Intercept target creation

In many ways, users want to intercept targets being created to attach and set them up.

Usecases:

• when popup is getting opened, attach to it and enable request interception
• when a link click opens a new page, set proper device emulation before website is getting loaded

We might be able to do this with CDP using Target.setAutoAttach and waitForDebugger option. I’d like this to be scoped to browser context though so that’s there’s a better flexibility.

The API might look like this:

await browserContext.setTargetInterception(true);
browserContext.on('targetcreated', async target => {
  if (target.type() !== 'page') {
    await target.resumeLoading();
    return;
  }
  const page = await target.page();
  await page.setViewport({width: 400, height: 400});
  await target.resumeLoading();
});

Related issues: #1378, #3648

[saberworks]

Is there an ETA on a fix for this? Browsing pages I do not control, I am watching for the targetcreated event in order to inspect popups. When a popup occurs, there doesn’t seem to be any way for me to inspect the network requests. On main page, I can add a handler for request and requestfinished prior to a page.goto which means every network request for that page (even the initial one) can be inspected. However, if I attach request or requestfinished event handlers on the popup page, it’s already too late; the page has already started loading and the events never fire (maybe I’ll see some if the page takes a long time to load a bunch of resources, but never the initial one).

After the fact, I can get the URLs of things that loaded by inspecting the trace file, but it’s difficult to pinpoint only the ones loaded by the popup. In addition, I don’t have access to all the other goodies provided by the Request object (headers, content, etc.).

A fix or any workaround suggestion would be greatly appreciated!

[berstend]

Everyone who’s interested in seeing this fixed: Please star this chromium bug reported by Niek, so the chromium devs know there’s strong interest in getting this resolved - thanks!

https://bugs.chromium.org/p/chromium/issues/detail?id=1070568