Action Pack Variants

By default, variants in the templates will be picked up if a variant is set
and there's a match. The format will be:

  app/views/projects/show.html.erb
  app/views/projects/show.html+tablet.erb
  app/views/projects/show.html+phone.erb

If request.variant = :tablet is set, we'll automatically be rendering the
html+tablet template.

In the controller, we can also tailer to the variants with this syntax:

  class ProjectsController < ActionController::Base
    def show
      respond_to do |format|
        format.html do |html|
          @stars = @project.stars

          html.tablet { @notifications = @project.notifications }
          html.phone  { @chat_heads    = @project.chat_heads }
        end

        format.js
        format.atom
      end
    end
  end

The variant itself is nil by default, but can be set in before filters, like
so:

  class ApplicationController < ActionController::Base
    before_action do
      if request.user_agent =~ /iPad/
        request.variant = :tablet
      end
    end
  end

This is modeled loosely on custom mime types, but it's specifically not
intended to be used together. If you're going to make a custom mime type,
you don't need a variant. Variants are for variations on a single mime
types.

6 files changed, 25 insertions, 12 deletions

diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index c6ff683827..e07d9b6314 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -52,6 +52,7 @@ module ActionView
       locales
     end
     register_detail(:formats) { ActionView::Base.default_formats || [:html, :text, :js, :css,  :xml, :json] }
+    register_detail(:variants) { [] }
     register_detail(:handlers){ Template::Handlers.extensions }
 
     class DetailsKey #:nodoc:
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 82db9e26df..99b95fdfb7 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -88,10 +88,14 @@ module ActionView
 
     private
 
-      # Find and renders a template based on the options given.
+      # Find and render a template based on the options given.
       # :api: private
       def _render_template(options) #:nodoc:
+        variant = options[:variant]
+
         lookup_context.rendered_format = nil if options[:formats]
+        lookup_context.variants = [variant] if variant
+
         view_renderer.render(view_context, options)
       end
 
diff --git a/actionview/lib/action_view/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index 3279f068c9..3a3b74cdd5 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -162,8 +162,8 @@ module ActionView
 
   # An abstract class that implements a Resolver with path semantics.
   class PathResolver < Resolver #:nodoc:
-    EXTENSIONS = [:locale, :formats, :handlers]
-    DEFAULT_PATTERN = ":prefix/:action{.:locale,}{.:formats,}{.:handlers,}"
+    EXTENSIONS = { :locale => ".", :formats => ".", :variants => "+", :handlers => "." }
+    DEFAULT_PATTERN = ":prefix/:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}"
 
     def initialize(pattern=nil)
       @pattern = pattern || DEFAULT_PATTERN
@@ -240,7 +240,9 @@ module ActionView
       end
 
       handler = Template.handler_for_extension(extension)
-      format  = pieces.last && Template::Types[pieces.last]
+      format  = pieces.last && pieces.last.split(EXTENSIONS[:variants], 2).first # remove variant from format
+      format  &&= Template::Types[format]
+
       [handler, format]
     end
   end
@@ -303,12 +305,13 @@ module ActionView
   # An Optimized resolver for Rails' most common case.
   class OptimizedFileSystemResolver < FileSystemResolver #:nodoc:
     def build_query(path, details)
-      exts = EXTENSIONS.map { |ext| details[ext] }
       query = escape_entry(File.join(@path, path))
 
-      query + exts.map { |ext|
-        "{#{ext.compact.uniq.map { |e| ".#{e}," }.join}}"
-      }.join
+      exts = EXTENSIONS.map do |ext, prefix|
+        "{#{details[ext].compact.uniq.map { |e| "#{prefix}#{e}," }.join}}"
+      end.join
+
+      query + exts
     end
   end
 
diff --git a/actionview/lib/action_view/testing/resolvers.rb b/actionview/lib/action_view/testing/resolvers.rb
index 7afa2fa613..af53ad3b25 100644
--- a/actionview/lib/action_view/testing/resolvers.rb
+++ b/actionview/lib/action_view/testing/resolvers.rb
@@ -21,7 +21,7 @@ module ActionView #:nodoc:
 
     def query(path, exts, formats)
       query = ""
-      EXTENSIONS.each do |ext|
+      EXTENSIONS.each_key do |ext|
         query << '(' << exts[ext].map {|e| e && Regexp.escape(".#{e}") }.join('|') << '|)'
       end
       query = /^(#{Regexp.escape(path)})#{query}$/
diff --git a/actionview/test/template/lookup_context_test.rb b/actionview/test/template/lookup_context_test.rb
index a6a3d6279e..ce9485e146 100644
--- a/actionview/test/template/lookup_context_test.rb
+++ b/actionview/test/template/lookup_context_test.rb
@@ -36,6 +36,11 @@ class LookupContextTest < ActiveSupport::TestCase
     assert @lookup_context.formats.frozen?
   end
 
+  test "provides getters and setters for variants" do
+    @lookup_context.variants = [:mobile]
+    assert_equal [:mobile], @lookup_context.variants
+  end
+
   test "provides getters and setters for formats" do
     @lookup_context.formats = [:html]
     assert_equal [:html], @lookup_context.formats
@@ -254,7 +259,7 @@ class TestMissingTemplate < ActiveSupport::TestCase
 
   test "if a single prefix is passed as a string and the lookup fails, MissingTemplate accepts it" do
     e = assert_raise ActionView::MissingTemplate do
-      details = {:handlers=>[], :formats=>[], :locale=>[]}
+      details = {:handlers=>[], :formats=>[], :variants=>[], :locale=>[]}
       @lookup_context.view_paths.find("foo", "parent", true, details)
     end
     assert_match %r{Missing partial parent/_foo with .* Searched in:\n  \* "/Path/to/views"\n}, e.message
diff --git a/actionview/test/template/testing/fixture_resolver_test.rb b/actionview/test/template/testing/fixture_resolver_test.rb
index 9649f349cb..d6cfa997cd 100644
--- a/actionview/test/template/testing/fixture_resolver_test.rb
+++ b/actionview/test/template/testing/fixture_resolver_test.rb
@@ -3,13 +3,13 @@ require 'abstract_unit'
 class FixtureResolverTest < ActiveSupport::TestCase
   def test_should_return_empty_list_for_unknown_path
     resolver = ActionView::FixtureResolver.new()
-    templates = resolver.find_all("path", "arbitrary", false, {:locale => [], :formats => [:html], :handlers => []})
+    templates = resolver.find_all("path", "arbitrary", false, {:locale => [], :formats => [:html], :variants => [], :handlers => []})
     assert_equal [], templates, "expected an empty list of templates"
   end
 
   def test_should_return_template_for_declared_path
     resolver = ActionView::FixtureResolver.new("arbitrary/path.erb" => "this text")
-    templates = resolver.find_all("path", "arbitrary", false, {:locale => [], :formats => [:html], :handlers => [:erb]})
+    templates = resolver.find_all("path", "arbitrary", false, {:locale => [], :formats => [:html], :variants => [], :handlers => [:erb]})
     assert_equal 1, templates.size, "expected one template"
     assert_equal "this text",      templates.first.source
     assert_equal "arbitrary/path", templates.first.virtual_path