Disable animation on pages

.rubocop.yml

@@ -40,6 +40,9 @@ Metrics/ModuleLength:
 Metrics/PerceivedComplexity:
   Enabled: false
 
+Metrics/ParameterLists:
+  Enabled: false
+
 Lint/UnusedMethodArgument:
   Exclude:
     - 'lib/capybara/driver/base.rb'

History.md

@@ -14,6 +14,8 @@ Release date: unreleased
 * `:element` selector type which will match on any attribute (other than the reserved names) passed as a filter option
 * `:class` filter option now supports preceding class names with `!` to indicate not having that class
 * `:class` and `:id` filter options now accept `XPath::Expression` objects to allow for more flexibility in matching
+* `Capybara.disable_animation` setting which triggers loading of a middleware that attempts to disable animations in pages.
+  This is very much a beta feature and may change/disappear in the future. [Thomas Walpole]
 
 # Version 3.1.1
 Release date: 2018-05-25

lib/capybara/selector.rb

@@ -24,7 +24,6 @@ Capybara::Selector::FilterSet.add(:_field) do
 end
 
 # rubocop:disable Metrics/BlockLength
-# rubocop:disable Metrics/ParameterLists
 
 Capybara.add_selector(:xpath) do
   xpath { |xpath| xpath }
@@ -457,4 +456,3 @@ Capybara.add_selector(:element) do
   end
 end
 # rubocop:enable Metrics/BlockLength
-# rubocop:enable Metrics/ParameterLists

lib/capybara/selector/filter_set.rb

@@ -59,7 +59,7 @@ module Capybara
         options
       end
 
-      def add_filter(name, filter_class, *types, matcher: nil, **options, &block) # rubocop:disable Metrics/ParameterLists
+      def add_filter(name, filter_class, *types, matcher: nil, **options, &block)
         types.each { |k| options[k] = true }
         raise "ArgumentError", ":default option is not supported for filters with a :matcher option" if matcher && options[:default]
         if filter_class <= Filters::ExpressionFilter

lib/capybara/server.rb

@@ -3,56 +3,11 @@
 require 'uri'
 require 'net/http'
 require 'rack'
+require 'capybara/server/middleware'
+require 'capybara/server/animation_disabler'
 
 module Capybara
   class Server
-    class Middleware
-      class Counter
-        attr_reader :value
-
-        def initialize
-          @value = 0
-          @mutex = Mutex.new
-        end
-
-        def increment
-          @mutex.synchronize { @value += 1 }
-        end
-
-        def decrement
-          @mutex.synchronize { @value -= 1 }
-        end
-      end
-
-      attr_accessor :error
-
-      def initialize(app, server_errors)
-        @app = app
-        @counter = Counter.new
-        @server_errors = server_errors
-      end
-
-      def pending_requests?
-        @counter.value.positive?
-      end
-
-      def call(env)
-        if env["PATH_INFO"] == "/__identify__"
-          [200, {}, [@app.object_id.to_s]]
-        else
-          @counter.increment
-          begin
-            @app.call(env)
-          rescue *@server_errors => e
-            @error ||= e
-            raise e
-          ensure
-            @counter.decrement
-          end
-        end
-      end
-    end
-
     class << self
       def ports
         @ports ||= {}
@@ -61,9 +16,10 @@ module Capybara
 
     attr_reader :app, :port, :host
 
-    def initialize(app, *deprecated_options, port: Capybara.server_port, host: Capybara.server_host, reportable_errors: Capybara.server_errors)
+    def initialize(app, *deprecated_options, port: Capybara.server_port, host: Capybara.server_host, reportable_errors: Capybara.server_errors, extra_middleware: [])
       warn "Positional arguments, other than the application, to Server#new are deprecated, please use keyword arguments" unless deprecated_options.empty?
       @app = app
+      @extra_middleware = extra_middleware
       @server_thread = nil # suppress warnings
       @host = deprecated_options[1] || host
       @reportable_errors = deprecated_options[2] || reportable_errors
@@ -147,7 +103,7 @@ module Capybara
     end
 
     def middleware
-      @middleware ||= Middleware.new(app, @reportable_errors)
+      @middleware ||= Middleware.new(app, @reportable_errors, @extra_middleware)
     end
 
     def port_key

lib/capybara/server/animation_disabler.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+module Capybara
+  class Server
+    class AnimationDisabler
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        @status, @headers, @body = @app.call(env)
+        return [@status, @headers, @body] unless html_content?
+        response = Rack::Response.new([], @status, @headers)
+
+        @body.each { |html| response.write insert_disable(html) }
+        @body.close if @body.respond_to?(:close)
+
+        response.finish
+      end
+
+    private
+
+      def html_content?
+        !!(@headers["Content-Type"] =~ /html/)
+      end
+
+      def insert_disable(html)
+        html.sub(%r{(</head>)}, DISABLE_MARKUP + '\\1')
+      end
+
+      DISABLE_MARKUP = <<~HTML
+        <script defer>(typeof jQuery !== 'undefined') && (jQuery.fx.off = true);</script>
+        <style>
+          * {
+             transition: none !important;
+             animation-duration: 0s !important;
+             animation-delay: 0s !important;
+          }
+        </style>
+      HTML
+    end
+  end
+end

lib/capybara/server/middleware.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Capybara
+  class Server
+    class Middleware
+      class Counter
+        attr_reader :value
+
+        def initialize
+          @value = 0
+          @mutex = Mutex.new
+        end
+
+        def increment
+          @mutex.synchronize { @value += 1 }
+        end
+
+        def decrement
+          @mutex.synchronize { @value -= 1 }
+        end
+      end
+
+      attr_accessor :error
+
+      def initialize(app, server_errors, extra_middleware = [])
+        @app = app
+        @extended_app = extra_middleware.inject(@app) do |ex_app, klass|
+          klass.new(ex_app)
+        end
+        @counter = Counter.new
+        @server_errors = server_errors
+      end
+
+      def pending_requests?
+        @counter.value.positive?
+      end
+
+      def call(env)
+        if env["PATH_INFO"] == "/__identify__"
+          [200, {}, [@app.object_id.to_s]]
+        else
+          @counter.increment
+          begin
+            @extended_app.call(env)
+          rescue *@server_errors => e
+            @error ||= e
+            raise e
+          ensure
+            @counter.decrement
+          end
+        end
+      end
+    end
+  end
+end

lib/capybara/session.rb

@@ -84,7 +84,9 @@ module Capybara
         yield config
       end
       @server = if config.run_server && @app && driver.needs_server?
-        Capybara::Server.new(@app, port: config.server_port, host: config.server_host, reportable_errors: config.server_errors).boot
+        server_options = { port: config.server_port, host: config.server_host, reportable_errors: config.server_errors }
+        server_options[:extra_middleware] = [Capybara::Server::AnimationDisabler] if config.disable_animation
+        Capybara::Server.new(@app, server_options).boot
       end
       @touched = false
     end

lib/capybara/session/config.rb

@@ -7,7 +7,7 @@ module Capybara
     OPTIONS = %i[always_include_port run_server default_selector default_max_wait_time ignore_hidden_elements
                  automatic_reload match exact exact_text raise_server_errors visible_text_only
                  automatic_label_click enable_aria_label save_path asset_host default_host app_host
-                 server_host server_port server_errors default_set_options].freeze
+                 server_host server_port server_errors default_set_options disable_animation].freeze
 
     attr_accessor(*OPTIONS)
 
@@ -52,6 +52,8 @@ module Capybara
     #   See {Capybara.configure}
     # @!method default_set_options
     #   See {Capybara.configure}
+    # @!method disable_animation
+    #   See {Capybara.configure}
 
     remove_method :server_host
 
@@ -80,6 +82,12 @@ module Capybara
       @default_host = url
     end
 
+    remove_method :disable_animation=
+    def disable_animation=(bool)
+      warn "Capybara.disable_animation is a beta feature - it may change/disappear in a future point version" if bool
+      @disable_animation = bool
+    end
+
     def initialize_copy(other)
       super
       @server_errors = @server_errors.dup

lib/capybara/spec/spec_helper.rb

@@ -30,6 +30,7 @@ module Capybara
         Capybara.match = :smart
         Capybara.enable_aria_label = false
         Capybara.default_set_options = {}
+        Capybara.disable_animation = false
         reset_threadsafe
       end
 

lib/capybara/spec/views/with_animation.erb

@@ -0,0 +1,46 @@
+
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
+  <head>
+    <meta http-equiv="Content-type" content="text/html; charset=utf-8"/>
+    <title>with_animation</title>
+    <script src="/jquery.js" type="text/javascript" charset="utf-8"></script>
+    <script src="/jquery-ui.js" type="text/javascript" charset="utf-8"></script>
+    <script src="/test.js" type="text/javascript" charset="utf-8"></script>
+    <style>
+      .transition.away {
+          width: 0%;
+      }
+
+      a {
+          display: inline-block;
+          width: 100%;
+          overflow: hidden;
+      }
+
+      a:not(.away) {
+        height: 20px;
+      }
+
+      a.transition {
+        transition: all 3s ease-in-out;
+      }
+
+      @keyframes animation {
+          0%   {height: 20px; width: 100%;}
+          100% {height: 0px; width: 0%;}
+      }
+
+      a.animation.away {
+        animation-name: animation;
+        animation-duration: 3s;
+        animation-fill-mode: forwards;
+      }
+    </style>
+  </head>
+
+  <body id="with_animation">
+    <a href='#' class='transition' onclick='this.classList.add("away")'>transition me away</a>
+    <a href='#' class='animation' onclick='this.classList.add("away")'>animate me away</a>
+  </body>
+</html>
+

spec/shared_selenium_session.rb

@@ -256,6 +256,29 @@ RSpec.shared_examples "Capybara::Session" do |session, mode|
         end.to raise_error(ArgumentError, 'Not allowed to close the primary window')
       end
     end
+
+    context "AnimationDisabler" do
+      before(:context) do # rubocop:disable RSpec/BeforeAfterAll
+        Capybara.disable_animation = true
+        @animation_session = Capybara::Session.new(session.mode, TestApp.new)
+      end
+
+      after(:context) do # rubocop:disable RSpec/BeforeAfterAll
+        Capybara.disable_animation = false
+      end
+
+      it "should disable CSS transitions" do
+        @animation_session.visit('with_animation')
+        @animation_session.click_link('transition me away')
+        expect(@animation_session).to have_no_link('transition me away', wait: 0.5)
+      end
+
+      it "should disable CSS animations", :focus_ do
+        @animation_session.visit('with_animation')
+        @animation_session.click_link('animate me away')
+        expect(@animation_session).to have_no_link('animate me away', wait: 0.5)
+      end
+    end
   end
 
   def headless_or_remote?