Remove BestStandardsSupport middleware

actionpack/lib/action_dispatch.rb

@@ -47,7 +47,6 @@ class IllegalStateError < StandardError
 
   autoload_under 'middleware' do
     autoload :RequestId
-    autoload :BestStandardsSupport
     autoload :Callbacks
     autoload :Cookies
     autoload :DebugExceptions

actionpack/lib/action_dispatch/middleware/best_standards_support.rb

-module ActionDispatch
-  class BestStandardsSupport
-    def initialize(app, type = true)
-      @app = app
-
-      @header = case type
-      when true
-        "IE=Edge,chrome=1"
-      when :builtin
-        "IE=Edge"
-      when false
-        nil
-      end
-    end
-
-    def call(env)
-      status, headers, body = @app.call(env)
-
-      if headers["X-UA-Compatible"] && @header
-        unless headers["X-UA-Compatible"][@header]
-          headers["X-UA-Compatible"] << "," << @header.to_s
-        end
-      else
-        headers["X-UA-Compatible"] = @header
-      end
-
-      [status, headers, body]
-    end
-  end
-end

actionpack/lib/action_dispatch/railtie.rb

@@ -6,7 +6,6 @@ class Railtie < Rails::Railtie # :nodoc:
     config.action_dispatch.x_sendfile_header = nil
     config.action_dispatch.ip_spoofing_check = true
     config.action_dispatch.show_exceptions = true
-    config.action_dispatch.best_standards_support = true
     config.action_dispatch.tld_length = 1
     config.action_dispatch.ignore_accept_header = false
     config.action_dispatch.rescue_templates = { }

actionpack/test/dispatch/best_standards_support_test.rb

-require 'abstract_unit'
-
-class BestStandardsSupportTest < ActiveSupport::TestCase
-  def test_with_best_standards_support
-    _, headers, _ = app(true, {}).call({})
-    assert_equal "IE=Edge,chrome=1", headers["X-UA-Compatible"]
-  end
-
-  def test_with_builtin_best_standards_support
-    _, headers, _ = app(:builtin, {}).call({})
-    assert_equal "IE=Edge", headers["X-UA-Compatible"]
-  end
-
-  def test_without_best_standards_support
-    _, headers, _ = app(false, {}).call({})
-    assert_equal nil, headers["X-UA-Compatible"]
-  end
-
-  def test_appends_to_app_headers_without_duplication_after_multiple_requests
-    app_headers = { "X-UA-Compatible" => "requiresActiveX=true" }
-    _, headers, _ = app(true, app_headers).call({})
-    _, headers, _ = app(true, app_headers).call({})
-
-    expects = "requiresActiveX=true,IE=Edge,chrome=1"
-    assert_equal expects, headers["X-UA-Compatible"]
-  end
-
-  private
-
-    def app(type, headers)
-      app = proc { [200, headers, "response"] }
-      ActionDispatch::BestStandardsSupport.new(app, type)
-    end
-
-end

railties/lib/rails/application.rb

@@ -365,10 +365,6 @@ def default_middleware_stack #:nodoc:
         middleware.use ::Rack::Head
         middleware.use ::Rack::ConditionalGet
         middleware.use ::Rack::ETag, "no-cache"
-
-        if config.action_dispatch.best_standards_support
-          middleware.use ::ActionDispatch::BestStandardsSupport, config.action_dispatch.best_standards_support
-        end
       end
     end
 

railties/lib/rails/configuration.rb

@@ -27,11 +27,11 @@ module Configuration
     #
     # Middlewares can also be completely swapped out and replaced with others:
     #
-    #     config.middleware.swap ActionDispatch::BestStandardsSupport, Magical::Unicorns
+    #     config.middleware.swap ActionDispatch::Flash, Magical::Unicorns
     #
     # And finally they can also be removed from the stack completely:
     #
-    #     config.middleware.delete ActionDispatch::BestStandardsSupport
+    #     config.middleware.delete ActionDispatch::Flash
     #
     class MiddlewareStackProxy
       def initialize

railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

@@ -19,9 +19,6 @@
   # Print deprecation notices to the Rails logger.
   config.active_support.deprecation = :log
 
-  # Only use best-standards-support built into browsers.
-  config.action_dispatch.best_standards_support = :builtin
-
   <%- unless options.skip_active_record? -%>
   # Log the query plan for queries taking more than this (works
   # with SQLite, MySQL, and PostgreSQL).

railties/test/application/middleware/best_practices_test.rb

-require 'isolation/abstract_unit'
-
-module ApplicationTests
-  class BestPracticesTest < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
-
-    def setup
-      build_app
-      boot_rails
-      require 'rack/test'
-      extend Rack::Test::Methods
-      simple_controller
-    end
-
-    def teardown
-      teardown_app
-    end
-
-    test "simple controller in production mode returns best standards" do
-      get '/foo'
-      assert_equal "IE=Edge,chrome=1", last_response.headers["X-UA-Compatible"]
-    end
-
-    test "simple controller in development mode leaves out Chrome" do
-      app("development")
-      get "/foo"
-      assert_equal "IE=Edge", last_response.headers["X-UA-Compatible"]
-    end
-  end
-end

railties/test/application/middleware_test.rb

@@ -45,8 +45,7 @@ def app
         "ActionDispatch::ParamsParser",
         "Rack::Head",
         "Rack::ConditionalGet",
-        "Rack::ETag",
-        "ActionDispatch::BestStandardsSupport"
+        "Rack::ETag"
       ], middleware
     end