Iterate

Author: martinRenou

packages/voila/src/manager.ts

@@ -202,29 +202,42 @@ export class WidgetManager extends JupyterLabManager {
       { version: '1.0.0' }
     );
 
-    // Send a models request msg
-    initComm.send({method: 'request_states'}, {});
-
-    let [data, buffers]: any = await new Promise(resolve => {
-      initComm.on_msg(msg => {
-        const data = msg['content']['data'];
+    // Fetch widget states
+    let data: any;
+    let buffers: any;
+    try {
+      await new Promise((resolve, reject) => {
+        initComm.on_msg(msg => {
+          data = msg['content']['data'];
+
+          if (data.method != 'update_states') {
+            console.warn(`Unknown ${data.method} message on the Control channel`);
+            return;
+          }
 
-        if (data.method != 'update_states') {
-          console.warn(`Unknown ${data.method} message on the Control channel`);
-          return;
-        }
+          buffers = (msg.buffers || []).map((b: any) => {
+            if (b instanceof DataView) {
+                return b;
+            } else {
+                return new DataView(b instanceof ArrayBuffer ? b : b.buffer);
+            }
+          });
 
-        const buffers = (msg.buffers || []).map((b: any) => {
-          if (b instanceof DataView) {
-              return b;
-          } else {
-              return new DataView(b instanceof ArrayBuffer ? b : b.buffer);
-          }
+          resolve(null);
         });
 
-        resolve([data, buffers]);
+        initComm.on_close(reject);
+
+        // Send a states request msg
+        initComm.send({method: 'request_states'}, {});
       });
-    });
+    }
+    catch {
+      console.warn('Failed to open "jupyter.widget.control" comm channel, fallback to slow fetching of widgets.');
+      // TODO Fallback to the old implementation for old ipywidgets versions
+      // return this._build_models_slow();
+      return {};
+    }
 
     initComm.close();
 
@@ -242,6 +255,7 @@ export class WidgetManager extends JupyterLabManager {
 
     const widgetPromises: Promise<base.WidgetModel>[] = [];
 
+    // Start creating all widgets
     for (const widget_id in states) {
       const state = states[widget_id];
 
@@ -273,6 +287,7 @@ export class WidgetManager extends JupyterLabManager {
       }
     }
 
+    // Wait for widgets to be created
     const widgets = await Promise.all(widgetPromises);
     for (const model of widgets) {
       models[model.model_id] = model;