Yo dawg, I heard you like streaming. So I put a fiber, inside a block, inside a body, so you can stream.

13 files changed, 235 insertions, 111 deletions

diff --git a/actionpack/lib/action_view.rb b/actionpack/lib/action_view.rb
index 9b8b694646..4547aceb28 100644
--- a/actionpack/lib/action_view.rb
+++ b/actionpack/lib/action_view.rb
@@ -44,7 +44,7 @@ module ActionView
       autoload :AbstractRenderer
       autoload :PartialRenderer
       autoload :TemplateRenderer
-      autoload :FiberedTemplateRenderer
+      autoload :StreamingTemplateRenderer
     end
 
     autoload_at "action_view/template/resolver" do
@@ -54,6 +54,16 @@ module ActionView
       autoload :FallbackFileSystemResolver
     end
 
+    autoload_at "action_view/buffers" do
+      autoload :OutputBuffer
+      autoload :StreamingBuffer
+    end
+
+    autoload_at "action_view/flows" do
+      autoload :OutputFlow
+      autoload :StreamingFlow
+    end
+
     autoload_at "action_view/template/error" do
       autoload :MissingTemplate
       autoload :ActionViewError
diff --git a/actionpack/lib/action_view/base.rb b/actionpack/lib/action_view/base.rb
index 10a523eeac..513080ae54 100644
--- a/actionpack/lib/action_view/base.rb
+++ b/actionpack/lib/action_view/base.rb
@@ -182,7 +182,7 @@ module ActionView #:nodoc:
 
       @_config = {}
       @_virtual_path = nil
-      @_view_flow = Flow.new
+      @_view_flow = OutputFlow.new
       @output_buffer = nil
 
       if @_controller = controller
@@ -205,49 +205,4 @@ module ActionView #:nodoc:
 
     ActiveSupport.run_load_hooks(:action_view, self)
   end
-
-  class Flow
-    attr_reader :content
-
-    def initialize
-      @content = Hash.new { |h,k| h[k] = ActiveSupport::SafeBuffer.new }
-    end
-
-    def get(key)
-      @content[key]
-    end
-
-    def set(key, value)
-      @content[key] = value
-    end
-
-    def append(key, value)
-      @content[key] << value
-    end
-  end
-
-  class FiberedFlow < Flow
-    def initialize(flow, fiber)
-      @content = flow.content
-      @fiber   = fiber
-    end
-
-    def get(key)
-      return super if @content.key?(key)
-
-      begin
-        @waiting_for = key
-        Fiber.yield
-      ensure
-        @waiting_for = nil
-      end
-
-      super
-    end
-
-    def set(key, value)
-      super
-      @fiber.resume if @waiting_for == key
-    end
-  end
 end
diff --git a/actionpack/lib/action_view/buffers.rb b/actionpack/lib/action_view/buffers.rb
new file mode 100644
index 0000000000..2e2b39e4a2
--- /dev/null
+++ b/actionpack/lib/action_view/buffers.rb
@@ -0,0 +1,43 @@
+require 'active_support/core_ext/string/output_safety'
+
+module ActionView
+  class OutputBuffer < ActiveSupport::SafeBuffer
+    def initialize(*)
+      super
+      encode! if encoding_aware?
+    end
+
+    def <<(value)
+      super(value.to_s)
+    end
+    alias :append= :<<
+    alias :safe_append= :safe_concat
+  end
+
+  class StreamingBuffer
+    def initialize(block)
+      @block = block
+    end
+
+    def <<(value)
+      value = value.to_s
+      value = ERB::Util.h(value) unless value.html_safe?
+      @block.call(value)
+    end
+    alias :concat  :<<
+    alias :append= :<<
+
+    def safe_concat(value)
+      @block.call(value.to_s)
+    end
+    alias :safe_append= :safe_concat
+
+    def html_safe?
+      true
+    end
+    
+    def html_safe
+      self
+    end
+  end
+end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/flows.rb b/actionpack/lib/action_view/flows.rb
new file mode 100644
index 0000000000..1ac62961d1
--- /dev/null
+++ b/actionpack/lib/action_view/flows.rb
@@ -0,0 +1,64 @@
+require 'active_support/core_ext/string/output_safety'
+
+module ActionView
+  class OutputFlow
+    attr_reader :content
+
+    def initialize
+      @content = Hash.new { |h,k| h[k] = ActiveSupport::SafeBuffer.new }
+    end
+
+    def get(key)
+      @content[key]
+    end
+
+    def set(key, value)
+      @content[key] = value
+    end
+
+    def append(key, value)
+      @content[key] << value
+    end
+  end
+
+  class StreamingFlow < OutputFlow
+    def initialize(flow, fiber)
+      @content = flow.content
+      @fiber   = fiber
+      @root    = Fiber.current.object_id
+    end
+
+    # Try to get an stored content. If the content
+    # is not available and we are inside the layout
+    # fiber, we set that we are waiting for the given
+    # key and yield.
+    def get(key)
+      return super if @content.key?(key)
+
+      if inside_fiber?
+        begin
+          @waiting_for = key
+          Fiber.yield
+        ensure
+          @waiting_for = nil
+        end
+      end
+
+      super
+    end
+
+    # Set the contents for the given key. This is called
+    # by provides and resumes back to the fiber if it is
+    # the key it is waiting for.
+    def set(key, value)
+      super
+      @fiber.resume if @waiting_for == key
+    end
+
+    private
+
+    def inside_fiber?
+      Fiber.current.object_id != @root
+    end
+  end
+end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/helpers/capture_helper.rb b/actionpack/lib/action_view/helpers/capture_helper.rb
index f8b5605ed9..148d814ac7 100644
--- a/actionpack/lib/action_view/helpers/capture_helper.rb
+++ b/actionpack/lib/action_view/helpers/capture_helper.rb
@@ -139,6 +139,17 @@ module ActionView
         result unless content
       end
 
+      # The same as +content_for+ but when used with streaming flushes
+      # straight back to the layout. In other words, if you want to
+      # concatenate several times to the same buffer when rendering a given
+      # template, you should use +content_for+, if not, use +provide+ as it
+      # has better streaming support.
+      def provide(name, content = nil, &block)
+        content = capture(&block) if block_given?
+        @_view_flow.set(name, content) if content
+        content
+      end
+
       # content_for? simply checks whether any content has been captured yet using content_for
       # Useful to render parts of your layout differently based on what is in your views.
       #
diff --git a/actionpack/lib/action_view/renderer/fibered_template_renderer.rb b/actionpack/lib/action_view/renderer/fibered_template_renderer.rb
deleted file mode 100644
index 45f48cab76..0000000000
--- a/actionpack/lib/action_view/renderer/fibered_template_renderer.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require 'action_view/renderer/template_renderer'
-require 'fiber'
-
-module ActionView
-  class FiberedTemplateRenderer < TemplateRenderer #:nodoc:
-    # Renders the given template. An string representing the layout can be
-    # supplied as well.
-    def render_template(template, layout_name = nil, locals = {}) #:nodoc:
-      view, locals = @view, locals || {}
-
-      final = nil
-      layout  = layout_name && find_layout(layout_name, locals.keys)
-      yielder = lambda { |*name| view._layout_for(*name) }
-
-      instrument(:template, :identifier => template.identifier, :layout => layout.try(:virtual_path)) do
-        @fiber = Fiber.new do
-          final = if layout
-            layout.render(view, locals, &yielder)
-          else
-            view._layout_for
-          end
-        end
-
-        @view._view_flow = FiberedFlow.new(view._view_flow, @fiber)
-        @fiber.resume
-
-        content = template.render(view, locals, &yielder)
-        view._view_flow.set(:layout, content)
-        @fiber.resume while @fiber.alive?
-      end
-
-      final
-    end
-  end
-end
diff --git a/actionpack/lib/action_view/renderer/partial_renderer.rb b/actionpack/lib/action_view/renderer/partial_renderer.rb
index 180afc27ac..10cd37d56f 100644
--- a/actionpack/lib/action_view/renderer/partial_renderer.rb
+++ b/actionpack/lib/action_view/renderer/partial_renderer.rb
@@ -1,5 +1,3 @@
-require 'action_view/renderer/abstract_renderer'
-
 module ActionView
   class PartialRenderer < AbstractRenderer #:nodoc:
     PARTIAL_NAMES = Hash.new {|h,k| h[k] = {} }
diff --git a/actionpack/lib/action_view/renderer/streaming_template_renderer.rb b/actionpack/lib/action_view/renderer/streaming_template_renderer.rb
new file mode 100644
index 0000000000..a8c6ecbde1
--- /dev/null
+++ b/actionpack/lib/action_view/renderer/streaming_template_renderer.rb
@@ -0,0 +1,79 @@
+require 'fiber'
+
+module ActionView
+  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)
+        @start.call(block)
+        self
+      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 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._view_flow, 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/actionpack/lib/action_view/renderer/template_renderer.rb b/actionpack/lib/action_view/renderer/template_renderer.rb
index 10d8cc3b87..6b5ead463f 100644
--- a/actionpack/lib/action_view/renderer/template_renderer.rb
+++ b/actionpack/lib/action_view/renderer/template_renderer.rb
@@ -1,6 +1,5 @@
 require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/array/wrap'
-require 'action_view/renderer/abstract_renderer'
 
 module ActionView
   class TemplateRenderer < AbstractRenderer #:nodoc:
diff --git a/actionpack/lib/action_view/rendering.rb b/actionpack/lib/action_view/rendering.rb
index e3568e70e5..2bce2fb045 100644
--- a/actionpack/lib/action_view/rendering.rb
+++ b/actionpack/lib/action_view/rendering.rb
@@ -27,6 +27,19 @@ module ActionView
       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(options)
+      if options.key?(:partial)
+        [_render_partial(options)]
+      else
+        StreamingTemplateRenderer.new(self).render(options)
+      end
+    end
+
     # Returns the contents that are yielded to a layout, given a name or a block.
     #
     # You can think of a layout as a method that is called with a block. If the user calls
@@ -79,7 +92,7 @@ module ActionView
       @_view_flow.get(name).html_safe
     end
 
-    # Returns the content from the Flow unless we have a block.
+    # Handle layout for calls from partials that supports blocks.
     def _block_layout_for(*args, &block)
       name = args.first
 
@@ -91,20 +104,11 @@ module ActionView
     end
 
     def _render_template(options) #:nodoc:
-      if @magic_medicine
-        _fibered_template_renderer.render(options)
-      else
-        _template_renderer.render(options)
-      end
+      _template_renderer.render(options)
     end
 
     def _template_renderer #:nodoc:
       @_template_renderer ||= TemplateRenderer.new(self)
     end
-
-    def _fibered_template_renderer #:nodoc:
-      @_fibered_template_renderer ||= FiberedTemplateRenderer.new(self)
-    end
-
   end
 end
diff --git a/actionpack/lib/action_view/template.rb b/actionpack/lib/action_view/template.rb
index 17e549a1c2..6dfc4f68ae 100644
--- a/actionpack/lib/action_view/template.rb
+++ b/actionpack/lib/action_view/template.rb
@@ -126,6 +126,12 @@ module ActionView
       @formats = Array.wrap(format).map { |f| f.is_a?(Mime::Type) ? f.ref : f }
     end
 
+    # Returns if the underlying handler supports streaming. If so,
+    # a streaming buffer *may* be passed when it start rendering.
+    def supports_streaming?
+      handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
+    end
+
     # Render a template. If the template was not compiled yet, it is done
     # exactly before rendering.
     #
diff --git a/actionpack/lib/action_view/template/handlers/erb.rb b/actionpack/lib/action_view/template/handlers/erb.rb
index 4af576a688..7e9e4e518a 100644
--- a/actionpack/lib/action_view/template/handlers/erb.rb
+++ b/actionpack/lib/action_view/template/handlers/erb.rb
@@ -1,23 +1,9 @@
 require 'active_support/core_ext/class/attribute_accessors'
-require 'active_support/core_ext/string/output_safety'
 require 'action_view/template'
 require 'action_view/template/handler'
 require 'erubis'
 
 module ActionView
-  class OutputBuffer < ActiveSupport::SafeBuffer
-    def initialize(*)
-      super
-      encode! if encoding_aware?
-    end
-
-    def <<(value)
-      super(value.to_s)
-    end
-    alias :append= :<<
-    alias :safe_append= :safe_concat
-  end
-
   class Template
     module Handlers
       class Erubis < ::Erubis::Eruby
@@ -73,6 +59,10 @@ module ActionView
           new.call(template)
         end
 
+        def supports_streaming?
+          true
+        end
+
         def handles_encoding?
           true
         end
diff --git a/actionpack/test/template/capture_helper_test.rb b/actionpack/test/template/capture_helper_test.rb
index ec252fa117..3ebcb8165f 100644
--- a/actionpack/test/template/capture_helper_test.rb
+++ b/actionpack/test/template/capture_helper_test.rb
@@ -4,7 +4,7 @@ class CaptureHelperTest < ActionView::TestCase
   def setup
     super
     @av = ActionView::Base.new
-    @_view_flow = ActionView::Flow.new
+    @_view_flow = ActionView::OutputFlow.new
   end
 
   def test_capture_captures_the_temporary_output_buffer_in_its_block