This event fires immediately before the Plugin stops running. Plugins are unloaded when disabled, uninstalled, about to be updated, or when the place is closing.

It enables a plugin to clean up after itself before its scripts stop running, e.g. to remove unnecessary instances from the DataModel. If a plugin does not clean up properly, the old copies will remain. When this occurs, users may be forced to close and reopen the place which is a bad user experience.

Plugin-related instances such as PluginToolbarButton|PluginToolbarButtons, DockWidgetPluginGui|DockWidgetPluginGuis, and PluginGui|PluginGuis are automatically cleaned up when the plugin is unloaded so there is no need to remove them.

See also

articles/Intro to Plugins, an introductory article to plugin use and development