Let plugins decide if events should be processed or not (#5618)

* add wants_process_event to EventMixin

in register_event this function get called and the task is just offload if the plugin returns true

* add tests for wants_process_event

* fix comments for register_event after code changes

* add documentation for EventMixin.wants_process_event

* avoid pre-formatting log messages

---------

Co-authored-by: Oliver Lippert <oliver@lipperts-web.de>

InvenTree/plugin/samples/event/filtered_event_sample.py

@@ -0,0 +1,32 @@
+"""Sample plugin which responds to events."""
+
+import logging
+
+from django.conf import settings
+
+from plugin import InvenTreePlugin
+from plugin.mixins import EventMixin
+
+logger = logging.getLogger('inventree')
+
+
+class FilteredEventPluginSample(EventMixin, InvenTreePlugin):
+    """A sample plugin which provides supports for triggered events."""
+
+    NAME = "FilteredEventPlugin"
+    SLUG = "filteredsampleevent"
+    TITLE = "Triggered by test.event only"
+
+    def wants_process_event(self, event):
+        """Return whether given event should be processed or not."""
+        return event == "test.event"
+
+    def process_event(self, event, *args, **kwargs):
+        """Custom event processing."""
+        print(f"Processing triggered event: '{event}'")
+        print("args:", str(args))
+        print("kwargs:", str(kwargs))
+
+        # Issue warning that we can test for
+        if settings.PLUGIN_TESTING:
+            logger.debug('Event `%s` triggered in sample plugin', event)

InvenTree/plugin/samples/event/test_filtered_event_sample.py

@@ -0,0 +1,52 @@
+"""Unit tests for event_sample sample plugins."""
+
+from django.conf import settings
+from django.test import TestCase
+
+from common.models import InvenTreeSetting
+from plugin import registry
+from plugin.base.event.events import trigger_event
+
+from .filtered_event_sample import logger
+
+
+class FilteredEventPluginSampleTests(TestCase):
+    """Tests for EventPluginSample."""
+
+    def test_run_event(self):
+        """Check if the event is issued."""
+        # Activate plugin
+        config = registry.get_plugin('filteredsampleevent').plugin_config()
+        config.active = True
+        config.save()
+
+        InvenTreeSetting.set_setting('ENABLE_PLUGINS_EVENTS', True, change_user=None)
+
+        # Enable event testing
+        settings.PLUGIN_TESTING_EVENTS = True
+        # Check that an event is issued
+        with self.assertLogs(logger=logger, level="DEBUG") as cm:
+            trigger_event('test.event')
+        self.assertIn('DEBUG:inventree:Event `test.event` triggered in sample plugin', cm[1])
+
+        # Disable again
+        settings.PLUGIN_TESTING_EVENTS = False
+
+    def test_ignore_event(self):
+        """Check if the event is issued."""
+        # Activate plugin
+        config = registry.get_plugin('filteredsampleevent').plugin_config()
+        config.active = True
+        config.save()
+
+        InvenTreeSetting.set_setting('ENABLE_PLUGINS_EVENTS', True, change_user=None)
+
+        # Enable event testing
+        settings.PLUGIN_TESTING_EVENTS = True
+        # Check that an event is issued
+        with self.assertLogs(logger=logger, level="DEBUG") as cm:
+            trigger_event('test.some.other.event')
+        self.assertNotIn('DEBUG:inventree:Event `test.some.other.event` triggered in sample plugin', cm[1])
+
+        # Disable again
+        settings.PLUGIN_TESTING_EVENTS = False