Add kernel monitoring.

Author: Alan Fleming

python/jupyterlab_widgets/src/manager.ts

@@ -112,6 +112,9 @@ export abstract class LabWidgetManager
     super.disconnect();
     this._restoredStatus = false;
   }
+  get disconnected() {
+    return !this._restoredStatus;
+  }
 
   protected async _loadFromKernel(): Promise<void> {
     if (!this.kernel) {
@@ -471,6 +474,11 @@ export class KernelWidgetManager extends LabWidgetManager {
     }
   }
 
+  static existsWithActiveKenel(id: string) {
+    const widgetManager = Private.kernelWidgetManagers.get(id);
+    return !widgetManager?.disconnected;
+  }
+
   _handleKernelStatusChange(
     sender: Kernel.IKernelConnection,
     status: Kernel.Status

python/jupyterlab_widgets/src/plugin.ts

@@ -25,6 +25,7 @@ import { DisposableDelegate } from '@lumino/disposable';
 import { WidgetRenderer } from './renderer';
 
 import {
+  KernelWidgetManager,
   LabWidgetManager,
   WIDGET_VIEW_MIMETYPE,
   WidgetManager,
@@ -103,6 +104,22 @@ function activateWidgetExtension(
   const { commands } = app;
   const trans = (translator ?? nullTranslator).load('jupyterlab_widgets');
 
+  app.serviceManager.kernels.runningChanged.connect((models) => {
+    for (const model of models.running()) {
+      if (
+        model &&
+        model.name === 'python3' &&
+        model.execution_state !== 'starting' &&
+        !KernelWidgetManager.existsWithActiveKenel(model.id)
+      ) {
+        const kernel = app.serviceManager.kernels.connectTo({ model: model });
+        if (kernel.handleComms) {
+          new KernelWidgetManager(kernel);
+        }
+      }
+    }
+  });
+
   if (settingRegistry !== null) {
     settingRegistry
       .load(managerPlugin.id)