückfragen wenden Sie sich an das BZSt.
+                return vat_id
+            # evatr-2002: Die angefragte USt-IdNr. ist zum Anfragezeitpunkt nicht gültig.
+            #             Sie ist erst gültig ab dem Datum im Feld gueltigAb.
+            # evatr-2006: Die angefragte Ust-IdNr. ist zum Anfragezeitpunkt nicht gültig.
+            #             Sie war gültig im Zeitraum, der durch die Werte in den Feldern gueltigAb und gueltigBis beschrieben ist.
+            raise VATIDFinalError(error_messages['invalid'])
+        elif r.status_code == 400:
+            if d['status'] in ('evatr-0002', 'evatr-0004', 'evatr-0008'):
+                # evatr-0002: Mindestens eins der Pflichtfelder ist nicht besetzt.
+                # evatr-0004: Die anfragende DE Ust-IdNr. ist syntaktisch falsch. Sie passt nicht in das deutsche Erzeugungsschema.
+                # evatr-0008: Die maximale Anzahl von qualifizierten Bestätigungsabfragen für diese Session wurde erreicht.
+                #             Bitte starten Sie erneut mit einer einfachen Bestätigungsabfrage.
+                raise VATIDTemporaryError(error_messages['unavailable'])
+            # evatr-0005: Die angegebene angefragte Ust-IdNr. ist syntaktisch falsch.
+            # evatr-0012: Die angefrage USt-IdNr. ist syntaktisch falsch. Sie passt nicht in das Erzeugungsschema.
+            # evatr-2003: Das angegebene Länderkennzeichen der angefragten USt-IdNr. ist nicht gültig.
+            raise VATIDFinalError(error_messages['invalid'])
+        elif r.status_code == 403:
+            # evatr-0006: Die anfragende DE USt-IdNr. ist nicht berechtigt eine DE Ust-IdNr. anzufragen.
+            # evatr-0007: Fehlerhafter Aufruf.
+            raise VATIDTemporaryError(error_messages['unavailable'])
+        elif r.status_code == 404:
+            if d['status'] in ('evatr-2005'):
+                # evatr-2005: Die angegebene eigene DE Ust-IdNr. ist zum Anfragezeitpunkt nicht gültig.
+                raise VATIDTemporaryError(error_messages['unavailable'])
+            # evatr-2001: Die angefragte USt-IdNr. ist zum Anfragezeitpunkt nicht vergeben.
+            raise VATIDFinalError(error_messages['invalid'])
+        else:  # 500, 503
+            raise VATIDTemporaryError(error_messages['unavailable'])
+    except requests.RequestException:
+        logger.exception('VAT ID checking failed for country {}'.format(country_code))
+        raise VATIDTemporaryError(error_messages['unavailable'])
+    except ValueError:  # JSON parsing failed
+        logger.exception('VAT ID checking failed for country {}'.format(country_code))
+        raise VATIDTemporaryError(error_messages['unavailable'])
+
+
 def _validate_vat_id_CH(vat_id, country_code):
     if vat_id[:3] != 'CHE':
         raise VATIDFinalError(error_messages['country_mismatch'])
@@ -394,12 +454,18 @@ def _validate_vat_id_CH(vat_id, country_code):
         return vat_id
 
 
-def validate_vat_id(vat_id, country_code):
+def validate_vat_id(vat_id, country_code, requester_id=None):
     if not vat_id:
         return vat_id
     country_code = str(country_code)
     if is_eu_country(country_code):
-        return _validate_vat_id_EU(vat_id, country_code)
+        try:
+            return _validate_vat_id_EU(vat_id, country_code)
+        except VATIDTemporaryError:
+            if requester_id and requester_id.startswith("DE") and not vat_id.startswith("DE"):
+                return _validate_vat_id_EU_fallback_germany(vat_id, country_code, requester_id)
+            else:
+                raise
     elif country_code == 'CH':
         return _validate_vat_id_CH(vat_id, country_code)
     elif country_code == 'NO':

src/pretix/base/settings.py

@@ -1159,6 +1159,19 @@ DEFAULTS = {
                         "configured above."),
         )
     },
+    'payment_choice_postpone_allowed_channels': {
+        'default': [],
+        'type': list,
+        'form_class': forms.MultipleChoiceField,
+        'form_kwargs': dict(
+            label=_('Allow postponed payment choice for sales channels'),
+            help_text=_("If postponed payment is allowed on a sales channel, customers can complete their order without "
+                        "selecting a payment method. This is useful whenever orders are not created by the same "
+                        "person who is making the payment."),
+            widget=forms.CheckboxSelectMultiple,
+            choices=[],
+        )
+    },
     'presale_start_show_date': {
         'default': 'True',
         'type': bool,
@@ -1930,8 +1943,6 @@ DEFAULTS = {
         'serializer_class': serializers.BooleanField,
         'form_kwargs': dict(
             label=_("Hide all unavailable dates from calendar or list views"),
-            help_text=_("This option currently only affects the calendar of this event series, not the organizer-wide "
-                        "calendar.")
         )
     },
     'event_calendar_future_only': {

src/pretix/control/forms/event.py

@@ -855,14 +855,21 @@ class PaymentSettingsForm(EventSettingsValidationMixin, SettingsForm):
         'payment_term_accept_late',
         'payment_pending_hidden',
         'payment_explanation',
+        'payment_choice_postpone_allowed_channels',
         'tax_rule_payment',
     ]
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
+        channels = list(self.obj.organizer.sales_channels.all())
+        self.fields['payment_choice_postpone_allowed_channels'].choices = [
+            (c.identifier, c.label) for c in channels
+            if c.type_instance.payment_restrictions_supported
+        ]
+
         self.term_channel_fields = {}
-        for c in self.obj.organizer.sales_channels.all():
+        for c in channels:
             if c.type_instance.payment_restrictions_supported and c.identifier != "web":
                 # At the moment, it seems sufficient to allow this for the same channel types as other payment settings
                 # We can always introduce more flags later if needed

src/pretix/control/templates/pretixcontrol/event/payment.html

@@ -109,6 +109,7 @@
                 {% bootstrap_form_errors form layout="control" %}
                 {% bootstrap_field form.tax_rule_payment layout="control" %}
                 {% bootstrap_field form.payment_explanation layout="control" %}
+                {% bootstrap_field form.payment_choice_postpone_allowed_channels layout="control" %}
             </fieldset>
         </div>
         {% if "event.settings.payment:write" in request.eventpermset %}

src/pretix/control/views/orders.py

@@ -1646,7 +1646,8 @@ class OrderCheckVATID(OrderView):
                 return redirect(self.get_order_url())
 
             try:
-                normalized_id = validate_vat_id(ia.vat_id, str(ia.country))
+                requester_id = self.request.event.settings.invoice_address_from_vat_id
+                normalized_id = validate_vat_id(ia.vat_id, str(ia.country), requester_id)
                 with transaction.atomic():
                     ia.vat_id_validated = True
                     ia.vat_id = normalized_id

src/pretix/presale/checkoutflow.py

@@ -35,6 +35,7 @@ import copy
 import inspect
 import uuid
 from collections import defaultdict
+from datetime import time
 from decimal import Decimal
 
 from django import forms
@@ -52,6 +53,7 @@ from django.shortcuts import redirect
 from django.utils import translation
 from django.utils.functional import cached_property
 from django.utils.html import conditional_escape
+from django.utils.timezone import now
 from django.utils.translation import (
     get_language, gettext_lazy as _, pgettext_lazy,
 )
@@ -71,6 +73,7 @@ from pretix.base.services.cart import (
 from pretix.base.services.cross_selling import CrossSellingService
 from pretix.base.services.memberships import validate_memberships_in_order
 from pretix.base.services.orders import perform_order
+from pretix.base.services.payment import compute_payment_deadline
 from pretix.base.services.pricing import get_price
 from pretix.base.services.tasks import EventTask
 from pretix.base.settings import PERSON_NAME_SCHEMES
@@ -1344,6 +1347,11 @@ class PaymentStep(CartMixin, TemplateFlowStep):
         self.request = request
         self.request.pci_dss_payment_page = True
 
+        if "postpone" in request.POST and self._allow_postpone:
+            self.cart_session['payments_postpone'] = True
+            self.cart_session['payments'] = []
+            return redirect_to_url(self.get_next_url(request))
+
         if "remove_payment" in request.POST:
             self._remove_payment(request.POST["remove_payment"])
             return redirect_to_url(self.get_step_url(request))
@@ -1432,20 +1440,41 @@ class PaymentStep(CartMixin, TemplateFlowStep):
         ctx['providers'] = self.provider_forms
         ctx['show_fees'] = any(p['fee'] for p in self.provider_forms)
 
-        if len(self.provider_forms) == 1:
-            ctx['selected'] = self.provider_forms[0]['provider'].identifier
-        elif 'payment' in self.request.POST:
+        if 'payment' in self.request.POST:
             ctx['selected'] = self.request.POST['payment']
+        elif self.cart_session.get('payments_postpone') and self._allow_postpone:
+            ctx['selected'] = ''
+        elif len(self.provider_forms) == 1:
+            ctx['selected'] = self.provider_forms[0]['provider'].identifier
         elif self.single_use_payment:
             ctx['selected'] = self.single_use_payment['provider']
         else:
             ctx['selected'] = ''
+
+        ctx['allow_postpone'] = self._allow_postpone
+        if self._allow_postpone:
+            now_dt = now()
+            ctx['payment_deadline'] = compute_payment_deadline(
+                event=self.request.event,
+                sales_channel=self.request.sales_channel,
+                subevents={p.subevent for p in ctx['cart']['raw']},
+                now_dt=now_dt,
+            )
+            if ctx['payment_deadline'].time() != time(hour=23, minute=59, second=59):
+                ctx['payment_deadline_minutes'] = int((ctx['payment_deadline'] - now_dt).total_seconds() // 60)
         return ctx
 
+    @cached_property
+    def _allow_postpone(self):
+        return self.request.sales_channel.identifier in self.request.event.settings.payment_choice_postpone_allowed_channels
+
     def _is_allowed(self, prov, request):
         return prov.is_allowed(request, total=self._total_order_value)
 
     def is_completed(self, request, warn=False):
+        if self.cart_session.get('payments_postpone') and self._allow_postpone:
+            return True
+
         if not self.cart_session.get('payments'):
             if warn:
                 messages.error(request, _('Please select a payment method to proceed.'))

src/pretix/presale/templates/pretixpresale/event/checkout_payment.html

@@ -128,6 +128,35 @@
                 {% endif %}
             </div>
         {% endif %}
+        {% if allow_postpone %}
+            <div class="panel panel-default">
+                <div class="panel-body row">
+                    <div class="col-md-9 col-xs-12">
+                        {% trans "Not sure yet? You can complete your order first and then select a payment method later." %}
+                        <br>
+                        <span class="text-muted">
+                            {% if current_payments %}
+                                {% trans "To do so, please first remove the payment methods you already selected above." %}
+                            {% elif payment_deadline_minutes %}
+                                {% blocktrans trimmed with minutes=payment_deadline_minutes %}
+                                    Your payment needs to be completed within {{ minutes }} minutes.
+                                {% endblocktrans %}
+                            {% else %}
+                                {% blocktrans trimmed with deadline=payment_deadline|date:"SHORT_DATE_FORMAT" %}
+                                    Your payment needs to be completed by {{ deadline }}.
+                                {% endblocktrans %}
+                            {% endif %}
+                        </span>
+                    </div>
+                    <div class="col-md-3 col-xs-12 text-right flip">
+                        <button name="postpone" value="on" class="btn btn-primary"
+                                {% if current_payments %}disabled{% endif %}>
+                            {% trans "Proceed without selection" %}
+                        </button>
+                    </div>
+                </div>
+            </div>
+        {% endif %}
         <div class="row checkout-button-row">
             <div class="col-md-4 col-sm-6">
                 <a class="btn btn-block btn-default btn-lg"

src/pretix/presale/views/event.py

@@ -79,7 +79,7 @@ from pretix.presale.signals import seatingframe_html_head
 from pretix.presale.views.organizer import (
     EventListMixin, add_subevents_for_days, days_for_template,
     filter_qs_by_attr, filter_subevents_with_plugins, has_before_after,
-    weeks_for_template,
+    should_hide_subevent, weeks_for_template,
 )
 
 from . import (
@@ -443,12 +443,10 @@ class EventIndex(EventViewMixin, EventListMixin, CartMixin, TemplateView):
                 )
             )
             subevents = filter_subevents_with_plugins(list(subevents), self.request.sales_channel)
-            context['subevent_list'] = subevents
-            if self.request.event.settings.event_list_available_only and not voucher:
-                context['subevent_list'] = [
-                    se for se in subevents
-                    if not se.presale_has_ended and (se.best_availability_state is None or se.best_availability_state >= Quota.AVAILABILITY_RESERVED)
-                ]
+            context['subevent_list'] = [
+                se for se in subevents
+                if not should_hide_subevent(self.request.event.settings, se, voucher)
+            ]
             context['visible_events'] = len(subevents) > 0
         return context
 

src/pretix/presale/views/organizer.py

@@ -601,6 +601,32 @@ def filter_subevents_with_plugins(subevents, sales_channel=None):
     return subevents
 
 
+def should_hide_subevent(settings, subevent, voucher=None):
+    hide = False
+    if settings.event_list_available_only:
+        hide = (
+            # Presale is over → the subevent is not available → hide
+            subevent.presale_has_ended or
+            # Not a single product is available on this sales channel → hide
+            # Note that means there could be products which are ignored for calendar availability (Quota.ignore_for_event_availability)
+            # or products only visible with a voucher. However, for customers with these scenarios, the event_list_available_only
+            # makes only very little sense as it would never do anything, so the flag can just be removed -- or the products should
+            # be made visible so people know why there are no products. In case a voucher is already entered on the calendar view,
+            # this is already respected and subevents are shown correctly.
+            subevent.best_availability_state is None or
+            (
+                # Sold out → hide, unless we have a voucher active that can bypass all quotas
+                (not voucher or not voucher.allow_ignore_quota) and
+                subevent.best_availability_state < Quota.AVAILABILITY_RESERVED
+            )
+        )
+
+    if settings.event_calendar_future_only:
+        if (subevent.date_to or subevent.date_from) < time_machine_now():
+            hide = True
+    return hide
+
+
 def add_subevents_for_days(qs, before, after, ebd, timezones, sales_channel, event=None, cart_namespace=None,
                            voucher=None):
     qs = qs.filter(active=True, is_public=True).filter(
@@ -640,19 +666,8 @@ def add_subevents_for_days(qs, before, after, ebd, timezones, sales_channel, eve
             kwargs['cart_namespace'] = cart_namespace
 
         s = event.settings if event else se.event.settings
-
-        if s.event_list_available_only:
-            hide = se.presale_has_ended or (
-                (not voucher or not voucher.allow_ignore_quota) and
-                se.best_availability_state is not None and
-                se.best_availability_state < Quota.AVAILABILITY_RESERVED
-            )
-            if hide:
-                continue
-
-        if s.event_calendar_future_only:
-            if (se.date_to or se.date_from) < time_machine_now():
-                continue
+        if should_hide_subevent(s, se, voucher):
+            continue
 
         timezones.add(s.timezone)
         tz = ZoneInfo(s.timezone)

src/pretix/presale/views/widget.py

@@ -75,7 +75,7 @@ from pretix.presale.views.cart import get_or_create_cart_id
 from pretix.presale.views.organizer import (
     EventListMixin, add_events_for_days, add_subevents_for_days,
     days_for_template, filter_qs_by_attr, filter_subevents_with_plugins,
-    weeks_for_template,
+    should_hide_subevent, weeks_for_template,
 )
 
 logger = logging.getLogger(__name__)
@@ -757,14 +757,10 @@ class WidgetAPIProductList(EventListMixin, View):
                         evs = evs[:limit]
 
                 tz = request.event.timezone
-                if self.request.event.settings.event_list_available_only:
-                    evs = [
-                        se for se in evs
-                        if not se.presale_has_ended and (
-                            se.best_availability_state is not None and
-                            se.best_availability_state >= Quota.AVAILABILITY_RESERVED
-                        )
-                    ]
+                evs = [
+                    se for se in evs
+                    if not should_hide_subevent(self.request.event.settings, se)
+                ]
 
                 data['events'] = [
                     {

src/pretix/static/pretixpresale/js/ui/main.js

@@ -234,6 +234,7 @@ var form_handlers = function (el) {
 
 function setup_basics(el) {
     el.find("form").attr("novalidate", true).on("submit", function (e) {
+        if (e.originalEvent.submitter.formNoValidate) return;
         if (!this.checkValidity()) {
             var input = this.querySelector(":invalid:not(fieldset)");
             (input.labels[0] || input).scrollIntoView();

src/tests/presale/test_checkout.py

@@ -2372,6 +2372,97 @@ class CheckoutTestCase(BaseCheckoutTestCase, TimemachineTestMixin, TestCase):
             assert p2.fee.value == Decimal("0.46")
             assert o.total == Decimal("25.76")
 
+    def test_payment_postpone_not_allowed(self):
+        self.event.settings.set('payment_banktransfer__enabled', True)
+        with scopes_disabled():
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+        response = self.client.post('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), {
+            'postpone': 'on',
+        }, follow=False)
+        assert 'Please select' in response.content.decode()
+
+    def test_payment_postpone_allowed(self):
+        self.event.settings.set('payment_banktransfer__enabled', True)
+        self.event.settings.payment_choice_postpone_allowed_channels = ['web']
+        with scopes_disabled():
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+        response = self.client.post('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), {
+            'postpone': 'on',
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+
+        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():
+            o = Order.objects.last()
+            assert not o.payments.exists()
+
+    def test_payment_postpone_cleared_on_selection(self):
+        self.event.settings.set('payment_banktransfer__enabled', True)
+        self.event.settings.payment_choice_postpone_allowed_channels = ['web']
+        with scopes_disabled():
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+
+        response = self.client.post('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), {
+            'postpone': 'on',
+        }, follow=False)
+        self.assertRedirects(response, '/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+        assert self.client.session['carts'][self.session_key].get('payments_postpone')
+
+        # The only available provider must not be preselected while the choice is postponed
+        response = self.client.get('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), follow=True)
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select('input[name="payment"]')), 1)
+        self.assertEqual(len(doc.select('input[name="payment"][checked]')), 0)
+
+        # Selecting a payment method takes the order out of the postponed state again
+        response = self.client.post('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), {
+            'payment': 'banktransfer',
+        }, follow=False)
+        self.assertRedirects(response, '/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+        assert not self.client.session['carts'][self.session_key].get('payments_postpone')
+
+    def test_payment_postpone_disabled_with_partial_payment(self):
+        self.event.settings.set('payment_banktransfer__enabled', True)
+        self.event.settings.payment_choice_postpone_allowed_channels = ['web']
+        gc = self.orga.issued_gift_cards.create(currency="EUR")
+        gc.transactions.create(value=20, acceptor=self.orga)
+        with scopes_disabled():
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+
+        response = self.client.get('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), follow=True)
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select('button[name="postpone"]')), 1)
+        self.assertEqual(len(doc.select('button[name="postpone"][disabled]')), 0)
+
+        # Apply a gift card that only covers part of the total
+        response = self.client.post('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), {
+            'payment': 'giftcard',
+            'payment_giftcard-code': gc.secret,
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+
+        # Postponing would silently drop the gift card, so it is no longer offered
+        doc = BeautifulSoup(response.content.decode(), "lxml")
+        self.assertEqual(len(doc.select('button[name="postpone"][disabled]')), 1)
+
     def test_premature_confirm(self):
         response = self.client.get('/%s/%s/checkout/confirm/' % (self.orga.slug, self.event.slug), follow=True)
         self.assertRedirects(response, '/%s/%s/?require_cookie=true' % (self.orga.slug, self.event.slug),