fix(Playwright): switchTo resolves nested iframes relative to current frame

[DavertMik]

Fixes #5688

Problem

On Playwright, switching into an iframe that is nested inside the current frame left the helper pointing at nothing:

I.amOnPage('/iframe_nested')
I.switchTo('[name=wrapper]')
I.see('Iframe test')         // ok
I.switchTo('[name=content]') // reported as passed
I.see('Information')         // times out

After the second switchTo nothing was reachable any more — not the nested frame, not the parent frame, not the top level. Puppeteer and WebDriver were unaffected, and within({ frame: [...] }) worked, which is why this read as a Playwright-only regression.

Cause

switchTo() built the frame locator from this.page unconditionally:

this.frame = await Promise.race([this.page.frameLocator(locator), ...])

So '[name=content]' was looked up on the top-level document, where it does not exist, and the resulting FrameLocator resolved to nothing.

The failure was silent because the existence check immediately above it goes through _locateElement(), which does honour the current frame. The frame was found, then discarded.

Introduced in cb7efd6 (while removing TestCafe); 3.x chained the locator correctly.

Fix

Chain from the current frame when there is one, as 3.x did:

this.frame = this.frame ? this.frame.frameLocator(locator) : this.page.frameLocator(locator)

The Promise.race wrapper goes away with it: frameLocator() is synchronous, so it never raced anything and left an uncleared 5s timer behind on every switchTo call.

Tests

Three cases added to the shared web API spec, since the behaviour is cross-helper:

• switching into nested iframes one level at a time — fails on 4.x
• switchTo(null) returning to the top level from a nested frame — fails on 4.x
• a nested iframe not being reachable from the top-level context, i.e. switchTo resolves the frame against the current context rather than the page (passes either way; guards the fix from being "fixed" by widening the lookup to the whole document)

Verified locally against Playwright and Puppeteer (#switchTo, plus the full within/iframe/frame set in Playwright_test.js — 43 passing) and against the acceptance within suite (8 passing). WebDriver runs in CI.

🤖 Generated with Claude Code

https://claude.ai/code/session_01M93h8jjpyUt1A7Px3kwpxC