small optimization of PluginsField serializer

src/pretix/api/serializers/fields.py

@@ -115,10 +115,10 @@ class PluginsField(serializers.Field):
 
     def to_representation(self, obj):
         from pretix.base.plugins import get_all_plugins
-
+        active_plugins = set(obj.get_plugins())
         return sorted([
             p.module for p in get_all_plugins()
-            if not p.name.startswith('.') and getattr(p, 'visible', True) and p.module in obj.get_plugins()
+            if not p.name.startswith('.') and getattr(p, 'visible', True) and p.module in active_plugins
         ])
 
     def to_internal_value(self, data):

src/pretix/base/plugins.py

@@ -49,14 +49,39 @@ class PluginType(Enum):
     EXPORT = 4
 
 
+def plugin_is_available(meta, event=None, organizer=None):
+    if not hasattr(meta.app, 'is_available'):
+        return True
+
+    level = getattr(meta, "level", PLUGIN_LEVEL_EVENT)
+    if level == PLUGIN_LEVEL_EVENT:
+        if event:
+            return meta.app.is_available(event)
+        elif organizer:
+            if not hasattr(organizer, '_plugin_availability_fallback_event'):
+                with scope(organizer=organizer):
+                    setattr(organizer, '_plugin_availability_fallback_event', organizer.events.first())
+            return (
+                organizer._plugin_availability_fallback_event
+                and meta.app.is_available(organizer._plugin_availability_fallback_event)
+            )
+    elif level == PLUGIN_LEVEL_ORGANIZER:
+        if organizer:
+            return meta.app.is_available(organizer)
+        elif event:
+            return meta.app.is_available(event.organizer)
+    elif level == PLUGIN_LEVEL_EVENT_ORGANIZER_HYBRID and (event or organizer):
+        return meta.app.is_available(event or organizer)
+
+    return True
+
+
 def get_all_plugins(*, event=None, organizer=None) -> List[type]:
     """
     Returns the PretixPluginMeta classes of all plugins found in the installed Django apps.
     """
     assert not event or not organizer
     plugins = []
-    event_fallback = None
-    event_fallback_used = False
     for app in apps.get_app_configs():
         if hasattr(app, 'PretixPluginMeta'):
             meta = app.PretixPluginMeta
@@ -65,28 +90,8 @@ def get_all_plugins(*, event=None, organizer=None) -> List[type]:
             if app.name in settings.PRETIX_PLUGINS_EXCLUDE:
                 continue
 
-            level = getattr(meta, "level", PLUGIN_LEVEL_EVENT)
-            if level == PLUGIN_LEVEL_EVENT:
-                if event and hasattr(app, 'is_available'):
-                    if not app.is_available(event):
-                        continue
-                elif organizer and hasattr(app, 'is_available'):
-                    if not event_fallback_used:
-                        with scope(organizer=organizer):
-                            event_fallback = organizer.events.first()
-                        event_fallback_used = True
-                    if not event_fallback or not app.is_available(event_fallback):
-                        continue
-            elif level == PLUGIN_LEVEL_ORGANIZER:
-                if organizer and hasattr(app, 'is_available'):
-                    if not app.is_available(organizer):
-                        continue
-                elif event and hasattr(app, 'is_available'):
-                    if not app.is_available(event.organizer):
-                        continue
-            elif level == PLUGIN_LEVEL_EVENT_ORGANIZER_HYBRID and (event or organizer) and hasattr(app, 'is_available'):
-                if not app.is_available(event or organizer):
-                    continue
+            if not plugin_is_available(meta, event, organizer):
+                continue
 
             plugins.append(meta)
     return sorted(

src/pretix/control/views/organizer.py

@@ -100,7 +100,7 @@ from pretix.base.models.organizer import SalesChannel, TeamAPIToken
 from pretix.base.payment import PaymentException
 from pretix.base.plugins import (
     PLUGIN_LEVEL_EVENT, PLUGIN_LEVEL_EVENT_ORGANIZER_HYBRID,
-    PLUGIN_LEVEL_ORGANIZER,
+    PLUGIN_LEVEL_ORGANIZER, plugin_is_available,
 )
 from pretix.base.services.export import multiexport, scheduled_organizer_export
 from pretix.base.services.mail import mail, prefix_subject
@@ -597,6 +597,13 @@ class OrganizerCreate(CreateView):
         })
 
 
+def available_plugins(organizer):
+    from pretix.base.plugins import get_all_plugins
+
+    return (p for p in get_all_plugins(organizer=organizer) if not p.name.startswith('.')
+            and getattr(p, 'visible', True))
+
+
 class OrganizerPlugins(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixin, TemplateView, SingleObjectMixin):
     model = Organizer
     context_object_name = 'organizer'
@@ -606,12 +613,6 @@ class OrganizerPlugins(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixi
     def get_object(self, queryset=None) -> Organizer:
         return self.request.organizer
 
-    def available_plugins(self, organizer):
-        from pretix.base.plugins import get_all_plugins
-
-        return (p for p in get_all_plugins(organizer=organizer) if not p.name.startswith('.')
-                and getattr(p, 'visible', True))
-
     def prepare_links(self, pluginmeta, key):
         links = getattr(pluginmeta, key, [])
         try:
@@ -637,7 +638,7 @@ class OrganizerPlugins(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixi
         from pretix.base.plugins import CATEGORY_LABELS, CATEGORY_ORDER
 
         context = super().get_context_data(*args, **kwargs)
-        plugins = list(self.available_plugins(self.object))
+        plugins = list(available_plugins(self.object))
 
         active_counter = Counter()
         events_total = 0
@@ -685,7 +686,7 @@ class OrganizerPlugins(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixi
         self.object = self.get_object()
 
         plugins_available = {
-            p.module: p for p in self.available_plugins(self.object)
+            p.module: p for p in available_plugins(self.object)
         }
         choose_events_next = False
         with transaction.atomic():
@@ -786,12 +787,6 @@ class OrganizerPluginEvents(OrganizerDetailViewMixin, OrganizerPermissionRequire
         }
         return kwargs
 
-    def available_plugins(self, organizer):
-        from pretix.base.plugins import get_all_plugins
-
-        return (p for p in get_all_plugins(organizer=organizer) if not p.name.startswith('.')
-                and getattr(p, 'visible', True))
-
     def get_context_data(self, **kwargs):
         return super().get_context_data(
             plugin=self.plugin,
@@ -799,12 +794,10 @@ class OrganizerPluginEvents(OrganizerDetailViewMixin, OrganizerPermissionRequire
         )
 
     def dispatch(self, request, *args, **kwargs):
-        plugins_available = {
-            p.module: p for p in self.available_plugins(self.request.organizer)
-        }
-        if kwargs["plugin"] not in plugins_available:
+        try:
+            self.plugin = next(p for p in available_plugins(self.request.organizer) if p.module == kwargs["plugin"])
+        except StopIteration:
             raise Http404(_("Unknown plugin."))
-        self.plugin = plugins_available[kwargs["plugin"]]
         level = getattr(self.plugin, "level", PLUGIN_LEVEL_EVENT)
         if level == PLUGIN_LEVEL_ORGANIZER:
             raise Http404(_("This plugin can only be enabled for the entire organizer account."))
@@ -835,6 +828,9 @@ class OrganizerPluginEvents(OrganizerDetailViewMixin, OrganizerPermissionRequire
         logentries_to_save = []
 
         for e in self.request.organizer.events.filter(pk__in=events_to_enable):
+            if not plugin_is_available(self.plugin, organizer=self.request.organizer, event=e):
+                messages.warning(self.request, _("This plugin cannot be activated for event {}.").format(e.name))
+                continue
             logentries_to_save.append(
                 e.log_action('pretix.event.plugins.enabled', user=self.request.user, data={'plugin': self.plugin.module}, save=False)
             )