7 files changed, 20 insertions, 412 deletions
diff --git a/railties/guides/source/active_resource_basics.textile b/railties/guides/source/active_resource_basics.textile
deleted file mode 100644
index 37abb8a640..0000000000
--- a/railties/guides/source/active_resource_basics.textile
+++ /dev/null
@@ -1,120 +0,0 @@
-h2. Active Resource Basics
-
-This guide should provide you with all you need to get started managing the connection between business objects and RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics.
-
-endprologue.
-
-WARNING. This Guide is based on Rails 3.0. Some of the code shown here will not work in earlier versions of Rails.
-
-h3. Introduction
-
-Active Resource allows you to connect with RESTful web services. So, in Rails, Resource classes inherited from +ActiveResource::Base+ and live in  +app/models+.
-
-h3. Configuration and Usage
-
-Putting Active Resource to use is very similar to Active Record.  It's as simple as creating a model class
-that inherits from ActiveResource::Base and providing a <tt>site</tt> class variable to it:
-
-<ruby>
-class Person < ActiveResource::Base
-  self.site = "http://api.people.com:3000/"
-end
-</ruby>
-
-Now the Person class is REST enabled and can invoke REST services very similarly to how Active Record invokes
-life cycle methods that operate against a persistent store.
-
-h3. Reading and Writing Data
-
-Active Resource make request over HTTP using a standard JSON format. It mirrors the RESTful routing built into Action Controller but will also work with any other REST service that properly implements the protocol.
-
-h4. Read
-
-Read requests use the GET method and expect the JSON form of whatever resource/resources is/are being requested.
-
-<ruby>
-# Find a person with id = 1
-person = Person.find(1)
-# Check if a person exists with id = 1
-Person.exists?(1)  # => true
-# Get all resources of Person class
-Person.all
-</ruby>
-
-h4. Create
-
-Creating a new resource submits the JSON form of the resource as the body of the request with HTTP POST method and parse the response into Active Resource object.
-
-<ruby>
-person = Person.create(:name => 'Vishnu')
-person.id  # => 1
-</ruby>
-
-h4. Update
-
-To update an existing resource, 'save' method is used. This method make a HTTP PUT request in JSON format.
-
-<ruby>
-person = Person.find(1)
-person.name = 'Atrai'
-person.save
-</ruby>
-
-h4. Delete
-
-'destroy' method makes a HTTP DELETE request for an existing resource in JSON format to delete that resource.
-
-<ruby>
-person = Person.find(1)
-person.destroy
-</ruby>
-
-h3. Validations
-
-Module to support validation and errors with Active Resource objects. The module overrides Base#save to rescue ActiveResource::ResourceInvalid exceptions and parse the errors returned in the web service response. The module also adds an errors collection that mimics the interface of the errors provided by ActiveModel::Errors.
-
-h4. Validating client side resources by overriding validation methods in base class
-
-<ruby>
-class Person < ActiveResource::Base
-   self.site = "http://api.people.com:3000/"
-
-   protected
-
-   def validate
-     errors.add("last", "has invalid characters") unless last =~ /[a-zA-Z]*/
-   end
-end
-</ruby>
-
-h4. Validating client side resources
-
-Consider a Person resource on the server requiring both a first_name and a last_name with a validates_presence_of :first_name, :last_name declaration in the model:
-
-<ruby>
-person = Person.new(:first_name => "Jim", :last_name => "")
-person.save                   # => false (server returns an HTTP 422 status code and errors)
-person.valid?                 # => false
-person.errors.empty?          # => false
-person.errors.count           # => 1
-person.errors.full_messages   # => ["Last name can't be empty"]
-person.errors[:last_name]  # => ["can't be empty"]
-person.last_name = "Halpert"
-person.save                   # => true (and person is now saved to the remote service)
-</ruby>
-
-h4. Public instance methods
-
-ActiveResource::Validations have three public instance methods
-
-h5. errors()
-
-This will return errors object that holds all information about attribute error messages
-
-h5. save_with_validation(options=nil)
-
-This validates the resource with any local validations written in base class and then it will try to POST if there are no errors.
-
-h5. valid?
-
-Runs all the local validations and will return true if no errors.
diff --git a/railties/guides/source/api_app.textile b/railties/guides/source/api_app.textile
deleted file mode 100644
index 9bbf7b36b1..0000000000
--- a/railties/guides/source/api_app.textile
+++ /dev/null
@@ -1,275 +0,0 @@
-h2. Using Rails for API-only Apps
-
-In this guide you will learn:
-
-* What Rails provides for API-only applications
-* How to configure Rails to start without any browser features
-* How to decide which middlewares you will want to include
-* How to decide which modules to use in your controller
-
-NOTE: This guide reflects features that have not yet been fully implemented. Docs first :)
-
-endprologue.
-
-h3. What is an API app?
-
-Traditionally, when people said that they used Rails as an "API", they meant providing a programmatically accessible API alongside their web application.
-For example, GitHub provides "an API":http://developer.github.com that you can use from your own custom clients.
-
-With the advent of client-side frameworks, more developers are using Rails to build a backend that is shared between their web application and other native applications.
-
-For example, Twitter uses its "public API":https://dev.twitter.com in its web application, which is built as a static site that consumes JSON resources.
-
-Instead of using Rails to generate dynamic HTML that will communicate with the server through forms and links, many developers are treating their web application as just another client, delivered as static HTML, CSS and JavaScript, and consuming a simple JSON API
-
-This guide covers building a Rails application that serves JSON resources to an API client *or* client-side framework.
-
-h3. Why use Rails for JSON APIs?
-
-The first question a lot of people have when thinking about building a JSON API using Rails is: "isn't using Rails to spit out some JSON overkill? Shouldn't I just use something like Sinatra?"
-
-For very simple APIs, this may be true. However, even in very HTML-heavy applications, most of an application's logic is actually outside of the view layer.
-
-The reason most people use Rails is that it provides a set of defaults that allows us to get up and running quickly without having to make a lot of trivial decisions.
-
-Let's take a look at some of the things that Rails provides out of the box that are still applicable to API applications.
-
-Handled at the middleware layer:
-
-* Reloading: Rails applications support transparent reloading. This works even if your application gets big and restarting the server for every request becomes non-viable.
-* Development Mode: Rails application come with smart defaults for development, making development pleasant without compromising production-time performance.
-* Test Mode: Ditto test mode.
-* Logging: Rails applications log every request, with a level of verbosity appropriate for the current mode. Rails logs in development include information about the request environment, database queries, and basic performance information.
-* Security: Rails detects and thwarts "IP spoofing attacks":http://en.wikipedia.org/wiki/IP_address_spoofing and handles cryptographic signatures in a "timing attack":http://en.wikipedia.org/wiki/Timing_attack aware way. Don't know what an IP spoofing attack or a timing attack is? Exactly.
-* Parameter Parsing: Want to specify your parameters as JSON instead of as a URL-encoded String? No problem. Rails will decode the JSON for you and make it available in +params+. Want to use nested URL-encoded params? That works too.
-* Conditional GETs: Rails handles conditional +GET+, (+ETag+ and +Last-Modified+), processing request headers and returning the correct response headers and status code. All you need to do is use the "stale?":http://api.rubyonrails.org/classes/ActionController/ConditionalGet.html#method-i-stale-3F check in your controller, and Rails will handle all of the HTTP details for you.
-* Caching: If you use +dirty?+ with public cache control, Rails will automatically cache your responses. You can easily configure the cache store.
-* HEAD requests: Rails will transparently convert +HEAD+ requests into +GET+ requests, and return just the headers on the way out. This makes +HEAD+ work reliably in all Rails APIs.
-
-While you could obviously build these up in terms of existing Rack middlewares, I think this list demonstrates that the default Rails middleware stack provides a lot of value, even if you're "just generating JSON".
-
-Handled at the ActionPack layer:
-
-* Resourceful Routing: If you're building a RESTful JSON API, you want to be using the Rails router. Clean and conventional mapping from HTTP to controllers means not having to spend time thinking about how to model your API in terms of HTTP.
-* URL Generation: The flip side of routing is URL generation. A good API based on HTTP includes URLs (see "the GitHub gist API":http://developer.github.com/v3/gists/ for an example).
-* Header and Redirection Responses: +head :no_content+ and +redirect_to user_url(current_user)+ come in handy. Sure, you could manually add the response headers, but why?
-* Content Negotiation: The Rails +respond_to+ and +respond_with+ features automatically figure out which MIME type to serve, based on the request's +Accept+ header and available types. If you ever need to add support for types other than JSON (XML, CSV, or some proprietary format), this will come in handy.
-* Caching: Rails provides page, action and fragment caching. Fragment caching is especially helpful when building up a nested JSON object.
-* Basic, Digest and Token Authentication: Rails comes with out-of-the-box support for three kinds of HTTP authentication.
-* Instrumentation: Rails 3.0 added an instrumentation API that will trigger registered handlers for a variety of events, such as action processing, sending a file or data, redirection, and database queries. The payload of each event comes with relevant information (for the action processing event, the payload includes the controller, action, params, request format, request method and the request's full path).
-* Generators: This may be passé for advanced Rails users, but it can be nice to generate a resource and get your model, controller, test stubs, and routes created for you in a single command.
-* Plugins: Many third-party libraries come with support for Rails that reduces or eliminates the cost of setting up and gluing together the library and the web framework. This includes things like overriding default generators, adding rake tasks, and honoring Rails choices (like the logger and cache backend).
-
-Of course, the Rails boot process also glues together all registered components. For example, the Rails boot process is what uses your +config/database.yml+ file when configuring ActiveRecord.
-
-**The short version is**: you may not have thought about which parts of Rails are still applicable even if you remove the view layer, but the answer turns out to be "most of it".
-
-h3. The Basic Configuration
-
-If you're building a Rails application that will be an API server first and foremost, you can start with a more limited subset of Rails and add in features as needed.
-
-You can generate a new bare Rails app:
-
-<shell>
-$ rails new my_api --http
-</shell>
-
-This will do three main things for you:
-
-* Configure your application to start with a more limited set of middleware than normal. Specifically, it will not include any middleware primarily useful for browser applications (like cookie support) by default.
-* Make +ApplicationController+ inherit from +ActionController::HTTP+ instead of +ActionController::Base+. As with middleware, this will leave out any +ActionController+ modules that provide functionality primarily used by browser applications.
-* Configure the generators to skip generating views, helpers and assets when you generate a new resource.
-
-If you want to take an existing app and make it an API app, follow the following steps.
-
-In +config/application.rb+ add the following lines at the top of the +Application+ class:
-
-<ruby>
-config.middleware.http_only!
-config.generators.http_only!
-</ruby>
-
-Change +app/controllers/application_controller.rb+:
-
-<ruby>
-# instead of
-class ApplicationController < ActionController::Base
-end
-
-# do
-class ApplicationController < ActionController::HTTP
-end
-</ruby>
-
-h3. Choosing Middlewares
-
-An API application comes with the following middlewares by default.
-
-* +Rack::Cache+: Caches responses with public +Cache-Control+ headers using HTTP caching semantics. See below for more information.
-* +Rack::Sendfile+: Uses a front-end server's file serving support from your Rails application.
-* +Rack::Lock+: If your application is not marked as threadsafe (+config.threadsafe!+), this middleware will add a mutex around your requests.
-* +ActionDispatch::RequestId+:
-* +Rails::Rack::Logger+:
-* +ActionDispatch::ShowExceptions+: Rescue exceptions and re-dispatch them to an exception handling application
-* +ActionDispatch::DebugExceptions+: Log exceptions
-* +ActionDispatch::RemoteIp+: Protect against IP spoofing attacks
-* +ActionDispatch::Reloader+: In development mode, support code reloading.
-* +ActionDispatch::ParamsParser+: Parse XML, YAML and JSON parameters when the request's +Content-Type+ is one of those.
-* +ActionDispatch::Head+: Dispatch +HEAD+ requests as +GET+ requests, and return only the status code and headers.
-* +Rack::ConditionalGet+: Supports the +stale?+ feature in Rails controllers.
-* +Rack::ETag+: Automatically set an +ETag+ on all string responses. This means that if the same response is returned from a controller for the same URL, the server will return a +304 Not Modified+, even if no additional caching steps are taken. This is primarily a client-side optimization; it reduces bandwidth costs but not server processing time.
-
-Other plugins, including +ActiveRecord+, may add additional middlewares. In general, these middlewares are agnostic to the type of app you are building, and make sense in an API-only Rails application.
-
-You can get a list of all middlewares in your application via:
-
-<shell>
-$ rake middleware
-</shell>
-
-h4. Using Rack::Cache
-
-When used with Rails, +Rack::Cache+ uses the Rails cache store for its entity and meta stores. This means that if you use memcache, for your Rails app, for instance, the built-in HTTP cache will use memcache.
-
-To make use of +Rack::Cache+, you will want to use +stale?+ in your controller. Here's an example of +stale?+ in use.
-
-<ruby>
-def show
-  @post = Post.find(params[:id])
-
-  if stale?(:last_modified => @post.updated_at)
-    render json: @post
-  end
-end
-</ruby>
-
-The call to +stale?+ will compare the +If-Modified-Since+ header in the request with +@post.updated_at+. If the header is newer than the last modified, this action will return a +304 Not Modified+ response. Otherwise, it will render the response and include a +Last-Modified+ header with the response.
-
-Normally, this mechanism is used on a per-client basis. +Rack::Cache+ allows us to share this caching mechanism across clients. We can enable cross-client caching in the call to +stale?+
-
-<ruby>
-def show
-  @post = Post.find(params[:id])
-
-  if stale?(:last_modified => @post.updated_at, :public => true)
-    render json: @post
-  end
-end
-</ruby>
-
-This means that +Rack::Cache+ will store off +Last-Modified+ value for a URL in the Rails cache, and add an +If-Modified-Since+ header to any subsequent inbound requests for the same URL.
-
-Think of it as page caching using HTTP semantics.
-
-NOTE: The +Rack::Cache+ middleware is always outside of the +Rack::Lock+ mutex, even in single-threaded apps.
-
-h4. Using Rack::Sendfile
-
-When you use the +send_file+ method in a Rails controller, it sets the +X-Sendfile+ header. +Rack::Sendfile+ is responsible for actually sending the file.
-
-If your front-end server supports accelerated file sending, +Rack::Sendfile+ will offload the actual file sending work to the front-end server.
-
-You can configure the name of the header that your front-end server uses for this purposes using +config.action_dispatch.x_sendfile_header+ in the appropriate environment config file.
-
-You can learn more about how to use +Rack::Sendfile+ with popular front-ends in "the Rack::Sendfile documentation":http://rubydoc.info/github/rack/rack/master/Rack/Sendfile
-
-The values for popular servers once they are configured to support accelerated file sending:
-
-<ruby>
-# Apache and lighttpd
-config.action_dispatch.x_sendfile_header = "X-Sendfile"
-
-# nginx
-config.action_dispatch.x_sendfile_header = "X-Accel-Redirect"
-</ruby>
-
-Make sure to configure your server to support these options following the instructions in the +Rack::Sendfile+ documentation.
-
-NOTE: The +Rack::Sendfile+ middleware is always outside of the +Rack::Lock+ mutex, even in single-threaded apps.
-
-h4. Using ActionDispatch::ParamsParser
-
-+ActionDispatch::ParamsParser+ will take parameters from the client in JSON and make them available in your controller as +params+.
-
-To use this, your client will need to make a request with JSON-encoded parameters and specify the +Content-Type+ as +application/json+.
-
-Here's an example in jQuery:
-
-<plain>
-jQuery.ajax({
-  type: 'POST',
-  url: '/people'
-  dataType: 'json',
-  contentType: 'application/json',
-  data: JSON.stringify({ person: { firstName: "Yehuda", lastName: "Katz" } }),
-
-  success: function(json) { }
-});
-</plain>
-
-+ActionDispatch::ParamsParser+ will see the +Content-Type+ and your params will be +{ :person => { :firstName => "Yehuda", :lastName => "Katz" } }+.
-
-h4. Other Middlewares
-
-Rails ships with a number of other middlewares that you might want to use in an API app, especially if one of your API clients is the browser:
-
-* +Rack::SSL+: Redirects any HTTP request to HTTPS.
-* +Rack::Runtime+: Adds a header to the response listing the total runtime of the request.
-* +Rack::MethodOverride+: Allows the use of the +_method+ hack to route POST requests to other verbs.
-* +ActionDispatch::Cookies+: Supports the +cookie+ method in +ActionController+, including support for signed and encrypted cookies.
-* +ActionDispatch::Flash+: Supports the +flash+ mechanism in +ActionController+.
-* +ActionDispatch::BestStandards+: Tells Internet Explorer to use the most standards-compliant available renderer. In production mode, if ChromeFrame is available, use ChromeFrame.
-* Session Management: If a +config.session_store+ is supplied, this middleware makes the session available as the +session+ method in +ActionController+.
-
-Any of these middlewares can be adding via:
-
-<ruby>
-config.middleware.use Rack::MethodOverride
-</ruby>
-
-h4. Removing Middlewares
-
-If you don't want to use a middleware that is included by default in the API-only middleware set, you can remove it using +config.middleware.delete+:
-
-<ruby>
-config.middleware.delete ::Rack::Sendfile
-</ruby>
-
-Keep in mind that removing these features may remove support for certain features in +ActionController+.
-
-h3. Choosing Controller Modules
-
-An API application (using +ActionController::HTTP+) comes with the following controller modules by default:
-
-* +AbstractController::Translation+: Support for the +l+ and +t+ localization and translation methods. These delegate to +I18n.translate+ and +I18n.localize+.
-* +ActionController::UrlFor+: Makes +url_for+ and friends available.
-* +ActionController::Redirecting+: Support for +redirect_to+
-* +ActionController::Renderers::JSON+: Support for +render :json+
-* +ActionController::ConditionalGet+: Support for +stale?+
-* +ActionController::RackDelegation+: Support for the +request+ and +response+ methods returning +ActionDispatch::Request+ and +ActionDispatch::Response+ objects.
-* +ActionController::MimeResponds+: Support for content negotiation (+respond_to+, +respond_with+)
-* +ActionController::DataStreaming+: Support for +send_file+ and +send_data+
-* +AbstractController::Callbacks+: Support for +before_filter+ and friends
-* +ActionController::Instrumentation+: Support for the instrumentation hooks defined by +ActionController+ (see "the source":https://github.com/rails/rails/blob/master/actionpack/lib/action_controller/metal/instrumentation.rb for more).
-
-Other plugins may add additional modules. You can get a list of all modules included into +ActionController::HTTP+ in the rails console:
-
-<shell>
-$ irb
->> ActionController::HTTP.ancestors - ActionController::Metal.ancestors
-</shell>
-
-h4. Adding Other Modules
-
-All ActionController modules know about their dependent modules, so you can feel free to include any modules into your controllers, and all dependencies will be included and set up as well.
-
-Some common modules you might want to add:
-
-* +ActionController::HTTPAuthentication::Basic+ (or +Digest+ or +Token): Support for basic, digest or token HTTP authentication.
-* +ActionController::Rendering+: Support for templating and +ActionView+.
-* +AbstractController::Layouts+: Support for layouts when rendering.
-* +ActionController::Renderers::XML+: Support for +render :xml+.
-* +ActionController::Cookies+: Support for +cookies+, which includes support for signed and encrypted cookies. This requires the cookie middleware.
-* +ActionController::Rescue+: Support for +rescue_from+.
-
-The best place to add a module is in your +ApplicationController+. You can also add modules to individual controllers.
diff --git a/railties/guides/source/command_line.textile b/railties/guides/source/command_line.textile
index fe4a84dae9..463c2b172b 100644
--- a/railties/guides/source/command_line.textile
+++ b/railties/guides/source/command_line.textile
@@ -374,7 +374,6 @@ Rails version             4.0.0.beta
 JavaScript Runtime        Node.js (V8)
 Active Record version     4.0.0.beta
 Action Pack version       4.0.0.beta
-Active Resource version   4.0.0.beta
 Action Mailer version     4.0.0.beta
 Active Support version    4.0.0.beta
 Middleware                ActionDispatch::Static, Rack::Lock, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, Rails::Rack::Logger, ActionDispatch::ShowExceptions, ActionDispatch::DebugExceptions, ActionDispatch::RemoteIp, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, ActionDispatch::ParamsParser, ActionDispatch::Head, Rack::ConditionalGet, Rack::ETag, ActionDispatch::BestStandardsSupport
diff --git a/railties/guides/source/configuring.textile b/railties/guides/source/configuring.textile
index 28d198c00b..cfad642e0d 100644
--- a/railties/guides/source/configuring.textile
+++ b/railties/guides/source/configuring.textile
@@ -288,8 +288,6 @@ h4. Configuring Active Record
 
 * +config.active_record.whitelist_attributes+ will create an empty whitelist of attributes available for mass-assignment security for all models in your app.
 
-* +config.active_record.identity_map+ controls whether the identity map is enabled, and is false by default.
-
 * +config.active_record.auto_explain_threshold_in_seconds+ configures the threshold for automatic EXPLAINs (+nil+ disables this feature). Queries exceeding the threshold get their query plan logged. Default is 0.5 in development mode.
 
 * +config.active_record.dependent_restrict_raises+ will control the behavior when an object with a <tt>:dependent => :restrict</tt> association is deleted. Setting this to false will prevent +DeleteRestrictionError+ from being raised and instead will add an error on the model object. Defaults to false in the development mode.
@@ -439,12 +437,6 @@ config.action_mailer.observers = ["MailObserver"]
 config.action_mailer.interceptors = ["MailInterceptor"]
 </ruby>
 
-h4. Configuring Active Resource
-
-There is a single configuration setting available on +config.active_resource+:
-
-* +config.active_resource.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Resource. Set to +nil+ to disable logging.
-
 h4. Configuring Active Support
 
 There are a few configuration options available in Active Support:
@@ -713,8 +705,6 @@ The error occurred while evaluating nil.each
 
 *+action_mailer.compile_config_methods+* Initializes methods for the config settings specified so that they are quicker to access.
 
-*+active_resource.set_configs+* Sets up Active Resource by using the settings in +config.active_resource+ by +send+'ing the method names as setters to +ActiveResource::Base+ and passing the values through.
-
 *+set_load_path+* This initializer runs before +bootstrap_hook+. Adds the +vendor+, +lib+, all directories of +app+ and any paths specified by +config.load_paths+ to +$LOAD_PATH+.
 
 *+set_autoload_paths+* This initializer runs before +bootstrap_hook+. Adds all sub-directories of +app+ and paths specified by +config.autoload_paths+ to +ActiveSupport::Dependencies.autoload_paths+.
diff --git a/railties/guides/source/engines.textile b/railties/guides/source/engines.textile
index 5f7eb5290c..6ae9504c23 100644
--- a/railties/guides/source/engines.textile
+++ b/railties/guides/source/engines.textile
@@ -315,7 +315,7 @@ resources :posts do
 end
 </ruby>
 
-This creates a nested route for the comments, which is what the form requires. 
+This creates a nested route for the comments, which is what the form requires.
 
 The route now exists, but the controller that this route goes to does not. To create it, run this command:
 
@@ -361,7 +361,7 @@ This is the final part required to get the new comment form working. Displaying
     * "/Users/ryan/Sites/side_projects/blorgh/app/views"
 </text>
 
-The engine is unable to find the partial required for rendering the comments. Rails has looked firstly in the application's (+test/dummy+) +app/views+ directory and then in the engine's +app/views+ directory. When it can't find it, it will throw this error. The engine knows to look for +blorgh/comments/comment+ because the model object it is receiving is from the +Blorgh::Comment+ class. 
+The engine is unable to find the partial required for rendering the comments. Rails has looked firstly in the application's (+test/dummy+) +app/views+ directory and then in the engine's +app/views+ directory. When it can't find it, it will throw this error. The engine knows to look for +blorgh/comments/comment+ because the model object it is receiving is from the +Blorgh::Comment+ class.
 
 This partial will be responsible for rendering just the comment text, for now. Create a new file at +app/views/blorgh/comments/_comment.html.erb+ and put this line inside it:
 
@@ -440,6 +440,18 @@ The first timestamp (+\[timestamp_1\]+) will be the current time and the second
 
 To run these migrations within the context of the application, simply run +rake db:migrate+. When accessing the engine through +http://localhost:3000/blog+, the posts will be empty. This is because the table created inside the application is different from the one created within the engine. Go ahead, play around with the newly mounted engine. You'll find that it's the same as when it was only an engine.
 
+If you would like to run migrations only from one engine, you can do it by specifying +SCOPE+:
+
+<shell>
+rake db:migrate SCOPE=blorgh
+</shell>
+
+This may be useful if you want to revert engine's migrations before removing it. In order to revert all migrations from blorgh engine you can run such code:
+
+<shell>
+rake db:migrate SCOPE=blorgh VERSION=0
+</shell>
+
 h4. Using a class provided by the application
 
 When an engine is created, it may want to use specific classes from an application to provide links between the pieces of the engine and the pieces of the application. In the case of the +blorgh+ engine, making posts and comments have authors would make a lot of sense.
@@ -481,12 +493,12 @@ private
   end
 </ruby>
 
-By defining that the +author+ association's object is represented by the +User+ class a link is established between the engine and the application. There needs to be a way of associating the records in the +blorgh_posts+ table with the records in the +users+ table. Because the association is called +author+, there should be an +author_id+ column added to the +blorgh_posts+ table. 
+By defining that the +author+ association's object is represented by the +User+ class a link is established between the engine and the application. There needs to be a way of associating the records in the +blorgh_posts+ table with the records in the +users+ table. Because the association is called +author+, there should be an +author_id+ column added to the +blorgh_posts+ table.
 
 To generate this new column, run this command within the engine:
 
 <shell>
-$ rails g migration add_author_id_to_blorgh_posts author_id:integer 
+$ rails g migration add_author_id_to_blorgh_posts author_id:integer
 </shell>
 
 NOTE: Due to the migration's name and the column specification after it, Rails will automatically know that you want to add a column to a specific table and write that into the migration for you. You don't need to tell it any more than this.
diff --git a/railties/guides/source/initialization.textile b/railties/guides/source/initialization.textile
index 5ae9cf0f2b..69e5c1edcc 100644
--- a/railties/guides/source/initialization.textile
+++ b/railties/guides/source/initialization.textile
@@ -159,7 +159,6 @@ In a standard Rails application, there's a +Gemfile+ which declares all dependen
 * actionpack (3.1.0.beta)
 * activemodel (3.1.0.beta)
 * activerecord (3.1.0.beta)
-* activeresource (3.1.0.beta)
 * activesupport (3.1.0.beta)
 * arel (2.0.7)
 * builder (3.0.0)
@@ -491,7 +490,6 @@ require "rails"
     active_record
     action_controller
     action_mailer
-    active_resource
     rails/test_unit
 ).each do |framework|
   begin
diff --git a/railties/guides/source/upgrading_ruby_on_rails.textile b/railties/guides/source/upgrading_ruby_on_rails.textile
index 731d56c850..e63548abc9 100644
--- a/railties/guides/source/upgrading_ruby_on_rails.textile
+++ b/railties/guides/source/upgrading_ruby_on_rails.textile
@@ -34,6 +34,10 @@ h4(#plugins4_0). vendor/plugins
 
 Rails 4.0 no longer supports loading plugins from <tt>vendor/plugins</tt>. You must replace any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, <tt>lib/my_plugin/*</tt> and add an appropriate initializer in <tt>config/initializers/my_plugin.rb</tt>.
 
+h4(#identity_map4_0). IdentityMap
+
+Rails 4.0 has removed <tt>IdentityMap</tt> from <tt>ActiveRecord</tt>, due to "some inconsistencies with associations":https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6. If you have manually enabled it in your application, you will have to remove the following config that has no effect anymore: <tt>config.active_record.identity_map</tt>.
+
 h3. Upgrading from Rails 3.1 to Rails 3.2
 
 If your application is currently on any version of Rails older than 3.1.x, you should upgrade to Rails 3.1 before attempting an update to Rails 3.2.