Filter settings with app.hasPlugin() (jupyterlab#11938)

* Filter settings menus with `app.hasPlugin`

* Filter in context menu

* Pass `isPluginAvailable`

* Pass app to private function only

* Fix unused import

* Filter in the init list instead

* Add comment about the filtering of plugins

Author: jtpio

packages/apputils-extension/src/settingsplugin.ts

@@ -20,9 +20,17 @@ export const settingsPlugin: JupyterFrontEndPlugin<ISettingRegistry> = {
     const { isDisabled } = PageConfig.Extension;
     const connector = new SettingConnector(app.serviceManager.settings);
 
+    // On startup, check if a plugin is available in the application.
+    // This helps avoid loading plugin files from other lab-based applications
+    // that have placed their schemas next to the JupyterLab schemas. Different lab-based
+    // applications might not have the same set of plugins loaded on the page.
+    // As an example this helps prevent having new toolbar items added by another application
+    // appear in JupyterLab as a side-effect when they are defined via the settings system.
     const registry = new SettingRegistry({
       connector,
-      plugins: (await connector.list('active')).values
+      plugins: (await connector.list('active')).values.filter(value =>
+        app.hasPlugin(value.id)
+      )
     });
 
     // If there are plugins that have schemas that are not in the setting
@@ -32,7 +40,7 @@ export const settingsPlugin: JupyterFrontEndPlugin<ISettingRegistry> = {
     void app.restored.then(async () => {
       const plugins = await connector.list('all');
       plugins.ids.forEach(async (id, index) => {
-        if (isDisabled(id) || id in registry.plugins) {
+        if (!app.hasPlugin(id) || isDisabled(id) || id in registry.plugins) {
           return;
         }