Allow to enter a voucher before choosing a subevent

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

@@ -1,7 +1,7 @@
 {% load i18n %}
 {% load eventurl %}
 {% for subev in subevent_list %}
-    <a href="{% eventurl event "presale:event.index" subevent=subev.id cart_namespace=cart_namespace %}"
+    <a href="{% if request.GET.voucher %}{% eventurl event "presale:event.redeem" cart_namespace=cart_namespace %}?voucher={{ request.GET.voucher|urlencode }}&subevent={{ subev.pk }}{% else %}{% eventurl event "presale:event.index" subevent=subev.id cart_namespace=cart_namespace %}{% endif %}"
             class="subevent-row">
         <div class="row">
             <div class="col-md-6">

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

@@ -101,6 +101,12 @@
                     {{ frontpage_text|rich_text }}
                 </div>
             {% endif %}
+
+            {% if request.GET.voucher %}
+                <div class="alert alert-info">
+                    {% trans "Please select a date to redeem your voucher." %}
+                </div>
+            {% endif %}
         {% endif %}
 
         {% if subevent and "year" not in request.GET %}

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

@@ -10,7 +10,13 @@
 
 {% block content %}
     <h2>{% trans "Voucher redemption" %}</h2>
+
     {% if subevent %}
+        {% if request.GET.subevent and subevent.pk|stringformat:"i" != request.GET.subevent %}
+            <div class="alert alert-warning">
+                {% trans "This voucher is valid only for the following specific date and time." %}
+            </div>
+        {% endif %}
         <h3>{{ subevent.name }}</h3>
         {% with ev=subevent %}
             <div class="info-row">