Widget: Pass cart IDs around in some more places

src/pretix/presale/views/cart.py

@@ -47,6 +47,9 @@ class CartActionMixin:
             u += '&require_cookie=true'
         else:
             u += '?require_cookie=true'
+        if 'iframe' in self.request.GET:
+            cart_id = get_or_create_cart_id(self.request)
+            u += '&cart_id={}'.format(cart_id)
         return u
 
     def get_success_url(self, value=None):

src/pretix/presale/views/checkout.py

@@ -1,3 +1,5 @@
+from urllib.parse import quote
+
 from django.contrib import messages
 from django.http import Http404
 from django.shortcuts import redirect
@@ -30,11 +32,11 @@ class CheckoutView(View):
 
         if not cart_exists(request) and "async_id" not in request.GET:
             messages.error(request, _("Your cart is empty"))
-            return redirect(self.get_index_url(self.request))
+            return self.redirect(self.get_index_url(self.request))
 
         if not request.event.presale_is_running:
             messages.error(request, _("The presale for this event is over or has not yet started."))
-            return redirect(self.get_index_url(self.request))
+            return self.redirect(self.get_index_url(self.request))
 
         cart_error = None
         try:
@@ -49,14 +51,13 @@ class CheckoutView(View):
                 continue
             if step.requires_valid_cart and cart_error:
                 messages.error(request, str(cart_error))
-                return redirect(previous_step.get_step_url(request) if previous_step
-                                else self.get_index_url(request))
+                return self.redirect(previous_step.get_step_url(request) if previous_step else self.get_index_url(request))
 
             if 'step' not in kwargs:
-                return redirect(step.get_step_url(request))
+                return self.redirect(step.get_step_url(request))
             is_selected = (step.identifier == kwargs.get('step', ''))
             if "async_id" not in request.GET and not is_selected and not step.is_completed(request, warn=not is_selected):
-                return redirect(step.get_step_url(request))
+                return self.redirect(step.get_step_url(request))
             if is_selected:
                 if request.method.lower() in self.http_method_names:
                     handler = getattr(step, request.method.lower(), self.http_method_not_allowed)
@@ -68,3 +69,8 @@ class CheckoutView(View):
                 step.c_is_before = True
                 step.c_resolved_url = step.get_step_url(request)
         raise Http404()
+
+    def redirect(self, url):
+        if 'cart_id' in self.request.GET:
+            url += ('&' if '?' in url else '?') + 'cart_id=' + quote(self.request.GET.get('cart_id'))
+        return redirect(url)

src/pretix/presale/views/event.py

@@ -10,6 +10,7 @@ from django.core.exceptions import PermissionDenied
 from django.db.models import Count, Prefetch, Q
 from django.http import Http404, HttpResponse
 from django.shortcuts import get_object_or_404, redirect
+from django.urls import reverse
 from django.utils.decorators import method_decorator
 from django.utils.timezone import now
 from django.utils.translation import pgettext_lazy, ugettext_lazy as _
@@ -176,7 +177,12 @@ class EventIndex(EventViewMixin, CartMixin, TemplateView):
     template_name = "pretixpresale/event/index.html"
 
     def get(self, request, *args, **kwargs):
+        from pretix.presale.views.cart import get_or_create_cart_id
+
         self.subevent = None
+        if request.GET.get('src', '') == 'widget' and 'take_cart_id' in request.GET:
+            get_or_create_cart_id(request)
+            return redirect(reverse('presale:event.index', kwargs=kwargs))
         if request.event.has_subevents:
             if 'subevent' in kwargs:
                 self.subevent = request.event.subevents.filter(pk=kwargs['subevent'], active=True).first()