Restore cloned output

packages/apputils/src/instancetracker.ts

@@ -52,6 +52,19 @@ export interface IInstanceTracker<T extends Widget> extends IDisposable {
    */
   readonly size: number;
 
+  /**
+   * A promise that is resolved when the instance tracker has been
+   * restored from a serialized state.
+   *
+   * #### Notes
+   * Most client code will not need to use this, since they can wait
+   * for the whole application to restore. However, if an extension
+   * wants to perform actions during the application restoration, but
+   * after the restoration of another instance tracker, they can use
+   * this promise.
+   */
+  readonly restored: Promise<void>;
+
   /**
    * Find the first widget in the tracker that satisfies a filter function.
    *
@@ -325,7 +338,7 @@ export class InstanceTracker<T extends Widget>
    * multiple instance trackers and, when ready, asks them each to restore their
    * respective widgets.
    */
-  restore(options: InstanceTracker.IRestoreOptions<T>): Promise<any> {
+  async restore(options: InstanceTracker.IRestoreOptions<T>): Promise<any> {
     const { command, registry, state, when } = options;
     const namespace = this.namespace;
     const promises = when
@@ -334,36 +347,25 @@ export class InstanceTracker<T extends Widget>
 
     this._restore = options;
 
-    return Promise.all(promises)
-      .then(([saved]) => {
-        return Promise.all(
-          saved.ids.map((id, index) => {
-            const value = saved.values[index];
-            const args = value && (value as any).data;
-            if (args === undefined) {
-              return state.remove(id);
-            }
-
-            // Execute the command and if it fails, delete the state restore data.
-            return registry
-              .execute(command, args)
-              .catch(() => state.remove(id));
-          })
-        );
+    const [saved] = await Promise.all(promises);
+    const val = await Promise.all(
+      saved.ids.map((id, index) => {
+        const value = saved.values[index];
+        const args = value && (value as any).data;
+        if (args === undefined) {
+          return state.remove(id);
+        }
+
+        // Execute the command and if it fails, delete the state restore data.
+        return registry.execute(command, args).catch(() => state.remove(id));
       })
-      .then(val => {
-        this._restored.resolve(void 0);
-        return val;
-      });
+    );
+    this._restored.resolve(void 0);
+    return val;
   }
 
   /**
    * A promise resolved when the instance tracker has been restored.
-   *
-   * #### Notes
-   * This promise is not exposed on the IInstanceTracker interface.
-   * It is intended to allow for the owner/creator of an instance tracker
-   * to perform additional actions after restoration in specialized use-cases.
    */
   get restored(): Promise<void> {
     return this._restored.promise;

packages/notebook-extension/src/index.ts

@@ -536,7 +536,7 @@ function activateNotebookHandler(
         index: widget.content.index
       }),
       name: widget => `${widget.content.path}:${widget.content.index}`,
-      when: tracker.restored
+      when: tracker.restored // After the notebook widgets (but not contents).
     });
   }