Inline variants syntax

In most cases, when setting variant specific code, you're not sharing any code
within format.

Inline syntax can vastly simplify defining variants in those situations:

  respond_to do |format|
    format.js { render "trash" }
    format.html do |variant|
      variant.phone { redirect_to progress_path }
      variant.none  { render "trash" }
    end
  end

Becomes:

  respond_to do |format|
    format.js         { render "trash" }
    format.html.phone { redirect_to progress_path }
    format.html.none  { render "trash" }
  end

actionpack/lib/action_controller/metal/mime_responds.rb

@@ -445,12 +445,18 @@ def any(*args, &block)
 
       def custom(mime_type, &block)
         mime_type = Mime::Type.lookup(mime_type.to_s) unless mime_type.is_a?(Mime::Type)
-        @responses[mime_type] ||= block
+        @responses[mime_type] ||= if block_given?
+          block
+        else
+          VariantCollector.new
+        end
       end
 
       def response(variant)
         response = @responses.fetch(format, @responses[Mime::ALL])
-        if response.nil? || response.arity == 0
+        if response.is_a?(VariantCollector)
+          response.variant(variant)
+        elsif response.nil? || response.arity == 0
           response
         else
           lambda { response.call VariantFilter.new(variant) }
@@ -461,6 +467,22 @@ def negotiate_format(request)
         @format = request.negotiate_mime(@responses.keys)
       end
 
+      #Used for inline syntax
+      class VariantCollector #:nodoc:
+        def initialize
+          @variants = {}
+        end
+
+        def method_missing(name, *args, &block)
+          @variants[name] = block if block_given?
+        end
+
+        def variant(name)
+          @variants[name.nil? ? :none : name]
+        end
+      end
+
+      #Used for nested block syntax
       class VariantFilter #:nodoc:
         def initialize(variant)
           @variant = variant

actionpack/test/controller/mime/respond_to_test.rb

@@ -175,6 +175,22 @@ def variant_plus_none_for_format
     end
   end
 
+  def variant_inline_syntax
+    respond_to do |format|
+      format.js         { render text: "js"    }
+      format.html.none  { render text: "none"  }
+      format.html.phone { render text: "phone" }
+    end
+  end
+
+  def variant_inline_syntax_without_block
+    respond_to do |format|
+      format.js
+      format.html.none
+      format.html.phone
+    end
+  end
+
   protected
     def set_layout
       case action_name
@@ -554,10 +570,31 @@ def test_multiple_variants_for_format
     assert_equal "tablet", @response.body
   end
 
-
   def test_no_variant_in_variant_setup
     get :variant_plus_none_for_format
     assert_equal "text/html", @response.content_type
     assert_equal "none", @response.body
   end
+
+  def test_variant_inline_syntax
+    get :variant_inline_syntax, format: :js
+    assert_equal "text/javascript", @response.content_type
+    assert_equal "js", @response.body
+
+    get :variant_inline_syntax
+    assert_equal "text/html", @response.content_type
+    assert_equal "none", @response.body
+
+    @request.variant = :phone
+    get :variant_inline_syntax
+    assert_equal "text/html", @response.content_type
+    assert_equal "phone", @response.body
+  end
+
+  def test_variant_inline_syntax_without_block
+    @request.variant = :phone
+    get :variant_inline_syntax_without_block
+    assert_equal "text/html", @response.content_type
+    assert_equal "phone", @response.body
+  end
 end

actionpack/test/fixtures/respond_to/variant_inline_syntax_without_block.html+phone.erb

+phone
\ No newline at end of file