Accessing elements in the shadow DOM

问题

Is it possible to find elements inside the Shadow DOM with python-selenium?

Example use case:

I have this input with type="date":

<input type="date">

And I'd like to click the date picker button on the right and choose a date from the calendar.

If you would inspect the element in Chrome Developer Tools and expand the shadow-root node of the date input, you would see the button is appearing as:

<div pseudo="-webkit-calendar-picker-indicator" id="picker"></div>

Screenshot demonstrating how it looks in Chrome:

Finding the "picker" button by id results into NoSuchElementException:

>>> date_input = driver.find_element_by_name('bday')
>>> date_input.find_element_by_id('picker')
...
selenium.common.exceptions.NoSuchElementException: Message: no such element

I've also tried to use ::shadow and /deep/ locators as suggested here:

>>> driver.find_element_by_css_selector('input[name=bday]::shadow #picker')
...
selenium.common.exceptions.NoSuchElementException: Message: no such element
>>>
>>> driver.find_element_by_css_selector('input[name=bday] /deep/ #picker')
...
selenium.common.exceptions.NoSuchElementException: Message: no such element

---

Note that I can change the date in the input by sending keys to it:

driver.find_element_by_name('bday').send_keys('01/11/2014')

But, I want to set the date specifically by choosing it from a calendar.

回答1:

There's no way to access the shadow root of native HTML 5 elements.

Not useful in this case, but with Chrome it's possible to access a custom created shadow root:

var root = document.querySelector("#test_button").createShadowRoot();
root.innerHTML = "<button id='inner_button'>Button in button</button"

<button id="test_button"></button>

The root can then be accessed this way:

 var element = document.querySelector("#test_button").shadowRoot;

If you want to automate a click on the inner button with selenium python (chromedriver version 2.14+):

 >>> outer = driver.execute_script('return document.querySelector("#test_button").shadowRoot')
 >>> inner = outer.find_element_by_id("inner_button")
 >>> inner.click()

Update 9 Jun 2015

This is the link to the current Shadow DOM W3C Editor's draft on github:

http://w3c.github.io/webcomponents/spec/shadow/

If you're interested in browsing the blink source code, this is a good starting point.

回答2:

The accepted answer has a drawback, many times the shadow host elements are hidden withing shadow trees that's why the best way to do it is to use the selenium selectors to find the shadow host elements and inject the script just to take the shadow root:

def expand_shadow_element(element):
  shadow_root = driver.execute_script('return arguments[0].shadowRoot', element)
  return shadow_root

#the accepted answer code then becomes 
outer = expand_shadow_element(driver.find_element_by_css_selector("#test_button"))
inner = outer.find_element_by_id("inner_button")
inner.click()

To put this into perspective I just added a testable example with Chrome's download page, clicking the search button needs open 3 nested shadow root elements:

import selenium
from selenium import webdriver
driver = webdriver.Chrome()


def expand_shadow_element(element):
  shadow_root = driver.execute_script('return arguments[0].shadowRoot', element)
  return shadow_root

driver.get("chrome://downloads")
root1 = driver.find_element_by_tag_name('downloads-manager')
shadow_root1 = expand_shadow_element(root1)

root2 = shadow_root1.find_element_by_css_selector('downloads-toolbar')
shadow_root2 = expand_shadow_element(root2)

root3 = shadow_root2.find_element_by_css_selector('cr-search-field')
shadow_root3 = expand_shadow_element(root3)

search_button = shadow_root3.find_element_by_css_selector("#search-button")
search_button.click()

Doing the same using the accepted answer approach has the drawback that it hard-codes the queries, is less readable and you cannot use the intermediary selections for other actions:

search_button = driver.execute_script('return document.querySelector("downloads-manager").shadowRoot.querySelector("downloads-toolbar").shadowRoot.querySelector("cr-search-field").shadowRoot.querySelector("#search-button")')
search_button.click()

来源：https://stackoverflow.com/questions/28911799/accessing-elements-in-the-shadow-dom