5 files changed, 72 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch.rb b/actionpack/lib/action_dispatch.rb
index 38aaa6146e..11cd812695 100644
--- a/actionpack/lib/action_dispatch.rb
+++ b/actionpack/lib/action_dispatch.rb
@@ -39,6 +39,7 @@ module ActionDispatch
   autoload :Rescue, 'action_dispatch/middleware/rescue'
   autoload :ShowExceptions, 'action_dispatch/middleware/show_exceptions'
   autoload :Static, 'action_dispatch/middleware/static'
+  autoload :StringCoercion, 'action_dispatch/middleware/string_coercion'
 
   autoload :Assertions, 'action_dispatch/testing/assertions'
   autoload :Integration, 'action_dispatch/testing/integration'
diff --git a/actionpack/lib/action_dispatch/middleware/string_coercion.rb b/actionpack/lib/action_dispatch/middleware/string_coercion.rb
new file mode 100644
index 0000000000..232e947835
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/string_coercion.rb
@@ -0,0 +1,29 @@
+module ActionDispatch
+  class StringCoercion
+    class UglyBody < ActiveSupport::BasicObject
+      def initialize(body)
+        @body = body
+      end
+
+      def each
+        @body.each do |part|
+          yield part.to_s
+        end
+      end
+
+      private
+        def method_missing(*args, &block)
+          @body.__send__(*args, &block)
+        end
+    end
+
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      status, headers, body = @app.call(env)
+      [status, headers, UglyBody.new(body)]
+    end
+  end
+end
diff --git a/actionpack/test/abstract_unit.rb b/actionpack/test/abstract_unit.rb
index 1214d608a4..4820f00aa1 100644
--- a/actionpack/test/abstract_unit.rb
+++ b/actionpack/test/abstract_unit.rb
@@ -93,6 +93,7 @@ end
 class ActionController::IntegrationTest < ActiveSupport::TestCase
   def self.build_app(routes = nil)
     ActionDispatch::MiddlewareStack.new { |middleware|
+      middleware.use "ActionDispatch::StringCoercion"
       middleware.use "ActionDispatch::ShowExceptions"
       middleware.use "ActionDispatch::Callbacks"
       middleware.use "ActionDispatch::ParamsParser"
diff --git a/actionpack/test/dispatch/string_coercion_test.rb b/actionpack/test/dispatch/string_coercion_test.rb
new file mode 100644
index 0000000000..d79b17b932
--- /dev/null
+++ b/actionpack/test/dispatch/string_coercion_test.rb
@@ -0,0 +1,40 @@
+require 'abstract_unit'
+
+class StringCoercionTest < ActiveSupport::TestCase
+  test "body responds to each" do
+    original_body = []
+    body = ActionDispatch::StringCoercion::UglyBody.new(original_body)
+
+    assert original_body.respond_to?(:each)
+    assert body.respond_to?(:each)
+  end
+
+  test "body responds to to_path" do
+    original_body = []
+    def original_body.to_path; end
+    body = ActionDispatch::StringCoercion::UglyBody.new(original_body)
+
+    assert original_body.respond_to?(:to_path)
+    assert body.respond_to?(:to_path)
+  end
+
+  test "body does not responds to to_path" do
+    original_body = []
+    body = ActionDispatch::StringCoercion::UglyBody.new(original_body)
+
+    assert !original_body.respond_to?(:to_path)
+    assert !body.respond_to?(:to_path)
+  end
+
+  test "calls to_s on body parts" do
+    app = lambda { |env|
+      [200, {'Content-Type' => 'html'}, [1, 2, 3]]
+    }
+    app = ActionDispatch::StringCoercion.new(app)
+    parts = []
+    status, headers, body = app.call({})
+    body.each { |part| parts << part }
+
+    assert_equal %w( 1 2 3 ), parts
+  end
+end
diff --git a/railties/lib/rails/initializer.rb b/railties/lib/rails/initializer.rb
index 2d63ac4d39..c2d6e1609f 100644
--- a/railties/lib/rails/initializer.rb
+++ b/railties/lib/rails/initializer.rb
@@ -271,6 +271,7 @@ module Rails
       configuration.middleware.use(ActionDispatch::ParamsParser)
       configuration.middleware.use(::Rack::MethodOverride)
       configuration.middleware.use(::Rack::Head)
+      configuration.middleware.use(ActionDispatch::StringCoercion)
     end
   end