Support Node#active_element and :focused filter (#261)

As of [teamcapybara/capybara#2489][] (April 14, 2021), Capybara supports
calling `#send_keys` on the page (instead of a particular element).

Similarly, there is a global `:focused` filter that compares the node to
the [Document.activeElement][].

These are both powered by a [Driver#active_element][] method in drivers
that support JavaScript.

This commit integrates `Capybara::Cuprite::Driver` to support both.

[teamcapybara/capybara#2489]: teamcapybara/capybara#2489
[Driver#active_element]: https://github.com/teamcapybara/capybara/blob/c0cbf4024c1abd48b0c22c2930e7b05af58ab284/lib/capybara/driver/base.rb#L62-L68
[Document.activeElement]: https://developer.mozilla.org/en-US/docs/Web/API/Document/activeElement

Author: seanpdoyle

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Added
 
+- Support for `Driver#send_keys`, the `:focused` filter, and `Driver#active_element` [#261]
+
 ### Changed
 - `@window_size` attribute is moved from Ferrum, viewport size is still inherited [#253]
 - Compatibility with latest Ferrum. Browser instance is not passed everywhere now [#254]

lib/capybara/cuprite/browser.rb

@@ -127,6 +127,10 @@ def close_window(target_id)
         targets.delete(target_id) # page.close is async, delete target asap
       end
 
+      def active_element
+        evaluate("document.activeElement")
+      end
+
       def browser_error
         evaluate("_cuprite.browserError()")
       end

lib/capybara/cuprite/driver.rb

@@ -15,6 +15,7 @@ class Driver < Capybara::Driver::Base
       delegate %i[restart quit status_code timeout timeout= current_url title body
                   window_handles close_window switch_to_window within_window window_handle
                   back forward refresh wait_for_reload viewport_size device_pixel_ratio] => :browser
+      delegate %i[send_keys] => :active_element
       alias html body
       alias current_window_handle window_handle
       alias go_back back
@@ -70,6 +71,10 @@ def frame_title
         evaluate_script("document.title")
       end
 
+      def active_element
+        Node.new(self, browser.active_element)
+      end
+
       def find_xpath(selector)
         find(:xpath, selector)
       end

spec/features/driver_spec.rb

@@ -1303,6 +1303,30 @@ def create_screenshot(file, *args)
           expect(input.text).to eq("hello")
         end
 
+        it "supports the :focused filter" do
+          @session.find_field("empty_input").execute_script("this.focus()")
+
+          expect(@session).to have_field("empty_input", focused: true)
+        end
+
+        it "accessed the document.activeElement" do
+          input = @session.find_field("empty_input")
+          input.execute_script("this.focus()")
+
+          expect(@session.active_element).to eq(input)
+        end
+
+        it "sends keys to the active_element" do
+          @session.find_field("empty_input").execute_script("this.focus()")
+
+          expect(@session).to have_field("empty_input", focused: true)
+
+          @session.send_keys(:tab)
+
+          expect(@session).to have_field("empty_input", focused: false)
+            .and(have_field("filled_input", focused: true))
+        end
+
         it "sends keys to filled contenteditable div" do
           input = @session.find(:css, "#filled_div")