use Array#join so that file encoding doesn't impact returned string.

Fixes #3957

2 files changed, 12 insertions, 3 deletions

diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index fc840668d5..5797c63924 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -111,9 +111,9 @@ module ActionDispatch # :nodoc:
     end
 
     def body
-      str = ''
-      each { |part| str << part.to_s }
-      str
+      strings = []
+      each { |part| strings << part.to_s }
+      strings.join
     end
 
     EMPTY = " "
diff --git a/actionpack/test/dispatch/response_test.rb b/actionpack/test/dispatch/response_test.rb
index 337ece6b88..9bdd5ecbc6 100644
--- a/actionpack/test/dispatch/response_test.rb
+++ b/actionpack/test/dispatch/response_test.rb
@@ -5,6 +5,15 @@ class ResponseTest < ActiveSupport::TestCase
     @response = ActionDispatch::Response.new
   end
 
+  def test_response_body_encoding
+    # FIXME: remove this conditional on Rails 4.0
+    return unless "<3".encoding_aware?
+
+    body = ["hello".encode('utf-8')]
+    response = ActionDispatch::Response.new 200, {}, body
+    assert_equal Encoding::UTF_8, response.body.encoding
+  end
+
   test "simple output" do
     @response.body = "Hello, World!"