feat: add attach to an existing session (#337)

Added a method to attach to an existing session into the driver class so that users can attach to an existing session for debugging. The capabilities only has the given automationName and platformName for the internal use. W3C does not define getting a session info, so we need to give them.
appium · Dec 11, 2022 · 4621549 · 4621549
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,8 @@ Read `release_notes.md` for commit level details.
 ## [Unreleased]
 
 ### Enhancements
+- Add `::Appium::Core::Driver#attach_to` to generate a driver instance which has the given session id.
+    - The primary usage is for debugging to attach to an existing session.
 
 ### Bug fixes
 

diff --git a/README.md b/README.md
@@ -104,7 +104,7 @@ $ IGNORE_VERSION_SKIP=true CI=true bundle exec rake test:func:android
 
     opts = {
       capabilities: { # Append capabilities
-        platformName: :ios,
+        platformName: 'ios',
         platformVersion: '11.0',
         deviceName: 'iPhone Simulator',
         automationName: 'XCUITest',
@@ -133,6 +133,15 @@ $ IGNORE_VERSION_SKIP=true CI=true bundle exec rake test:func:android
 
 More examples are in [test/functional](test/functional)
 
+As of version 5.8.0, the client can attach to an existing session. The main purpose is for debugging.
+
+```ruby
+# @driver is the driver instance of an existing session
+attached_driver = ::Appium::Core::Driver.attach_to @driver.session_id, url: 'http://127.0.0.1:4723/wd/hub', automation_name: 'XCUITest', platform_name: 'ios'
+assert attached_driver.session_id == @driver.session_id
+attached_driver.page_source
+```
+
 ### Capabilities
 
 Read [Appium/Core/Driver](https://www.rubydoc.info/github/appium/ruby_lib_core/Appium/Core/Driver) to catch up with available capabilities.

diff --git a/lib/appium_lib_core/common/base/bridge.rb b/lib/appium_lib_core/common/base/bridge.rb
@@ -43,13 +43,39 @@ class Bridge < ::Selenium::WebDriver::Remote::Bridge
 
         def browser
           @browser ||= begin
-            name = @capabilities.browser_name
+            name = @capabilities&.browser_name
             name ? name.tr(' ', '_').downcase.to_sym : 'unknown'
           rescue KeyError
             APPIUM_NATIVE_BROWSER_NAME
           end
         end
 
+        # Appium only.
+        # Attach to an existing session.
+        #
+        # @param [String] The session id to attach to.
+        # @param [String] platform_name The platform name to keep in the dummy capabilities
+        # @param [String] platform_name The automation name to keep in the dummy capabilities
+        # @return [::Appium::Core::Base::Capabilities]
+        #
+        # @example
+        #
+        #   new_driver = ::Appium::Core::Driver.attach_to(
+        #     driver.session_id,
+        #     url: 'http://127.0.0.1:4723/wd/hub', automation_name: 'UiAutomator2', platform_name: 'Android'
+        #   )
+        #
+        def attach_to(session_id, platform_name, automation_name)
+          @available_commands = ::Appium::Core::Commands::COMMANDS.dup
+          @session_id = session_id
+
+          # generate a dummy capabilities instance which only has the given platformName and automationName
+          @capabilities = ::Appium::Core::Base::Capabilities.new(
+            'platformName' => platform_name,
+            'automationName' => automation_name
+          )
+        end
+
         # Override
         # Creates session handling.
         #

diff --git a/lib/appium_lib_core/common/base/driver.rb b/lib/appium_lib_core/common/base/driver.rb
@@ -59,13 +59,26 @@ def initialize(bridge: nil, listener: nil, **opts)
         # @return [::Appium::Core::Base::Bridge]
         #
         def create_bridge(**opts)
+          # for a new session request
           capabilities = opts.delete(:capabilities)
           bridge_opts = { http_client: opts.delete(:http_client), url: opts.delete(:url) }
+
+          # for attaching to an existing session
+          session_id = opts.delete(:existing_session_id)
+          automation_name = opts.delete(:automation_name)
+          platform_name = opts.delete(:platform_name)
+
           raise ::Appium::Core::Error::ArgumentError, "Unable to create a driver with parameters: #{opts}" unless opts.empty?
 
           bridge = ::Appium::Core::Base::Bridge.new(**bridge_opts)
 
-          bridge.create_session(capabilities)
+          if session_id.nil?
+            bridge.create_session(capabilities)
+          else
+            # attach to the existing session id
+            bridge.attach_to(session_id, platform_name, automation_name)
+          end
+
           bridge
         end
 

diff --git a/lib/appium_lib_core/driver.rb b/lib/appium_lib_core/driver.rb
@@ -275,7 +275,40 @@ class Driver
       #     @core.start_driver # start driver with 'url'. Connect to 'http://custom-host:8080/wd/hub.com'
       #
       def self.for(opts = {})
-        new(opts)
+        new.setup_for_new_session(opts)
+      end
+
+      # Attach to an existing session. The main usage of this method is to attach to
+      # an existing session for debugging. The generated driver instance has the capabilities which
+      # has the given automationName and platformName only since the W3C WebDriver spec does not provide
+      # an endpoint to get running session's capabilities.
+      #
+      #
+      # @param [String] The session id to attach to.
+      # @param [String] url The WebDriver URL to attach to with the session_id.
+      # @param [String] automation_name The platform name to keep in the dummy capabilities
+      # @param [String] platform_name The automation name to keep in the dummy capabilities
+      # @return [Selenium::WebDriver] A new driver instance with the given session id.
+      #
+      # @example
+      #
+      #   new_driver = ::Appium::Core::Driver.attach_to(
+      #     driver.session_id,  # The 'driver' has an existing session id
+      #     url: 'http://127.0.0.1:4723/wd/hub', automation_name: 'UiAutomator2', platform_name: 'Android'
+      #   )
+      #   new_driver.page_source # for example
+      #
+      def self.attach_to(
+        session_id, url: nil, automation_name: nil, platform_name: nil,
+        http_client_ops: { http_client: nil, open_timeout: 999_999, read_timeout: 999_999 }
+      )
+        new.attach_to(
+          session_id,
+          automation_name: automation_name,
+          platform_name: platform_name,
+          url: url,
+          http_client_ops: http_client_ops
+        )
       end
 
       private
@@ -286,20 +319,25 @@ def delegated_target_for_test
         @delegate_target
       end
 
-      public
-
       # @private
-      def initialize(opts = {})
+      def initialize
         @delegate_target = self # for testing purpose
         @automation_name = nil # initialise before 'set_automation_name'
+      end
+
+      public
+
+      # @private
+      # Set up for a neww session
+      def setup_for_new_session(opts = {})
+        @custom_url = opts.delete :url # to set the custom url as :url
 
         # TODO: Remove when we implement Options
         # The symbolize_keys is to keep compatiility for the legacy code, which allows capabilities to give 'string' as the key.
         # The toplevel `caps`, `capabilities` and `appium_lib` are expected to be symbol.
         # FIXME: First, please try to remove `nested: true` to `nested: false`.
         opts = Appium.symbolize_keys(opts, nested: true)
 
-        @custom_url = opts.delete :url
         @caps = get_caps(opts)
 
         set_appium_lib_specific_values(get_appium_lib_opts(opts))
@@ -308,8 +346,7 @@ def initialize(opts = {})
         set_automation_name
 
         extend_for(device: @device, automation_name: @automation_name)
-
-        self # rubocop:disable Lint/Void
+        self
       end
 
       # Creates a new global driver and quits the old one if it exists.
@@ -320,7 +357,7 @@ def initialize(opts = {})
       # @option http_client_ops [Hash] :http_client Custom HTTP Client
       # @option http_client_ops [Hash] :open_timeout Custom open timeout for http client.
       # @option http_client_ops [Hash] :read_timeout Custom read timeout for http client.
-      # @return [Selenium::WebDriver] the new global driver
+      # @return [Selenium::WebDriver] A new driver instance
       #
       # @example
       #
@@ -406,7 +443,47 @@ def start_driver(server_url: nil,
         @driver
       end
 
-      private
+      # @privvate
+      # Attach to an existing session
+      def attach_to(session_id, url: nil, automation_name: nil, platform_name: nil,
+                    http_client_ops: { http_client: nil, open_timeout: 999_999, read_timeout: 999_999 })
+
+        raise ::Appium::Core::Error::ArgumentError, 'The :url must not be nil' if url.nil?
+        raise ::Appium::Core::Error::ArgumentError, 'The :automation_name must not be nil' if automation_name.nil?
+        raise ::Appium::Core::Error::ArgumentError, 'The :platform_name must not be nil' if platform_name.nil?
+
+        @custom_url = url
+
+        # use lowercase internally
+        @automation_name = convert_downcase(automation_name)
+        @device = convert_downcase(platform_name)
+
+        extend_for(device: @device, automation_name: @automation_name)
+
+        @http_client = get_http_client http_client: http_client_ops.delete(:http_client),
+                                       open_timeout: http_client_ops.delete(:open_timeout),
+                                       read_timeout: http_client_ops.delete(:read_timeout)
+
+        # Note that 'enable_idempotency_header' works only a new session reqeust. The attach_to method skips
+        # the new session request, this it does not needed.
+
+        begin
+          # included https://github.com/SeleniumHQ/selenium/blob/43f8b3f66e7e01124eff6a5805269ee441f65707/rb/lib/selenium/webdriver/remote/driver.rb#L29
+          @driver = ::Appium::Core::Base::Driver.new(http_client: @http_client,
+                                                     url: @custom_url,
+                                                     listener: @listener,
+                                                     existing_session_id: session_id,
+                                                     automation_name: automation_name,
+                                                     platform_name: platform_name)
+
+          # export session
+          write_session_id(@driver.session_id, @export_session_path) if @export_session
+        rescue Errno::ECONNREFUSED
+          raise "ERROR: Unable to connect to Appium. Is the server running on #{@custom_url}?"
+        end
+
+        @driver
+      end
 
       def get_http_client(http_client: nil, open_timeout: nil, read_timeout: nil)
         client = http_client || Appium::Core::Base::Http::Default.new
@@ -432,8 +509,6 @@ def set_implicit_wait_by_default(wait)
         {}
       end
 
-      public
-
       # Quits the driver
       # @return [void]
       #
@@ -627,17 +702,20 @@ def set_appium_device
         @device = @caps[:platformName] || @caps['platformName']
         return @device unless @device
 
-        @device = @device.is_a?(Symbol) ? @device.downcase : @device.downcase.strip.intern
+        @device = convert_downcase @device
       end
 
       # @private
       def set_automation_name
         # TODO: check if the Appium.symbolize_keys(opts, nested: false) enoug with this
         candidate = @caps[:automationName] || @caps['automationName']
         @automation_name = candidate if candidate
-        @automation_name = if @automation_name
-                             @automation_name.is_a?(Symbol) ? @automation_name.downcase : @automation_name.downcase.strip.intern
-                           end
+        @automation_name = convert_downcase @automation_name if @automation_name
+      end
+
+      # @private
+      def convert_downcase(value)
+        value.is_a?(Symbol) ? value.downcase : value.downcase.strip.intern
       end
 
       # @private
@@ -651,6 +729,10 @@ def set_automation_name_if_nil
 
       # @private
       def write_session_id(session_id, export_path = '/tmp/appium_lib_session')
+        ::Appium::Logger.warn(
+          '[DEPRECATION] export_session option will be removed. ' \
+          'Please save the session id by yourself with #session_id method like @driver.session_id.'
+        )
         export_path = export_path.tr('/', '\\') if ::Appium::Core::Base.platform.windows?
         File.write(export_path, session_id)
       rescue IOError => e

diff --git a/test/unit/common_test.rb b/test/unit/common_test.rb
@@ -158,7 +158,7 @@ def test_add_appium_prefix_already_have_appium_prefix
         base_caps = Appium::Core::Base::Capabilities.new cap
 
         assert_equal base_caps[:platformName], :ios
-        assert_equal base_caps['platformName'], nil
+        assert_nil base_caps['platformName']
 
         expected = {
           'platformName' => :ios,

diff --git a/test/unit/driver_test.rb b/test/unit/driver_test.rb
@@ -485,5 +485,62 @@ def test_search_context_in_element_class
                      windows_uiautomation: '-windows uiautomation',
                      tizen_uiautomation: '-tizen uiautomation' }, ::Appium::Core::Element::FINDERS)
     end
+
+    def test_attach_to_an_existing_session
+      android_mock_create_session_w3c_direct = lambda do |core|
+        response = {
+          value: {
+            sessionId: '1234567890',
+            capabilities: {
+              platformName: :android,
+              automationName: ENV['APPIUM_DRIVER'] || 'uiautomator2',
+              app: 'test/functional/app/api.apk.zip',
+              platformVersion: '7.1.1',
+              deviceName: 'Android Emulator',
+              appPackage: 'io.appium.android.apis',
+              appActivity: 'io.appium.android.apis.ApiDemos',
+              someCapability: 'some_capability',
+              unicodeKeyboard: true,
+              resetKeyboard: true,
+              directConnectProtocol: 'http',
+              directConnectHost: 'localhost',
+              directConnectPort: '8888',
+              directConnectPath: '/wd/hub'
+            }
+          }
+        }.to_json
+
+        stub_request(:post, 'http://127.0.0.1:4723/wd/hub/session')
+          .to_return(headers: HEADER, status: 200, body: response)
+
+        stub_request(:post, 'http://localhost:8888/wd/hub/session/1234567890/timeouts')
+          .with(body: { implicit: 30_000 }.to_json)
+          .to_return(headers: HEADER, status: 200, body: { value: nil }.to_json)
+
+        driver = core.start_driver
+
+        assert_requested(:post, 'http://127.0.0.1:4723/wd/hub/session', times: 1)
+        assert_requested(:post, 'http://localhost:8888/wd/hub/session/1234567890/timeouts',
+                         body: { implicit: 30_000 }.to_json, times: 1)
+        driver
+      end
+
+      core = ::Appium::Core.for(Caps.android_direct)
+      driver = android_mock_create_session_w3c_direct.call(core)
+
+      attached_driver = ::Appium::Core::Driver.attach_to(
+        driver.session_id,
+        url: 'http://127.0.0.1:4723/wd/hub', automation_name: 'UiAutomator2', platform_name: 'Android'
+      )
+
+      assert_equal driver.session_id, attached_driver.session_id
+      # base session
+      assert driver.respond_to?(:current_activity)
+      assert_equal driver.capabilities['automationName'], ENV['APPIUM_DRIVER'] || 'uiautomator2'
+
+      # to check the extend_for if the new driver instance also has the expected method for Android
+      assert attached_driver.respond_to?(:current_activity)
+      assert_equal attached_driver.capabilities['automationName'], 'UiAutomator2'
+    end
   end
 end