Bring abstract_controller up to date with rails/master

Resolved all the conflicts since 2.3.0 -> HEAD. Following is a list
of commits that could not be applied cleanly or are obviated with the
abstract_controller refactor. They all need to be revisited to ensure
that fixes made in 2.3 do not reappear in 3.0:

2259ecf368e6a6715966f69216e3ee86bf1a82a7
AR not available
  * This will be reimplemented with ActionORM or equivalent

06182ea02e92afad579998aa80144588e8865ac3
implicitly rendering a js response should not use the default layout
[#1844 state:resolved]
  * This will be handled generically

893e9eb99504705419ad6edac14d00e71cef5f12
Improve view rendering performance in development mode and reinstate
template recompiling in production [#1909 state:resolved]
  * We will need to reimplement rails-dev-boost on top of the refactor;
    the changes here are very implementation specific and cannot be
    cleanly applied. The following commits are implicated:

      199e750d46c04970b5e7684998d09405648ecbd4
      3942cb406e1d5db0ac00e03153809cc8dc4cc4db
      f8ea9f85d4f1e3e6f3b5d895bef6b013aa4b0690
      e3b166aab37ddc2fbab030b146eb61713b91bf55
      ae9f258e03c9fd5088da12c1c6cd216cc89a01f7
      44423126c6f6133a1d9cf1d0832b527e8711d40f

0cb020b4d6d838025859bd60fb8151c8e21b8e84
workaround for picking layouts based on wrong view_paths
[#1974 state:resolved]
  * The specifics of this commit no longer apply. Since it is a two-line
    commit, we will reimplement this change.

8c5cc66a831aadb159f3daaffa4208064c30af0e
make action_controller/layouts pick templates from the current instance's
view_paths instead of the class view_paths [#1974 state:resolved]
  * This does not apply at all. It should be trivial to apply the feature
    to the reimplemented ActionController::Base.

87e8b162463f13bd50d27398f020769460a770e3
fix HTML fallback for explicit templates [#2052 state:resolved]
  * There were a number of patches related to this that simply compounded
    each other. Basically none of them apply cleanly, and the underlying
    issue needs to be revisited. After discussing the underlying problem
    with Koz, we will defer these fixes for further discussion.

1 files changed, 309 insertions, 75 deletions

diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index a85751c657..a59829b23f 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -5,17 +5,24 @@ require 'action_view/helpers/form_tag_helper'
 
 module ActionView
   module Helpers
-    # Form helpers are designed to make working with models much easier compared to using just standard HTML
-    # elements by providing a set of methods for creating forms based on your models. This helper generates the HTML
-    # for forms, providing a method for each sort of input (e.g., text, password, select, and so on). When the form
-    # is submitted (i.e., when the user hits the submit button or <tt>form.submit</tt> is called via JavaScript), the form inputs will be bundled into the <tt>params</tt> object and passed back to the controller.
+    # Form helpers are designed to make working with models much easier
+    # compared to using just standard HTML elements by providing a set of
+    # methods for creating forms based on your models. This helper generates
+    # the HTML for forms, providing a method for each sort of input
+    # (e.g., text, password, select, and so on). When the form is submitted
+    # (i.e., when the user hits the submit button or <tt>form.submit</tt> is
+    # called via JavaScript), the form inputs will be bundled into the
+    # <tt>params</tt> object and passed back to the controller.
     #
-    # There are two types of form helpers: those that specifically work with model attributes and those that don't.
-    # This helper deals with those that work with model attributes; to see an example of form helpers that don't work
-    # with model attributes, check the ActionView::Helpers::FormTagHelper documentation.
+    # There are two types of form helpers: those that specifically work with
+    # model attributes and those that don't. This helper deals with those that
+    # work with model attributes; to see an example of form helpers that don't
+    # work with model attributes, check the ActionView::Helpers::FormTagHelper
+    # documentation.
     #
-    # The core method of this helper, form_for, gives you the ability to create a form for a model instance;
-    # for example, let's say that you have a model <tt>Person</tt> and want to create a new instance of it:
+    # The core method of this helper, form_for, gives you the ability to create
+    # a form for a model instance; for example, let's say that you have a model
+    # <tt>Person</tt> and want to create a new instance of it:
     #
     #     # Note: a @person variable will have been created in the controller.
     #     # For example: @person = Person.new
@@ -40,17 +47,22 @@ module ActionView
     #       <%= submit_tag 'Create' %>
     #     <% end %>
     #
-    # This example will render the <tt>people/_form</tt> partial, setting a local variable called <tt>form</tt> which references the yielded FormBuilder.
-    #
-    # The <tt>params</tt> object created when this form is submitted would look like:
+    # This example will render the <tt>people/_form</tt> partial, setting a
+    # local variable called <tt>form</tt> which references the yielded
+    # FormBuilder. The <tt>params</tt> object created when this form is
+    # submitted would look like:
     #
     #     {"action"=>"create", "controller"=>"persons", "person"=>{"first_name"=>"William", "last_name"=>"Smith"}}
     #
-    # The params hash has a nested <tt>person</tt> value, which can therefore be accessed with <tt>params[:person]</tt> in the controller.
-    # If were editing/updating an instance (e.g., <tt>Person.find(1)</tt> rather than <tt>Person.new</tt> in the controller), the objects
-    # attribute values are filled into the form (e.g., the <tt>person_first_name</tt> field would have that person's first name in it).
+    # The params hash has a nested <tt>person</tt> value, which can therefore
+    # be accessed with <tt>params[:person]</tt> in the controller. If were
+    # editing/updating an instance (e.g., <tt>Person.find(1)</tt> rather than
+    # <tt>Person.new</tt> in the controller), the objects attribute values are
+    # filled into the form (e.g., the <tt>person_first_name</tt> field would
+    # have that person's first name in it).
     #
-    # If the object name contains square brackets the id for the object will be inserted. For example:
+    # If the object name contains square brackets the id for the object will be
+    # inserted. For example:
     #
     #   <%= text_field "person[]", "name" %>
     #
@@ -58,8 +70,10 @@ module ActionView
     #
     #   <input type="text" id="person_<%= @person.id %>_name" name="person[<%= @person.id %>][name]" value="<%= @person.name %>" />
     #
-    # If the helper is being used to generate a repetitive sequence of similar form elements, for example in a partial
-    # used by <tt>render_collection_of_partials</tt>, the <tt>index</tt> option may come in handy. Example:
+    # If the helper is being used to generate a repetitive sequence of similar
+    # form elements, for example in a partial used by
+    # <tt>render_collection_of_partials</tt>, the <tt>index</tt> option may
+    # come in handy. Example:
     #
     #   <%= text_field "person", "name", "index" => 1 %>
     #
@@ -67,14 +81,17 @@ module ActionView
     #
     #   <input type="text" id="person_1_name" name="person[1][name]" value="<%= @person.name %>" />
     #
-    # An <tt>index</tt> option may also be passed to <tt>form_for</tt> and <tt>fields_for</tt>.  This automatically applies
-    # the <tt>index</tt> to all the nested fields.
+    # An <tt>index</tt> option may also be passed to <tt>form_for</tt> and
+    # <tt>fields_for</tt>.  This automatically applies the <tt>index</tt> to
+    # all the nested fields.
     #
-    # There are also methods for helping to build form tags in link:classes/ActionView/Helpers/FormOptionsHelper.html,
-    # link:classes/ActionView/Helpers/DateHelper.html, and link:classes/ActionView/Helpers/ActiveRecordHelper.html
+    # There are also methods for helping to build form tags in
+    # link:classes/ActionView/Helpers/FormOptionsHelper.html,
+    # link:classes/ActionView/Helpers/DateHelper.html, and
+    # link:classes/ActionView/Helpers/ActiveRecordHelper.html
     module FormHelper
-      # Creates a form and a scope around a specific model object that is used as
-      # a base for questioning about values for the fields.
+      # Creates a form and a scope around a specific model object that is used
+      # as a base for questioning about values for the fields.
       #
       # Rails provides succinct resource-oriented form generation with +form_for+
       # like this:
@@ -86,13 +103,15 @@ module ActionView
       #     <%= f.text_field :author %><br />
       #   <% end %>
       #
-      # There, +form_for+ is able to generate the rest of RESTful form parameters
-      # based on introspection on the record, but to understand what it does we
-      # need to dig first into the alternative generic usage it is based upon.
+      # There, +form_for+ is able to generate the rest of RESTful form
+      # parameters based on introspection on the record, but to understand what
+      # it does we need to dig first into the alternative generic usage it is
+      # based upon.
       #
       # === Generic form_for
       #
-      # The generic way to call +form_for+ yields a form builder around a model:
+      # The generic way to call +form_for+ yields a form builder around a
+      # model:
       #
       #   <% form_for :person, :url => { :action => "update" } do |f| %>
       #     <%= f.error_messages %>
@@ -103,8 +122,8 @@ module ActionView
       #   <% end %>
       #
       # There, the first argument is a symbol or string with the name of the
-      # object the form is about, and also the name of the instance variable the
-      # object is stored in.
+      # object the form is about, and also the name of the instance variable
+      # the object is stored in.
       #
       # The form builder acts as a regular form helper that somehow carries the
       # model. Thus, the idea is that
@@ -137,17 +156,18 @@ module ActionView
       # In any of its variants, the rightmost argument to +form_for+ is an
       # optional hash of options:
       #
-      # * <tt>:url</tt> - The URL the form is submitted to. It takes the same fields
-      #   you pass to +url_for+ or +link_to+. In particular you may pass here a
-      #   named route directly as well. Defaults to the current action.
+      # * <tt>:url</tt> - The URL the form is submitted to. It takes the same
+      #   fields you pass to +url_for+ or +link_to+. In particular you may pass
+      #   here a named route directly as well. Defaults to the current action.
       # * <tt>:html</tt> - Optional HTML attributes for the form tag.
       #
-      # Worth noting is that the +form_for+ tag is called in a ERb evaluation block,
-      # not an ERb output block. So that's <tt><% %></tt>, not <tt><%= %></tt>.
+      # Worth noting is that the +form_for+ tag is called in a ERb evaluation
+      # block, not an ERb output block. So that's <tt><% %></tt>, not
+      # <tt><%= %></tt>.
       #
       # Also note that +form_for+ doesn't create an exclusive scope. It's still
-      # possible to use both the stand-alone FormHelper methods and methods from
-      # FormTagHelper. For example:
+      # possible to use both the stand-alone FormHelper methods and methods
+      # from FormTagHelper. For example:
       #
       #   <% form_for :person, @person, :url => { :action => "update" } do |f| %>
       #     First name: <%= f.text_field :first_name %>
@@ -156,16 +176,16 @@ module ActionView
       #     Admin?    : <%= check_box_tag "person[admin]", @person.company.admin? %>
       #   <% end %>
       #
-      # This also works for the methods in FormOptionHelper and DateHelper that are
-      # designed to work with an object as base, like FormOptionHelper#collection_select
-      # and DateHelper#datetime_select.
+      # This also works for the methods in FormOptionHelper and DateHelper that
+      # are designed to work with an object as base, like
+      # FormOptionHelper#collection_select and DateHelper#datetime_select.
       #
       # === Resource-oriented style
       #
-      # As we said above, in addition to manually configuring the +form_for+ call,
-      # you can rely on automated resource identification, which will use the conventions
-      # and named routes of that approach. This is the preferred way to use +form_for+
-      # nowadays.
+      # As we said above, in addition to manually configuring the +form_for+
+      # call, you can rely on automated resource identification, which will use
+      # the conventions and named routes of that approach. This is the
+      # preferred way to use +form_for+ nowadays.
       #
       # For example, if <tt>@post</tt> is an existing record you want to edit
       #
@@ -205,8 +225,10 @@ module ActionView
       #
       # === Customized form builders
       #
-      # You can also build forms using a customized FormBuilder class. Subclass FormBuilder and override or define some more helpers,
-      # then use your custom builder. For example, let's say you made a helper to automatically add labels to form inputs.
+      # You can also build forms using a customized FormBuilder class. Subclass
+      # FormBuilder and override or define some more helpers, then use your
+      # custom builder. For example, let's say you made a helper to
+      # automatically add labels to form inputs.
       #
       #   <% form_for :person, @person, :url => { :action => "update" }, :builder => LabellingFormBuilder do |f| %>
       #     <%= f.text_field :first_name %>
@@ -219,16 +241,23 @@ module ActionView
       #
       #   <%= render :partial => f %>
       #
-      # The rendered template is <tt>people/_labelling_form</tt> and the local variable referencing the form builder is called <tt>labelling_form</tt>.
+      # The rendered template is <tt>people/_labelling_form</tt> and the local
+      # variable referencing the form builder is called
+      # <tt>labelling_form</tt>.
+      #
+      # The custom FormBuilder class is automatically merged with the options
+      # of a nested fields_for call, unless it's explicitely set.
       #
-      # In many cases you will want to wrap the above in another helper, so you could do something like the following:
+      # In many cases you will want to wrap the above in another helper, so you
+      # could do something like the following:
       #
       #   def labelled_form_for(record_or_name_or_array, *args, &proc)
       #     options = args.extract_options!
       #     form_for(record_or_name_or_array, *(args << options.merge(:builder => LabellingFormBuilder)), &proc)
       #   end
       #
-      # If you don't need to attach a form to a model instance, then check out FormTagHelper#form_tag.
+      # If you don't need to attach a form to a model instance, then check out
+      # FormTagHelper#form_tag.
       def form_for(record_or_name_or_array, *args, &proc)
         raise ArgumentError, "Missing block" unless block_given?
 
@@ -269,10 +298,12 @@ module ActionView
         options[:url] ||= polymorphic_path(object_or_array)
       end
 
-      # Creates a scope around a specific model object like form_for, but doesn't create the form tags themselves. This makes
-      # fields_for suitable for specifying additional model objects in the same form:
+      # Creates a scope around a specific model object like form_for, but
+      # doesn't create the form tags themselves. This makes fields_for suitable
+      # for specifying additional model objects in the same form.
+      #
+      # === Generic Examples
       #
-      # ==== Examples
       #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
       #     First name: <%= person_form.text_field :first_name %>
       #     Last name : <%= person_form.text_field :last_name %>
@@ -282,20 +313,166 @@ module ActionView
       #     <% end %>
       #   <% end %>
       #
-      # ...or if you have an object that needs to be represented as a different parameter, like a Client that acts as a Person:
+      # ...or if you have an object that needs to be represented as a different
+      # parameter, like a Client that acts as a Person:
       #
       #   <% fields_for :person, @client do |permission_fields| %>
       #     Admin?: <%= permission_fields.check_box :admin %>
       #   <% end %>
       #
-      # ...or if you don't have an object, just a name of the parameter
+      # ...or if you don't have an object, just a name of the parameter:
       #
       #   <% fields_for :person do |permission_fields| %>
       #     Admin?: <%= permission_fields.check_box :admin %>
       #   <% end %>
       #
-      # Note: This also works for the methods in FormOptionHelper and DateHelper that are designed to work with an object as base,
-      # like FormOptionHelper#collection_select and DateHelper#datetime_select.
+      # Note: This also works for the methods in FormOptionHelper and
+      # DateHelper that are designed to work with an object as base, like
+      # FormOptionHelper#collection_select and DateHelper#datetime_select.
+      #
+      # === Nested Attributes Examples
+      #
+      # When the object belonging to the current scope has a nested attribute
+      # writer for a certain attribute, fields_for will yield a new scope
+      # for that attribute. This allows you to create forms that set or change
+      # the attributes of a parent object and its associations in one go.
+      #
+      # Nested attribute writers are normal setter methods named after an
+      # association. The most common way of defining these writers is either
+      # with +accepts_nested_attributes_for+ in a model definition or by
+      # defining a method with the proper name. For example: the attribute
+      # writer for the association <tt>:address</tt> is called
+      # <tt>address_attributes=</tt>.
+      #
+      # Whether a one-to-one or one-to-many style form builder will be yielded
+      # depends on whether the normal reader method returns a _single_ object
+      # or an _array_ of objects.
+      #
+      # ==== One-to-one
+      #
+      # Consider a Person class which returns a _single_ Address from the
+      # <tt>address</tt> reader method and responds to the
+      # <tt>address_attributes=</tt> writer method:
+      #
+      #   class Person
+      #     def address
+      #       @address
+      #     end
+      #
+      #     def address_attributes=(attributes)
+      #       # Process the attributes hash
+      #     end
+      #   end
+      #
+      # This model can now be used with a nested fields_for, like so:
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% person_form.fields_for :address do |address_fields| %>
+      #       Street  : <%= address_fields.text_field :street %>
+      #       Zip code: <%= address_fields.text_field :zip_code %>
+      #     <% end %>
+      #   <% end %>
+      #
+      # When address is already an association on a Person you can use
+      # +accepts_nested_attributes_for+ to define the writer method for you:
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_one :address
+      #     accepts_nested_attributes_for :address
+      #   end
+      #
+      # If you want to destroy the associated model through the form, you have
+      # to enable it first using the <tt>:allow_destroy</tt> option for
+      # +accepts_nested_attributes_for+:
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_one :address
+      #     accepts_nested_attributes_for :address, :allow_destroy => true
+      #   end
+      #
+      # Now, when you use a form element with the <tt>_delete</tt> parameter,
+      # with a value that evaluates to +true+, you will destroy the associated
+      # model (eg. 1, '1', true, or 'true'):
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% person_form.fields_for :address do |address_fields| %>
+      #       ...
+      #       Delete: <%= address_fields.check_box :_delete %>
+      #     <% end %>
+      #   <% end %>
+      #
+      # ==== One-to-many
+      #
+      # Consider a Person class which returns an _array_ of Project instances
+      # from the <tt>projects</tt> reader method and responds to the
+      # <tt>projects_attributes=</tt> writer method:
+      #
+      #   class Person
+      #     def projects
+      #       [@project1, @project2]
+      #     end
+      #
+      #     def projects_attributes=(attributes)
+      #       # Process the attributes hash
+      #     end
+      #   end
+      #
+      # This model can now be used with a nested fields_for. The block given to
+      # the nested fields_for call will be repeated for each instance in the
+      # collection:
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% person_form.fields_for :projects do |project_fields| %>
+      #       <% if project_fields.object.active? %>
+      #         Name: <%= project_fields.text_field :name %>
+      #       <% end %>
+      #     <% end %>
+      #   <% end %>
+      #
+      # It's also possible to specify the instance to be used:
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% @person.projects.each do |project| %>
+      #       <% if project.active? %>
+      #         <% person_form.fields_for :projects, project do |project_fields| %>
+      #           Name: <%= project_fields.text_field :name %>
+      #         <% end %>
+      #       <% end %>
+      #     <% end %>
+      #   <% end %>
+      #
+      # When projects is already an association on Person you can use
+      # +accepts_nested_attributes_for+ to define the writer method for you:
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_many :projects
+      #     accepts_nested_attributes_for :projects
+      #   end
+      #
+      # If you want to destroy any of the associated models through the
+      # form, you have to enable it first using the <tt>:allow_destroy</tt>
+      # option for +accepts_nested_attributes_for+:
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_many :projects
+      #     accepts_nested_attributes_for :projects, :allow_destroy => true
+      #   end
+      #
+      # This will allow you to specify which models to destroy in the
+      # attributes hash by adding a form element for the <tt>_delete</tt>
+      # parameter with a value that evaluates to +true+
+      # (eg. 1, '1', true, or 'true'):
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% person_form.fields_for :projects do |project_fields| %>
+      #       Delete: <%= project_fields.check_box :_delete %>
+      #     <% end %>
+      #   <% end %>
       def fields_for(record_or_name_or_array, *args, &block)
         raise ArgumentError, "Missing block" unless block_given?
         options = args.extract_options!
@@ -451,7 +628,7 @@ module ActionView
       #
       # The HTML specification says unchecked check boxes are not successful, and
       # thus web browsers do not send them. Unfortunately this introduces a gotcha:
-      # if an Invoice model has a +paid+ flag, and in the form that edits a paid
+      # if an +Invoice+ model has a +paid+ flag, and in the form that edits a paid
       # invoice the user unchecks its check box, no +paid+ parameter is sent. So,
       # any mass-assignment idiom like
       #
@@ -459,12 +636,15 @@ module ActionView
       #
       # wouldn't update the flag.
       #
-      # To prevent this the helper generates a hidden field with the same name as
-      # the checkbox after the very check box. So, the client either sends only the
-      # hidden field (representing the check box is unchecked), or both fields.
-      # Since the HTML specification says key/value pairs have to be sent in the
-      # same order they appear in the form and Rails parameters extraction always
-      # gets the first occurrence of any given key, that works in ordinary forms.
+      # To prevent this the helper generates an auxiliary hidden field before
+      # the very check box. The hidden field has the same name and its
+      # attributes mimick an unchecked check box.
+      #
+      # This way, the client either sends only the hidden field (representing
+      # the check box is unchecked), or both fields. Since the HTML specification
+      # says key/value pairs have to be sent in the same order they appear in the
+      # form, and parameters extraction gets the last occurrence of any repeated
+      # key in the query string, that works for ordinary forms.
       #
       # Unfortunately that workaround does not work when the check box goes
       # within an array-like parameter, as in
@@ -475,22 +655,26 @@ module ActionView
       #   <% end %>
       #
       # because parameter name repetition is precisely what Rails seeks to distinguish
-      # the elements of the array.
+      # the elements of the array. For each item with a checked check box you
+      # get an extra ghost item with only that attribute, assigned to "0".
+      #
+      # In that case it is preferable to either use +check_box_tag+ or to use
+      # hashes instead of arrays.
       #
       # ==== Examples
       #   # Let's say that @post.validated? is 1:
       #   check_box("post", "validated")
-      #   # => <input type="checkbox" id="post_validated" name="post[validated]" value="1" />
-      #   #    <input name="post[validated]" type="hidden" value="0" />
+      #   # => <input name="post[validated]" type="hidden" value="0" />
+      #   #    <input type="checkbox" id="post_validated" name="post[validated]" value="1" />
       #
       #   # Let's say that @puppy.gooddog is "no":
       #   check_box("puppy", "gooddog", {}, "yes", "no")
-      #   # => <input type="checkbox" id="puppy_gooddog" name="puppy[gooddog]" value="yes" />
-      #   #    <input name="puppy[gooddog]" type="hidden" value="no" />
+      #   # => <input name="puppy[gooddog]" type="hidden" value="no" />
+      #   #    <input type="checkbox" id="puppy_gooddog" name="puppy[gooddog]" value="yes" />
       #
       #   check_box("eula", "accepted", { :class => 'eula_check' }, "yes", "no")
-      #   # => <input type="checkbox" class="eula_check" id="eula_accepted" name="eula[accepted]" value="yes" />
-      #   #    <input name="eula[accepted]" type="hidden" value="no" />
+      #   # => <input name="eula[accepted]" type="hidden" value="no" />
+      #   #    <input type="checkbox" class="eula_check" id="eula_accepted" name="eula[accepted]" value="yes" />
       #
       def check_box(object_name, method, options = {}, checked_value = "1", unchecked_value = "0")
         InstanceTag.new(object_name, method, self, options.delete(:object)).to_check_box_tag(options, checked_value, unchecked_value)
@@ -498,8 +682,10 @@ module ActionView
 
       # Returns a radio button tag for accessing a specified attribute (identified by +method+) on an object
       # assigned to the template (identified by +object+). If the current value of +method+ is +tag_value+ the
-      # radio button will be checked. Additional options on the input tag can be passed as a
-      # hash with +options+.
+      # radio button will be checked.
+      #
+      # To force the radio button to be checked pass <tt>:checked => true</tt> in the
+      # +options+ hash. You may pass HTML options there as well.
       #
       # ==== Examples
       #   # Let's say that @post.category returns "rails":
@@ -605,7 +791,9 @@ module ActionView
         end
         options["checked"] = "checked" if checked
         add_default_name_and_id(options)
-        tag("input", options) << tag("input", "name" => options["name"], "type" => "hidden", "value" => options['disabled'] && checked ? checked_value : unchecked_value)
+        hidden = tag("input", "name" => options["name"], "type" => "hidden", "value" => options['disabled'] && checked ? checked_value : unchecked_value)
+        checkbox = tag("input", options)
+        hidden + checkbox
       end
 
       def to_boolean_select_tag(options = {})
@@ -758,9 +946,18 @@ module ActionView
           index = ""
         end
 
+        if options[:builder]
+          args << {} unless args.last.is_a?(Hash)
+          args.last[:builder] ||= options[:builder]
+        end
+
         case record_or_name_or_array
         when String, Symbol
-          name = "#{object_name}#{index}[#{record_or_name_or_array}]"
+          if nested_attributes_association?(record_or_name_or_array)
+            return fields_for_with_nested_attributes(record_or_name_or_array, args, block)
+          else
+            name = "#{object_name}#{index}[#{record_or_name_or_array}]"
+          end
         when Array
           object = record_or_name_or_array.last
           name = "#{object_name}#{index}[#{ActionController::RecordIdentifier.singular_class_name(object)}]"
@@ -802,6 +999,43 @@ module ActionView
         def objectify_options(options)
           @default_options.merge(options.merge(:object => @object))
         end
+
+        def nested_attributes_association?(association_name)
+          @object.respond_to?("#{association_name}_attributes=")
+        end
+
+        def fields_for_with_nested_attributes(association_name, args, block)
+          name = "#{object_name}[#{association_name}_attributes]"
+          association = @object.send(association_name)
+          explicit_object = args.first if args.first.respond_to?(:new_record?)
+
+          if association.is_a?(Array)
+            children = explicit_object ? [explicit_object] : association
+            explicit_child_index = args.last[:child_index] if args.last.is_a?(Hash)
+
+            children.map do |child|
+              fields_for_nested_model("#{name}[#{explicit_child_index || nested_child_index}]", child, args, block)
+            end.join
+          else
+            fields_for_nested_model(name, explicit_object || association, args, block)
+          end
+        end
+
+        def fields_for_nested_model(name, object, args, block)
+          if object.new_record?
+            @template.fields_for(name, object, *args, &block)
+          else
+            @template.fields_for(name, object, *args) do |builder|
+              @template.concat builder.hidden_field(:id)
+              block.call(builder)
+            end
+          end
+        end
+
+        def nested_child_index
+          @nested_child_index ||= -1
+          @nested_child_index += 1
+        end
     end
   end
 
@@ -809,4 +1043,4 @@ module ActionView
     cattr_accessor :default_form_builder
     self.default_form_builder = ::ActionView::Helpers::FormBuilder
   end
-end
+end
\ No newline at end of file