[lexical-headless] Bug Fix: Use window.happyDOM.close() to ensure proper cleanup

[etrepum]

Description

HappyDOM's Window API uses a strange convention for proper cleanup that the original withDOM implementation missed. Had Claude do the research to track this one down.

Closes #8272

Claude's research

That's the leak. Line 16:

private static [PropertySymbol.browserFrames]: Map<number, IBrowserFrame> = new Map();

This is a static Map on the WindowBrowserContext class — a GC root. Every window created gets added to it at line 105:

browserFrames.set(window[PropertySymbol.internalId], browserFrame);

The only place it gets removed is line 115, inside removeWindowBrowserFrameRelation, which is only called from BrowserWindow[PropertySymbol.destroy](). And destroy() is only called from BrowserFrameFactory.destroyFrame(), which is only reached via happyDOM.close().

So the reference chain that prevents GC is:

WindowBrowserContext (static class, GC root)
  └─ browserFrames Map
       └─ IBrowserFrame (the frame)
            └─ .window → BrowserWindow (the window)
            └─ .page → DetachedBrowserPage
                 └─ .context → DetachedBrowserContext
                      └─ .browser → DetachedBrowser

Every Window ever created stays in this static Map forever unless happyDOM.close() is called. window.close() is a no-op for directly-constructed windows (it only works for window.open() popups), so it never triggers the cleanup.

Test plan

I think it'd be fragile to write tests for this happy-dom implementation detail 🤷 I've also submitted a PR to fix the upstream root cause capricorn86/happy-dom#2121 - if that lands upstream this fix would be unobservable since GC would work as-is even with calling the no-op close

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
lexical	Ready	Preview, Comment	Apr 1, 2026 4:50am
lexical-playground	Ready	Preview, Comment	Apr 1, 2026 4:50am

[etrepum]

Note that the RSS will go up for a while especially if you create a lot of garbage quickly, but it should eventually plateau. That's just how GC languages work (at least when the object graphs are non-trivial).