Move actionpack/lib/action_view* into actionview/lib

5 files changed, 788 insertions, 0 deletions

diff --git a/actionview/lib/action_view/renderer/abstract_renderer.rb b/actionview/lib/action_view/renderer/abstract_renderer.rb
new file mode 100644
index 0000000000..73c19a0ae2
--- /dev/null
+++ b/actionview/lib/action_view/renderer/abstract_renderer.rb
@@ -0,0 +1,47 @@
+module ActionView
+  # This class defines the interface for a renderer. Each class that
+  # subclasses +AbstractRenderer+ is used by the base +Renderer+ class to
+  # render a specific type of object.
+  #
+  # The base +Renderer+ class uses its +render+ method to delegate to the
+  # renderers. These currently consist of
+  #
+  #   PartialRenderer - Used for rendering partials
+  #   TemplateRenderer - Used for rendering other types of templates
+  #   StreamingTemplateRenderer - Used for streaming
+  #
+  # Whenever the +render+ method is called on the base +Renderer+ class, a new
+  # renderer object of the correct type is created, and the +render+ method on
+  # that new object is called in turn. This abstracts the setup and rendering
+  # into a separate classes for partials and templates.
+  class AbstractRenderer #:nodoc:
+    delegate :find_template, :template_exists?, :with_fallbacks, :with_layout_format, :formats, :to => :@lookup_context
+
+    def initialize(lookup_context)
+      @lookup_context = lookup_context
+    end
+
+    def render
+      raise NotImplementedError
+    end
+
+    protected
+
+    def extract_details(options)
+      @lookup_context.registered_details.each_with_object({}) do |key, details|
+        next unless value = options[key]
+        details[key] = Array(value)
+      end
+    end
+
+    def instrument(name, options={})
+      ActiveSupport::Notifications.instrument("render_#{name}.action_view", options){ yield }
+    end
+
+    def prepend_formats(formats)
+      formats = Array(formats)
+      return if formats.empty? || @lookup_context.html_fallback_for_js
+      @lookup_context.formats = formats | @lookup_context.formats
+    end
+  end
+end
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
new file mode 100644
index 0000000000..821026268a
--- /dev/null
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -0,0 +1,492 @@
+require 'thread_safe'
+
+module ActionView
+  # = Action View Partials
+  #
+  # There's also a convenience method for rendering sub templates within the current controller that depends on a
+  # single object (we call this kind of sub templates for partials). It relies on the fact that partials should
+  # follow the naming convention of being prefixed with an underscore -- as to separate them from regular
+  # templates that could be rendered on their own.
+  #
+  # In a template for Advertiser#account:
+  #
+  #  <%= render partial: "account" %>
+  #
+  # This would render "advertiser/_account.html.erb".
+  #
+  # In another template for Advertiser#buy, we could have:
+  #
+  #   <%= render partial: "account", locals: { account: @buyer } %>
+  #
+  #   <% @advertisements.each do |ad| %>
+  #     <%= render partial: "ad", locals: { ad: ad } %>
+  #   <% end %>
+  #
+  # This would first render "advertiser/_account.html.erb" with @buyer passed in as the local variable +account+, then
+  # render "advertiser/_ad.html.erb" and pass the local variable +ad+ to the template for display.
+  #
+  # == The :as and :object options
+  #
+  # By default <tt>ActionView::PartialRenderer</tt> doesn't have any local variables.
+  # The <tt>:object</tt> option can be used to pass an object to the partial. For instance:
+  #
+  #   <%= render partial: "account", object: @buyer %>
+  #
+  # would provide the <tt>@buyer</tt> object to the partial, available under the local variable +account+ and is
+  # equivalent to:
+  #
+  #   <%= render partial: "account", locals: { account: @buyer } %>
+  #
+  # With the <tt>:as</tt> option we can specify a different name for said local variable. For example, if we
+  # wanted it to be +user+ instead of +account+ we'd do:
+  #
+  #   <%= render partial: "account", object: @buyer, as: 'user' %>
+  #
+  # This is equivalent to
+  #
+  #   <%= render partial: "account", locals: { user: @buyer } %>
+  #
+  # == Rendering a collection of partials
+  #
+  # The example of partial use describes a familiar pattern where a template needs to iterate over an array and
+  # render a sub template for each of the elements. This pattern has been implemented as a single method that
+  # accepts an array and renders a partial by the same name as the elements contained within. So the three-lined
+  # example in "Using partials" can be rewritten with a single line:
+  #
+  #   <%= render partial: "ad", collection: @advertisements %>
+  #
+  # This will render "advertiser/_ad.html.erb" and pass the local variable +ad+ to the template for display. An
+  # iteration counter will automatically be made available to the template with a name of the form
+  # +partial_name_counter+. In the case of the example above, the template would be fed +ad_counter+.
+  #
+  # The <tt>:as</tt> option may be used when rendering partials.
+  #
+  # You can specify a partial to be rendered between elements via the <tt>:spacer_template</tt> option.
+  # The following example will render <tt>advertiser/_ad_divider.html.erb</tt> between each ad partial:
+  #
+  #   <%= render partial: "ad", collection: @advertisements, spacer_template: "ad_divider" %>
+  #
+  # If the given <tt>:collection</tt> is nil or empty, <tt>render</tt> will return nil. This will allow you
+  # to specify a text which will displayed instead by using this form:
+  #
+  #   <%= render(partial: "ad", collection: @advertisements) || "There's no ad to be displayed" %>
+  #
+  # NOTE: Due to backwards compatibility concerns, the collection can't be one of hashes. Normally you'd also
+  # just keep domain objects, like Active Records, in there.
+  #
+  # == Rendering shared partials
+  #
+  # Two controllers can share a set of partials and render them like this:
+  #
+  #   <%= render partial: "advertisement/ad", locals: { ad: @advertisement } %>
+  #
+  # This will render the partial "advertisement/_ad.html.erb" regardless of which controller this is being called from.
+  #
+  # == Rendering objects that respond to `to_partial_path`
+  #
+  # Instead of explicitly naming the location of a partial, you can also let PartialRenderer do the work
+  # and pick the proper path by checking `to_partial_path` method.
+  #
+  #  # @account.to_partial_path returns 'accounts/account', so it can be used to replace:
+  #  # <%= render partial: "accounts/account", locals: { account: @account} %>
+  #  <%= render partial: @account %>
+  #
+  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on `to_partial_path`,
+  #  # that's why we can replace:
+  #  # <%= render partial: "posts/post", collection: @posts %>
+  #  <%= render partial: @posts %>
+  #
+  # == Rendering the default case
+  #
+  # If you're not going to be using any of the options like collections or layouts, you can also use the short-hand
+  # defaults of render to render partials. Examples:
+  #
+  #  # Instead of <%= render partial: "account" %>
+  #  <%= render "account" %>
+  #
+  #  # Instead of <%= render partial: "account", locals: { account: @buyer } %>
+  #  <%= render "account", account: @buyer %>
+  #
+  #  # @account.to_partial_path returns 'accounts/account', so it can be used to replace:
+  #  # <%= render partial: "accounts/account", locals: { account: @account} %>
+  #  <%= render @account %>
+  #
+  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on `to_partial_path`,
+  #  # that's why we can replace:
+  #  # <%= render partial: "posts/post", collection: @posts %>
+  #  <%= render @posts %>
+  #
+  # == Rendering partials with layouts
+  #
+  # Partials can have their own layouts applied to them. These layouts are different than the ones that are
+  # specified globally for the entire action, but they work in a similar fashion. Imagine a list with two types
+  # of users:
+  #
+  #   <%# app/views/users/index.html.erb &>
+  #   Here's the administrator:
+  #   <%= render partial: "user", layout: "administrator", locals: { user: administrator } %>
+  #
+  #   Here's the editor:
+  #   <%= render partial: "user", layout: "editor", locals: { user: editor } %>
+  #
+  #   <%# app/views/users/_user.html.erb &>
+  #   Name: <%= user.name %>
+  #
+  #   <%# app/views/users/_administrator.html.erb &>
+  #   <div id="administrator">
+  #     Budget: $<%= user.budget %>
+  #     <%= yield %>
+  #   </div>
+  #
+  #   <%# app/views/users/_editor.html.erb &>
+  #   <div id="editor">
+  #     Deadline: <%= user.deadline %>
+  #     <%= yield %>
+  #   </div>
+  #
+  # ...this will return:
+  #
+  #   Here's the administrator:
+  #   <div id="administrator">
+  #     Budget: $<%= user.budget %>
+  #     Name: <%= user.name %>
+  #   </div>
+  #
+  #   Here's the editor:
+  #   <div id="editor">
+  #     Deadline: <%= user.deadline %>
+  #     Name: <%= user.name %>
+  #   </div>
+  #
+  # If a collection is given, the layout will be rendered once for each item in
+  # the collection. Just think these two snippets have the same output:
+  #
+  #   <%# app/views/users/_user.html.erb %>
+  #   Name: <%= user.name %>
+  #
+  #   <%# app/views/users/index.html.erb %>
+  #   <%# This does not use layouts %>
+  #   <ul>
+  #     <% users.each do |user| -%>
+  #       <li>
+  #         <%= render partial: "user", locals: { user: user } %>
+  #       </li>
+  #     <% end -%>
+  #   </ul>
+  #
+  #   <%# app/views/users/_li_layout.html.erb %>
+  #   <li>
+  #     <%= yield %>
+  #   </li>
+  #
+  #   <%# app/views/users/index.html.erb %>
+  #   <ul>
+  #     <%= render partial: "user", layout: "li_layout", collection: users %>
+  #   </ul>
+  #
+  # Given two users whose names are Alice and Bob, these snippets return:
+  #
+  #   <ul>
+  #     <li>
+  #       Name: Alice
+  #     </li>
+  #     <li>
+  #       Name: Bob
+  #     </li>
+  #   </ul>
+  #
+  # The current object being rendered, as well as the object_counter, will be
+  # available as local variables inside the layout template under the same names
+  # as available in the partial.
+  #
+  # You can also apply a layout to a block within any template:
+  #
+  #   <%# app/views/users/_chief.html.erb &>
+  #   <%= render(layout: "administrator", locals: { user: chief }) do %>
+  #     Title: <%= chief.title %>
+  #   <% end %>
+  #
+  # ...this will return:
+  #
+  #   <div id="administrator">
+  #     Budget: $<%= user.budget %>
+  #     Title: <%= chief.name %>
+  #   </div>
+  #
+  # As you can see, the <tt>:locals</tt> hash is shared between both the partial and its layout.
+  #
+  # If you pass arguments to "yield" then this will be passed to the block. One way to use this is to pass
+  # an array to layout and treat it as an enumerable.
+  #
+  #   <%# app/views/users/_user.html.erb &>
+  #   <div class="user">
+  #     Budget: $<%= user.budget %>
+  #     <%= yield user %>
+  #   </div>
+  #
+  #   <%# app/views/users/index.html.erb &>
+  #   <%= render layout: @users do |user| %>
+  #     Title: <%= user.title %>
+  #   <% end %>
+  #
+  # This will render the layout for each user and yield to the block, passing the user, each time.
+  #
+  # You can also yield multiple times in one layout and use block arguments to differentiate the sections.
+  #
+  #   <%# app/views/users/_user.html.erb &>
+  #   <div class="user">
+  #     <%= yield user, :header %>
+  #     Budget: $<%= user.budget %>
+  #     <%= yield user, :footer %>
+  #   </div>
+  #
+  #   <%# app/views/users/index.html.erb &>
+  #   <%= render layout: @users do |user, section| %>
+  #     <%- case section when :header -%>
+  #       Title: <%= user.title %>
+  #     <%- when :footer -%>
+  #       Deadline: <%= user.deadline %>
+  #     <%- end -%>
+  #   <% end %>
+  class PartialRenderer < AbstractRenderer
+    PREFIXED_PARTIAL_NAMES = ThreadSafe::Cache.new do |h, k|
+      h[k] = ThreadSafe::Cache.new
+    end
+
+    def initialize(*)
+      super
+      @context_prefix = @lookup_context.prefixes.first
+    end
+
+    def render(context, options, block)
+      setup(context, options, block)
+      identifier = (@template = find_partial) ? @template.identifier : @path
+
+      @lookup_context.rendered_format ||= begin
+        if @template && @template.formats.present?
+          @template.formats.first
+        else
+          formats.first
+        end
+      end
+
+      if @collection
+        instrument(:collection, :identifier => identifier || "collection", :count => @collection.size) do
+          render_collection
+        end
+      else
+        instrument(:partial, :identifier => identifier) do
+          render_partial
+        end
+      end
+    end
+
+    def render_collection
+      return nil if @collection.blank?
+
+      if @options.key?(:spacer_template)
+        spacer = find_template(@options[:spacer_template], @locals.keys).render(@view, @locals)
+      end
+
+      result = @template ? collection_with_template : collection_without_template
+      result.join(spacer).html_safe
+    end
+
+    def render_partial
+      view, locals, block = @view, @locals, @block
+      object, as = @object, @variable
+
+      if !block && (layout = @options[:layout])
+        layout = find_template(layout.to_s, @template_keys)
+      end
+
+      object ||= locals[as]
+      locals[as] = object
+
+      content = @template.render(view, locals) do |*name|
+        view._layout_for(*name, &block)
+      end
+
+      content = layout.render(view, locals){ content } if layout
+      content
+    end
+
+    private
+
+    # Sets up instance variables needed for rendering a partial. This method
+    # finds the options and details and extracts them. The method also contains
+    # logic that handles the type of object passed in as the partial.
+    #
+    # If +options[:partial]+ is a string, then the +@path+ instance variable is
+    # set to that string. Otherwise, the +options[:partial]+ object must
+    # respond to +to_partial_path+ in order to setup the path.
+    def setup(context, options, block)
+      @view   = context
+      partial = options[:partial]
+
+      @options = options
+      @locals  = options[:locals] || {}
+      @block   = block
+      @details = extract_details(options)
+
+      prepend_formats(options[:formats])
+
+      if String === partial
+        @object     = options[:object]
+        @path       = partial
+        @collection = collection
+      else
+        @object = partial
+
+        if @collection = collection_from_object || collection
+          paths = @collection_data = @collection.map { |o| partial_path(o) }
+          @path = paths.uniq.size == 1 ? paths.first : nil
+        else
+          @path = partial_path
+        end
+      end
+
+      if as = options[:as]
+        raise_invalid_identifier(as) unless as.to_s =~ /\A[a-z_]\w*\z/
+        as = as.to_sym
+      end
+
+      if @path
+        @variable, @variable_counter = retrieve_variable(@path, as)
+        @template_keys = retrieve_template_keys
+      else
+        paths.map! { |path| retrieve_variable(path, as).unshift(path) }
+      end
+
+      self
+    end
+
+    def collection
+      if @options.key?(:collection)
+        collection = @options[:collection]
+        collection.respond_to?(:to_ary) ? collection.to_ary : []
+      end
+    end
+
+    def collection_from_object
+      @object.to_ary if @object.respond_to?(:to_ary)
+    end
+
+    def find_partial
+      if path = @path
+        find_template(path, @template_keys)
+      end
+    end
+
+    def find_template(path, locals)
+      prefixes = path.include?(?/) ? [] : @lookup_context.prefixes
+      @lookup_context.find_template(path, prefixes, true, locals, @details)
+    end
+
+    def collection_with_template
+      view, locals, template = @view, @locals, @template
+      as, counter = @variable, @variable_counter
+
+      if layout = @options[:layout]
+        layout = find_template(layout, @template_keys)
+      end
+
+      index = -1
+      @collection.map do |object|
+        locals[as]      = object
+        locals[counter] = (index += 1)
+
+        content = template.render(view, locals)
+        content = layout.render(view, locals) { content } if layout
+        content
+      end
+    end
+
+    def collection_without_template
+      view, locals, collection_data = @view, @locals, @collection_data
+      cache = {}
+      keys  = @locals.keys
+
+      index = -1
+      @collection.map do |object|
+        index += 1
+        path, as, counter = collection_data[index]
+
+        locals[as]      = object
+        locals[counter] = index
+
+        template = (cache[path] ||= find_template(path, keys + [as, counter]))
+        template.render(view, locals)
+      end
+    end
+
+    # Obtains the path to where the object's partial is located. If the object
+    # responds to +to_partial_path+, then +to_partial_path+ will be called and
+    # will provide the path. If the object does not respond to +to_partial_path+,
+    # then an +ArgumentError+ is raised.
+    #
+    # If +prefix_partial_path_with_controller_namespace+ is true, then this
+    # method will prefix the partial paths with a namespace.
+    def partial_path(object = @object)
+      object = object.to_model if object.respond_to?(:to_model)
+
+      path = if object.respond_to?(:to_partial_path)
+        object.to_partial_path
+      else
+        raise ArgumentError.new("'#{object.inspect}' is not an ActiveModel-compatible object. It must implement :to_partial_path.")
+      end
+
+      if @view.prefix_partial_path_with_controller_namespace
+        prefixed_partial_names[path] ||= merge_prefix_into_object_path(@context_prefix, path.dup)
+      else
+        path
+      end
+    end
+
+    def prefixed_partial_names
+      @prefixed_partial_names ||= PREFIXED_PARTIAL_NAMES[@context_prefix]
+    end
+
+    def merge_prefix_into_object_path(prefix, object_path)
+      if prefix.include?(?/) && object_path.include?(?/)
+        prefixes = []
+        prefix_array = File.dirname(prefix).split('/')
+        object_path_array = object_path.split('/')[0..-3] # skip model dir & partial
+
+        prefix_array.each_with_index do |dir, index|
+          break if dir == object_path_array[index]
+          prefixes << dir
+        end
+
+        (prefixes << object_path).join("/")
+      else
+        object_path
+      end
+    end
+
+    def retrieve_template_keys
+      keys = @locals.keys
+      keys << @variable         if @object || @collection
+      keys << @variable_counter if @collection
+      keys
+    end
+
+    def retrieve_variable(path, as)
+      variable = as || begin
+        base = path[-1] == "/" ? "" : File.basename(path)
+        raise_invalid_identifier(path) unless base =~ /\A_?([a-z]\w*)(\.\w+)*\z/
+        $1.to_sym
+      end
+      variable_counter = :"#{variable}_counter" if @collection
+      [variable, variable_counter]
+    end
+
+    IDENTIFIER_ERROR_MESSAGE = "The partial name (%s) is not a valid Ruby identifier; " +
+                               "make sure your partial name starts with a lowercase letter or underscore, " +
+                               "and is followed by any combination of letters, numbers and underscores."
+
+    def raise_invalid_identifier(path)
+      raise ArgumentError.new(IDENTIFIER_ERROR_MESSAGE % (path))
+    end
+  end
+end
diff --git a/actionview/lib/action_view/renderer/renderer.rb b/actionview/lib/action_view/renderer/renderer.rb
new file mode 100644
index 0000000000..964b18337e
--- /dev/null
+++ b/actionview/lib/action_view/renderer/renderer.rb
@@ -0,0 +1,50 @@
+module ActionView
+  # This is the main entry point for rendering. It basically delegates
+  # to other objects like TemplateRenderer and PartialRenderer which
+  # actually renders the template.
+  #
+  # The Renderer will parse the options from the +render+ or +render_body+
+  # method and render a partial or a template based on the options. The
+  # +TemplateRenderer+ and +PartialRenderer+ objects are wrappers which do all
+  # the setup and logic necessary to render a view and a new object is created
+  # each time +render+ is called.
+  class Renderer
+    attr_accessor :lookup_context
+
+    def initialize(lookup_context)
+      @lookup_context = lookup_context
+    end
+
+    # Main render entry point shared by AV and AC.
+    def render(context, options)
+      if options.key?(:partial)
+        render_partial(context, options)
+      else
+        render_template(context, options)
+      end
+    end
+
+    # Render but returns a valid Rack body. If fibers are defined, we return
+    # a streaming body that renders the template piece by piece.
+    #
+    # Note that partials are not supported to be rendered with streaming,
+    # so in such cases, we just wrap them in an array.
+    def render_body(context, options)
+      if options.key?(:partial)
+        [render_partial(context, options)]
+      else
+        StreamingTemplateRenderer.new(@lookup_context).render(context, options)
+      end
+    end
+
+    # Direct accessor to template rendering.
+    def render_template(context, options) #:nodoc:
+      TemplateRenderer.new(@lookup_context).render(context, options)
+    end
+
+    # Direct access to partial rendering.
+    def render_partial(context, options, &block) #:nodoc:
+      PartialRenderer.new(@lookup_context).render(context, options, block)
+    end
+  end
+end
diff --git a/actionview/lib/action_view/renderer/streaming_template_renderer.rb b/actionview/lib/action_view/renderer/streaming_template_renderer.rb
new file mode 100644
index 0000000000..9cf6eb0c65
--- /dev/null
+++ b/actionview/lib/action_view/renderer/streaming_template_renderer.rb
@@ -0,0 +1,103 @@
+require 'fiber'
+
+module ActionView
+  # == TODO
+  #
+  # * Support streaming from child templates, partials and so on.
+  # * Integrate exceptions with exceptron
+  # * Rack::Cache needs to support streaming bodies
+  class StreamingTemplateRenderer < TemplateRenderer #:nodoc:
+    # A valid Rack::Body (i.e. it responds to each).
+    # It is initialized with a block that, when called, starts
+    # rendering the template.
+    class Body #:nodoc:
+      def initialize(&start)
+        @start = start
+      end
+
+      def each(&block)
+        begin
+          @start.call(block)
+        rescue Exception => exception
+          log_error(exception)
+          block.call ActionView::Base.streaming_completion_on_exception
+        end
+        self
+      end
+
+      private
+
+      # This is the same logging logic as in ShowExceptions middleware.
+      # TODO Once "exceptron" is in, refactor this piece to simply re-use exceptron.
+      def log_error(exception) #:nodoc:
+        logger = ActionView::Base.logger
+        return unless logger
+
+        message = "\n#{exception.class} (#{exception.message}):\n"
+        message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
+        message << "  " << exception.backtrace.join("\n  ")
+        logger.fatal("#{message}\n\n")
+      end
+    end
+
+    # For streaming, instead of rendering a given a template, we return a Body
+    # object that responds to each. This object is initialized with a block
+    # that knows how to render the template.
+    def render_template(template, layout_name = nil, locals = {}) #:nodoc:
+      return [super] unless layout_name && template.supports_streaming?
+
+      locals ||= {}
+      layout   = layout_name && find_layout(layout_name, locals.keys)
+
+      Body.new do |buffer|
+        delayed_render(buffer, template, layout, @view, locals)
+      end
+    end
+
+    private
+
+    def delayed_render(buffer, template, layout, view, locals)
+      # Wrap the given buffer in the StreamingBuffer and pass it to the
+      # underlying template handler. Now, everytime something is concatenated
+      # to the buffer, it is not appended to an array, but streamed straight
+      # to the client.
+      output  = ActionView::StreamingBuffer.new(buffer)
+      yielder = lambda { |*name| view._layout_for(*name) }
+
+      instrument(:template, :identifier => template.identifier, :layout => layout.try(:virtual_path)) do
+        fiber = Fiber.new do
+          if layout
+            layout.render(view, locals, output, &yielder)
+          else
+            # If you don't have a layout, just render the thing
+            # and concatenate the final result. This is the same
+            # as a layout with just <%= yield %>
+            output.safe_concat view._layout_for
+          end
+        end
+
+        # Set the view flow to support streaming. It will be aware
+        # when to stop rendering the layout because it needs to search
+        # something in the template and vice-versa.
+        view.view_flow = StreamingFlow.new(view, fiber)
+
+        # Yo! Start the fiber!
+        fiber.resume
+
+        # If the fiber is still alive, it means we need something
+        # from the template, so start rendering it. If not, it means
+        # the layout exited without requiring anything from the template.
+        if fiber.alive?
+          content = template.render(view, locals, &yielder)
+
+          # Once rendering the template is done, sets its content in the :layout key.
+          view.view_flow.set(:layout, content)
+
+          # In case the layout continues yielding, we need to resume
+          # the fiber until all yields are handled.
+          fiber.resume while fiber.alive?
+        end
+      end
+    end
+  end
+end
diff --git a/actionview/lib/action_view/renderer/template_renderer.rb b/actionview/lib/action_view/renderer/template_renderer.rb
new file mode 100644
index 0000000000..4d5c5db80c
--- /dev/null
+++ b/actionview/lib/action_view/renderer/template_renderer.rb
@@ -0,0 +1,96 @@
+require 'active_support/core_ext/object/try'
+
+module ActionView
+  class TemplateRenderer < AbstractRenderer #:nodoc:
+    def render(context, options)
+      @view    = context
+      @details = extract_details(options)
+      template = determine_template(options)
+      context  = @lookup_context
+
+      prepend_formats(template.formats)
+
+      unless context.rendered_format
+        context.rendered_format = template.formats.first || formats.last
+      end
+
+      render_template(template, options[:layout], options[:locals])
+    end
+
+    # Determine the template to be rendered using the given options.
+    def determine_template(options) #:nodoc:
+      keys = options.fetch(:locals, {}).keys
+
+      if options.key?(:text)
+        Template::Text.new(options[:text], formats.first)
+      elsif options.key?(:file)
+        with_fallbacks { find_template(options[:file], nil, false, keys, @details) }
+      elsif options.key?(:inline)
+        handler = Template.handler_for_extension(options[:type] || "erb")
+        Template.new(options[:inline], "inline template", handler, :locals => keys)
+      elsif options.key?(:template)
+        if options[:template].respond_to?(:render)
+          options[:template]
+        else
+          find_template(options[:template], options[:prefixes], false, keys, @details)
+        end
+      else
+        raise ArgumentError, "You invoked render but did not give any of :partial, :template, :inline, :file or :text option."
+      end
+    end
+
+    # Renders the given template. A string representing the layout can be
+    # supplied as well.
+    def render_template(template, layout_name = nil, locals = nil) #:nodoc:
+      view, locals = @view, locals || {}
+
+      render_with_layout(layout_name, locals) do |layout|
+        instrument(:template, :identifier => template.identifier, :layout => layout.try(:virtual_path)) do
+          template.render(view, locals) { |*name| view._layout_for(*name) }
+        end
+      end
+    end
+
+    def render_with_layout(path, locals) #:nodoc:
+      layout  = path && find_layout(path, locals.keys)
+      content = yield(layout)
+
+      if layout
+        view = @view
+        view.view_flow.set(:layout, content)
+        layout.render(view, locals){ |*name| view._layout_for(*name) }
+      else
+        content
+      end
+    end
+
+    # This is the method which actually finds the layout using details in the lookup
+    # context object. If no layout is found, it checks if at least a layout with
+    # the given name exists across all details before raising the error.
+    def find_layout(layout, keys)
+      with_layout_format { resolve_layout(layout, keys) }
+    end
+
+    def resolve_layout(layout, keys)
+      case layout
+      when String
+        begin
+          if layout =~ /^\//
+            with_fallbacks { find_template(layout, nil, false, keys, @details) }
+          else
+            find_template(layout, nil, false, keys, @details)
+          end
+        rescue ActionView::MissingTemplate
+          all_details = @details.merge(:formats => @lookup_context.default_formats)
+          raise unless template_exists?(layout, nil, false, keys, all_details)
+        end
+      when Proc
+        resolve_layout(layout.call, keys)
+      when FalseClass
+        nil
+      else
+        layout
+      end
+    end
+  end
+end