[nodriver] implemented automatic event handler propagation for iframes

[xn435]

I've needed to conveniently propagate event handlers to all iframes of the page automatically so I modified nodriver in my fork: xn435/nodriver.

I wanted to open a pull request or create a new discussion in the nodriver repository but only collaborators can do that, so I suppose this is the correct place to do that.

With my changes you can propagate event handlers by simply calling page.propagate_handlers() after adding handlers to the page. If you make changes to the event handlers on the page you will have to call page.propagate_handlers() again if you want those changes to apply to the iframes as well. You can also remove all handlers from the iframes by calling it with an empty dictionary like so: page.propagate_handlers({}).

Usage example

Note: modify the url to something valid which uses iframes.

url = 'https://any.page.with.iframes.example.com/'
wait_time = 10

async def main():
    browser = await uc.start()
    page = browser.main_tab
    page.add_handler(uc.cdp.network.RequestWillBeSent, request_will_be_sent)
    await page.propagate_handlers()
    
    page = await browser.get(url)
    await page.wait(wait_time)


async def request_will_be_sent(event: uc.cdp.network.RequestWillBeSent):
    print('request url: '+event.request.url)

if __name__ == '__main__':
    uc.loop().run_until_complete(main())

Implementation Details and Design Discussion

Figuring out if a target is an iframe child of another target

After reading through chrome devtools protocol for days and trying out different methods to determine if a target is a child target of the page, I finally found a solution. You need to recurse the nodes of the page and check if a node with frame_id is equal to the target_id of the iframe. It works, but it seems strange to me that there is no obvious way to check this in the protocol directly. Maybe someone knows a better way to check if a target is a child target of your target?

On Event Handlers

From a design standpoint I think event handlers of the page should always be applied to all child iframes, as that makes the most sense to me. A function such as propagate_handlers ideally shouldn't be needed at all. In the event handler itself you could check if it's an iframe or not if you want to execute code specific to only the iframes or non-iframes.

However as this is probably a breaking change I implemented it in a way that wouldn't break existing code bases.