Allow to listen for DOM mutations

This for now only implements attribute changes.

rb/build.desc

@@ -291,6 +291,9 @@ ruby_library(name = "devtools",
     ":cdp-v84",
     ":cdp-v85",
     ":cdp-v86"
+  ],
+  resources = [
+    { "../javascript/cdp-support/mutation-listener.js": "rb/lib/selenium/webdriver/atoms/mutationListener.js" }
   ]
 )
 

rb/lib/selenium/webdriver.rb

@@ -25,8 +25,8 @@
 require 'set'
 require 'websocket'
 
-require 'selenium/webdriver/common'
 require 'selenium/webdriver/atoms'
+require 'selenium/webdriver/common'
 require 'selenium/webdriver/version'
 
 module Selenium

rb/lib/selenium/webdriver/common/driver_extensions/has_log_events.rb

@@ -21,7 +21,9 @@ module Selenium
   module WebDriver
     module DriverExtensions
       module HasLogEvents
-        KINDS = %i[console exception].freeze
+        include Atoms
+
+        KINDS = %i[console exception mutation].freeze
 
         #
         # Registers listener to be called whenever browser receives
@@ -43,13 +45,19 @@ module HasLogEvents
         #     exceptions.push(event)
         #   end
         #
-        # @param [Symbol] kind :console or :exception
+        # @example Collect DOM mutations
+        #   mutations = []
+        #   driver.on_log_event(:mutation) do |event|
+        #     mutations.push(event)
+        #   end
+        #
+        # @param [Symbol] kind :console, :exception or :mutation
         # @param [#call] block which is called when event happens
-        # @yieldparam [DevTools::ConsoleEvent, DevTools::ExceptionEvent]
+        # @yieldparam [DevTools::ConsoleEvent, DevTools::ExceptionEvent, DevTools::MutationEvent]
         #
 
         def on_log_event(kind, &block)
-          raise WebDriverError, "Don't know how to handle #{kind} events" unless KINDS.include?(kind)
+          raise Error::WebDriverError, "Don't know how to handle #{kind} events" unless KINDS.include?(kind)
 
           enabled = log_listeners[kind].any?
           log_listeners[kind] << block
@@ -93,6 +101,42 @@ def log_exception_events
           end
         end
 
+        def log_mutation_events
+          devtools.page.enable
+
+          devtools.runtime.add_binding(name: '__webdriver_attribute')
+          execute_script(mutation_listener)
+          script = devtools.page.add_script_to_evaluate_on_new_document(source: mutation_listener)
+          pinned_scripts[mutation_listener] = script['identifier']
+
+          devtools.runtime.on(:binding_called, &method(:log_mutation_event))
+        end
+
+        def log_mutation_event(params)
+          payload = JSON.parse(params['payload'])
+          elements = find_elements(css: "*[data-__webdriver_id='#{payload['target']}']")
+          return if elements.empty?
+
+          event = DevTools::MutationEvent.new(
+            element: elements.first,
+            attribute_name: payload['name'],
+            current_value: payload['value'],
+            old_value: payload['oldValue']
+          )
+
+          log_listeners[:mutation].each do |log_listener|
+            log_listener.call(event)
+          end
+        end
+
+        def mutation_listener
+          @mutation_listener ||= read_atom(:mutationListener)
+        end
+
+        def pinned_scripts
+          @pinned_scripts ||= {}
+        end
+
       end # HasLogEvents
     end # DriverExtensions
   end # WebDriver

rb/lib/selenium/webdriver/devtools.rb

@@ -22,6 +22,7 @@ module WebDriver
     class DevTools
       autoload :ConsoleEvent, 'selenium/webdriver/devtools/console_event'
       autoload :ExceptionEvent, 'selenium/webdriver/devtools/exception_event'
+      autoload :MutationEvent, 'selenium/webdriver/devtools/mutation_event'
 
       SUPPORTED_VERSIONS = [84, 85, 86].freeze
 

rb/lib/selenium/webdriver/devtools/mutation_event.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# Licensed to the Software Freedom Conservancy (SFC) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The SFC licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+module Selenium
+  module WebDriver
+    class DevTools
+      class MutationEvent
+
+        attr_accessor :element, :attribute_name, :current_value, :old_value
+
+        def initialize(element:, attribute_name:, current_value:, old_value:)
+          @element = element
+          @attribute_name = attribute_name
+          @current_value = current_value
+          @old_value = old_value
+        end
+
+      end # MutationEvent
+    end # DevTools
+  end # WebDriver
+end # Selenium

rb/spec/integration/selenium/webdriver/devtools_spec.rb

@@ -95,6 +95,21 @@ module WebDriver
         expect(exception.description).to include('Error: I like cheese')
         expect(exception.stacktrace).not_to be_empty
       end
+
+      it 'notifies about DOM mutations' do
+        mutations = []
+        driver.on_log_event(:mutation) { |mutation| mutations.push(mutation) }
+        driver.navigate.to url_for('dynamic.html')
+
+        driver.find_element(id: 'reveal').click
+        wait.until { mutations.any? }
+
+        mutation = mutations.first
+        expect(mutation.element).to eq(driver.find_element(id: 'revealed'))
+        expect(mutation.attribute_name).to eq('style')
+        expect(mutation.current_value).to eq('')
+        expect(mutation.old_value).to eq('display:none;')
+      end
     end
   end
 end