Add new signal nav_item

doc/development/api/general.rst

@@ -45,7 +45,7 @@ Backend
 
 .. automodule:: pretix.control.signals
    :members: nav_event, html_head, html_page_start, quota_detail_html, nav_topbar, nav_global, nav_organizer, nav_event_settings,
-             order_info, event_settings_widget, oauth_application_registered, order_position_buttons
+             order_info, event_settings_widget, oauth_application_registered, order_position_buttons, nav_item
 
 
 .. automodule:: pretix.base.signals

src/pretix/control/signals.py

@@ -237,6 +237,24 @@ As with all plugin signals, the ``sender`` keyword argument will contain the eve
 A second keyword argument ``request`` will contain the request object.
 """
 
+nav_item = EventPluginSignal(
+    providing_args=['request', 'item']
+)
+"""
+This signal is sent out to include tab links on the settings page of an item.
+Receivers are expected to return a list of dictionaries. The dictionaries
+should contain at least the keys ``label`` and ``url``. You should also return
+an ``active`` key with a boolean set to ``True``, when this item should be marked
+as active.
+
+If your linked view should stay in the tab-like context of this page, we recommend
+that you use ``pretix.control.views.item.ItemDetailMixin`` for your view
+and your template inherits from ``pretixcontrol/item/base.html``.
+
+As with all plugin signals, the ``sender`` keyword argument will contain the event.
+A second keyword argument ``request`` will contain the request object.
+"""
+
 event_settings_widget = EventPluginSignal(
     providing_args=['request']
 )

src/pretix/control/templates/pretixcontrol/item/base.html

@@ -27,6 +27,13 @@
                     {% trans "Bundled products" %}
                 </a>
             </li>
+            {% for n in extra_nav %}
+                <li {% if n.active %}class="active"{% endif %}>
+                    <a href="{{ n.url }}">
+                        {{ n.label }}
+                    </a>
+                </li>
+            {% endfor %}
         </ul>
     {% else %}
         <h1>{% trans "Create product" %}</h1>

src/pretix/control/views/item.py

@@ -33,7 +33,7 @@ from pretix.control.forms.item import (
 from pretix.control.permissions import (
     EventPermissionRequiredMixin, event_permission_required,
 )
-from pretix.control.signals import item_forms
+from pretix.control.signals import item_forms, nav_item
 
 from . import ChartContainingView, CreateView, PaginationMixin, UpdateView
 
@@ -782,6 +782,18 @@ class ItemDetailMixin(SingleObjectMixin):
     model = Item
     context_object_name = 'item'
 
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        nav = sorted(
+            sum(
+                (list(a[1]) for a in nav_item.send(self.request.event, request=self.request, item=self.get_object())),
+                []
+            ),
+            key=lambda r: str(r['label'])
+        )
+        ctx['extra_nav'] = nav
+        return ctx
+
     def get_object(self, queryset=None) -> Item:
         try:
             if not hasattr(self, 'object') or not self.object: