Match a CSS selector within all shadow roots

ByShadow.kt

import org.openqa.selenium.By
import org.openqa.selenium.JavascriptExecutor
import org.openqa.selenium.SearchContext
import org.openqa.selenium.WebElement

class ByShadow(vararg selectors: String) : By() {

    private val args = "['" + selectors.joinToString("','") + "']"

    override fun findElements(ctx: SearchContext): List<WebElement> {
        val result = (ctx as JavascriptExecutor).executeScript("""
            return ((selectors) => {
                'use strict';

                function deepSelect(node, selector) {
                    return Array.from(node.querySelectorAll(selector))
                        .concat(
                            Array.from(node.querySelectorAll('*'))
                                .filter(node => node.shadowRoot)
                                .flatMap(node => deepSelect(node.shadowRoot, selector))
                        );
                }

                return selectors.reduce(
                    (nodes, selector) => nodes
                        .concat(nodes
                            .filter(node => node.shadowRoot)
                            .map(node => node.shadowRoot))
                        .flatMap(node => deepSelect(node, selector)),
                    [document],
                );
            })($args)
        """)

        if (result is List<*> && result.all { el -> el is WebElement }) {
            @Suppress("UNCHECKED_CAST")
            return result as? List<WebElement> ?: emptyList()
        }

        return emptyList()
    }
}

deep-query.js

function deepQuery(node, query) {
  'use strict'
  
  return Array.from(node.querySelectorAll(query))
    .concat(
      Array.from(node.querySelectorAll('*'))
        .filter(node => node.shadowRoot)
        .flatMap(node => deepQuery(node.shadowRoot, query))
    )
}