Remove ensureSessionReady, use _ready promise

src/service.ts

@@ -1,8 +1,6 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
-import { IClientSession } from '@jupyterlab/apputils';
-
 import { IDisposable } from '@phosphor/disposable';
 
 import { ISignal, Signal } from '@phosphor/signaling';
@@ -307,8 +305,6 @@ export class DebugService implements IDebugger, IDisposable {
     if (!this.session.isStarted) {
       return;
     }
-    // Workaround: this should not be called before the session has started
-    await this.ensureSessionReady();
     if (!path) {
       const dumpedCell = await this.dumpCell(code);
       path = dumpedCell.sourcePath;
@@ -436,8 +432,6 @@ export class DebugService implements IDebugger, IDisposable {
     breakpoints: DebugProtocol.SourceBreakpoint[],
     path: string
   ) => {
-    // Workaround: this should not be called before the session has started
-    await this.ensureSessionReady();
     return await this.session.sendRequest('setBreakpoints', {
       breakpoints: breakpoints,
       source: { path },
@@ -462,11 +456,6 @@ export class DebugService implements IDebugger, IDisposable {
     });
   };
 
-  private async ensureSessionReady(): Promise<void> {
-    const client = this.session.client as IClientSession;
-    return client.ready;
-  }
-
   private clearModel() {
     this._model.callstack.frames = [];
     this._model.variables.scopes = [];

src/session.ts

@@ -62,20 +62,22 @@ export class DebugSession implements IDebugger.ISession {
 
     this._client = client;
 
-    if (client) {
+    if (this._client) {
       this._client.iopubMessage.connect(this._handleEvent, this);
+
+      if (this.client instanceof ClientSession) {
+        this._ready = this.client.ready;
+      } else {
+        this._ready = this.client.kernel.ready;
+      }
     }
   }
 
   /**
    * Return the kernel info for the debug session.
    */
   get kernelInfo(): IDebugger.ISession.IInfoReply | null {
-    const kernel = this.client.kernel;
-    if (!kernel) {
-      return null;
-    }
-    return kernel.info as IDebugger.ISession.IInfoReply;
+    return (this.client.kernel?.info as IDebugger.ISession.IInfoReply) ?? null;
   }
 
   /**
@@ -108,6 +110,7 @@ export class DebugSession implements IDebugger.ISession {
    * Start a new debug session
    */
   async start(): Promise<void> {
+    await this._ready;
     await this.sendRequest('initialize', {
       clientID: 'jupyterlab',
       clientName: 'JupyterLab',
@@ -130,6 +133,7 @@ export class DebugSession implements IDebugger.ISession {
    * Stop the running debug session.
    */
   async stop(): Promise<void> {
+    await this._ready;
     await this.sendRequest('disconnect', {
       restart: false,
       terminateDebuggee: true
@@ -141,11 +145,7 @@ export class DebugSession implements IDebugger.ISession {
    * Restore the state of a debug session.
    */
   async restoreState(): Promise<IDebugger.ISession.Response['debugInfo']> {
-    if (this.client instanceof ClientSession) {
-      await this.client.ready;
-    } else {
-      await this.client.kernel.ready;
-    }
+    await this._ready;
     const message = await this.sendRequest('debugInfo', {});
     this._isStarted = message.body.isStarted;
     return message;
@@ -160,6 +160,7 @@ export class DebugSession implements IDebugger.ISession {
     command: K,
     args: IDebugger.ISession.Request[K]
   ): Promise<IDebugger.ISession.Response[K]> {
+    await this._ready;
     const message = await this._sendDebugMessage({
       type: 'request',
       seq: this._seq++,
@@ -209,6 +210,7 @@ export class DebugSession implements IDebugger.ISession {
   }
 
   private _client: IClientSession | Session.ISession;
+  private _ready: Promise<void>;
   private _disposed = new Signal<this, void>(this);
   private _isDisposed: boolean = false;
   private _isStarted: boolean = false;