[BUG] page.waitForSelector() and waitFor: 'attached' not working properly

[thernstig]

Context:

• Playwright Version: 0.15.0
• Operating System: Ubuntu 18.04.4
• Node version: v12.15.0
• Browser: Chromium

Code Snippet

// always works
await page.waitForSelector('lib-table-widget v0-icon', {
  waitFor: 'visible',
});

// never works
await page.waitForSelector('lib-table-widget v0-icon');

Here is the JSPath to the selector:

document.querySelector("body > container").shadowRoot.querySelector("#container > container-layout-holder").shadowRoot.querySelector("#LayoutHolder-app-content > app-content").shadowRoot.querySelector("#AppContent-inner > alarm-viewer").shadowRoot.querySelector("div > lib-dashboard").shadowRoot.querySelector("div > lib-tablwidget > div:nth-child(2) > lib-table").shadowRoot.querySelector("div:nth-child(3) > internal-extended-table").shadowRoot.querySelector("div > table > tbody > tr > td:nth-child(2) > span > span > v0-icon")

Describe the bug

I have no idea, but lately I've been noticing a lot of flakiness with waitForSelector() with its default for waitFor. As in the above case, as the default is waitFor: 'attached', attached surely needs to happen for visible to occur. Still the default does not work. It times out waiting for the element.

[dgozman]

Looking at the code, there is a difference: attached defaults to "poll on mutations", while visible defaults to "poll on rafs". I'll look into fixing this.