[debug] Lazily update frames of all threads in all-stop mode

When a breakpoint occurs in a thread in all-stop mode, all other
threads have outdated/missing stackframes which means no variables
show up and can be inspected. This fixes the issue by marking each
thread as potentially having "dirty" frames: frames that need to be
re-fetched when the user selects them.

Signed-off-by: Samuel Frylmark <samuel.frylmark@ericsson.com>

packages/debug/src/browser/debug-session.tsx

@@ -93,7 +93,10 @@ export class DebugSession implements CompositeTreeElement {
                 }
             }),
             this.on('stopped', async ({ body }) => {
+                // Update thread list
                 await this.updateThreads(body);
+
+                // Update current thread's frames immediately
                 await this.updateFrames();
             }),
             this.on('thread', ({ body: { reason, threadId } }) => {
@@ -221,6 +224,9 @@ export class DebugSession implements CompositeTreeElement {
         this.fireDidChange();
         if (thread) {
             this.toDisposeOnCurrentThread.push(thread.onDidChanged(() => this.fireDidChange()));
+
+            // If this thread is missing stack frame information, then load that.
+            this.updateFrames();
         }
     }
 
@@ -465,7 +471,7 @@ export class DebugSession implements CompositeTreeElement {
 
     protected async updateFrames(): Promise<void> {
         const thread = this._currentThread;
-        if (!thread || thread.frameCount) {
+        if (!thread || thread.pendingFrameCount || thread.frameCount) {
             return;
         }
         if (this.capabilities.supportsDelayedStackTraceLoading) {

packages/debug/src/browser/model/debug-thread.tsx

@@ -140,7 +140,9 @@ export class DebugThread extends DebugThreadData implements TreeElement {
     }
 
     protected pendingFetch = Promise.resolve<DebugStackFrame[]>([]);
+    protected _pendingFetchCount: number = 0;
     async fetchFrames(levels: number = 20): Promise<DebugStackFrame[]> {
+        this._pendingFetchCount += 1;
         return this.pendingFetch = this.pendingFetch.then(async () => {
             try {
                 const start = this.frameCount;
@@ -149,9 +151,14 @@ export class DebugThread extends DebugThreadData implements TreeElement {
             } catch (e) {
                 console.error(e);
                 return [];
+            } finally {
+                this._pendingFetchCount -= 1;
             }
         });
     }
+    get pendingFrameCount(): number {
+        return this._pendingFetchCount;
+    }
     protected async doFetchFrames(startFrame: number, levels: number): Promise<DebugProtocol.StackFrame[]> {
         try {
             const response = await this.session.sendRequest('stackTrace',