plugin: Make init and applications callbacks optional

src/node/plugin.ts

@@ -55,6 +55,9 @@ export class PluginAPI {
   public async applications(): Promise<Application[]> {
     const apps = new Array<Application>()
     for (const [, p] of this.plugins) {
+      if (!p.applications) {
+        continue
+      }
       const pluginApps = await p.applications()
 
       // Add plugin key to each app.
@@ -86,6 +89,9 @@ export class PluginAPI {
    */
   public mount(r: express.Router): void {
     for (const [, p] of this.plugins) {
+      if (!p.router) {
+        continue
+      }
       r.use(`${p.routerPath}`, p.router())
     }
   }

typings/pluginapi.d.ts

@@ -129,8 +129,10 @@ export interface Plugin {
    * Returns the plugin's router.
    *
    * Mounted at <code-sever-root>/<plugin-path>
+   *
+   * If not present, the plugin provides no routes.
    */
-  router(): express.Router
+  router?(): express.Router
 
   /**
    * code-server uses this to collect the list of applications that
@@ -139,8 +141,10 @@ export interface Plugin {
    * refresh the list of applications
    *
    * Ensure this is as fast as possible.
+   *
+   * If not present, the plugin provides no applications.
    */
-  applications(): Application[] | Promise<Application[]>
+  applications?(): Application[] | Promise<Application[]>
 }
 
 /**