[sources] Expand 'Threads' list when pausing in targets other than main

This CL force expands the 'Threads' list if we pause in non-main-frame
targets and the target is different from the previously paused target.

The restriction is to not annoy users that manually close the
'Threads' list and then repeatedly pause e.g. via stepping or hitting
breakpoints multiple times.

[email protected]

Bug: 373893057
Change-Id: I20df41bf0d43f640da62ec2923f8ab28ce26b986
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5952206
Auto-Submit: Simon Zünd <[email protected]>
Commit-Queue: Benedikt Meurer <[email protected]>
Reviewed-by: Benedikt Meurer <[email protected]>

Author: szuend

front_end/panels/sources/SourcesPanel.ts

@@ -206,6 +206,9 @@ export class SourcesPanel extends UI.Panel.Panel implements
   private tabbedLocationHeader?: Element|null;
   private extensionSidebarPanesContainer?: UI.View.ViewLocation;
   sidebarPaneView?: UI.Widget.VBox|UI.SplitWidget.SplitWidget;
+
+  #lastPausedTarget: WeakRef<SDK.Target.Target>|null = null;
+
   constructor() {
     super('sources');
 
@@ -483,6 +486,16 @@ export class SourcesPanel extends UI.Panel.Panel implements
     UI.Context.Context.instance().setFlavor(SDK.DebuggerModel.DebuggerPausedDetails, details);
     this.toggleDebuggerSidebarButton.setEnabled(false);
     this.revealDebuggerSidebar();
+    const pausedTarget = details.debuggerModel.target();
+    if (this.threadsSidebarPane && this.#lastPausedTarget?.deref() !== pausedTarget &&
+        pausedTarget !== SDK.TargetManager.TargetManager.instance().primaryPageTarget()) {
+      // If we pause in something other than the main frame (e.g. worker), we should expand the
+      // "Threads" list to make it more clear which target is paused. We do this only if the target of
+      // the previous pause is different from the new pause to prevent annoying the user by re-opening
+      // the "Threads" list while stepping or hitting the same breakpoint multiple points.
+      void this.sidebarPaneStack?.showView(this.threadsSidebarPane);
+    }
+
     window.focus();
     Host.InspectorFrontendHost.InspectorFrontendHostInstance.bringToFront();
     const withOverlay = UI.Context.Context.instance().flavor(SDK.Target.Target)?.model(SDK.OverlayModel.OverlayModel) &&
@@ -498,6 +511,7 @@ export class SourcesPanel extends UI.Panel.Panel implements
           this.overlayLoggables.stepOverButton, `${VisualLogging.action('debugger.step-over')}`,
           this.overlayLoggables.debuggerPausedMessage);
     }
+    this.#lastPausedTarget = new WeakRef(details.debuggerModel.target());
   }
 
   private maybeLogOverlayAction(): void {

test/e2e/sources/script-in-multiple-workers_test.ts

@@ -118,10 +118,7 @@ describe('Multi-Workers', function() {
 
           // This typically happens too quickly to cause DevTools to switch to the other thread, so
           // click on the other paused thread.
-          await Promise.all([
-            click(THREADS_SELECTOR),
-            waitFor(THREADS_SELECTOR + '[aria-expanded="true"]'),
-          ]);
+          await waitFor(THREADS_SELECTOR + '[aria-expanded="true"]');
           await click('.thread-item:has( .thread-item-paused-state:not(:empty)):not(.selected)');
         });