Return same string object when no interpolations were made

Author: fatkodima

lib/i18n/interpolate/ruby.rb

@@ -28,7 +28,11 @@ def interpolate(string, values)
 
     def interpolate_hash(string, values)
       pattern = INTERPOLATION_PATTERNS_CACHE[config.interpolation_patterns]
-      string.gsub(pattern) do |match|
+      interpolated = false
+
+      interpolated_string = string.gsub(pattern) do |match|
+        interpolated = true
+
         if match == '%%'
           '%'
         else
@@ -42,6 +46,8 @@ def interpolate_hash(string, values)
           $3 ? sprintf("%#{$3}", value) : value
         end
       end
+
+      interpolated ? interpolated_string : string
     end
   end
 end

test/i18n/interpolate_test.rb

@@ -65,9 +65,15 @@ def gsub(*args, &block)
     end
 
   end
+
   test "with String subclass that redefined gsub method" do
     assert_equal "Hello mars world", I18n.interpolate(RailsSafeBuffer.new("Hello %{planet} world"), :planet => 'mars') 
   end
+
+  test "with String subclass that redefined gsub method returns same object if no interpolations" do
+    string = RailsSafeBuffer.new("Hello world")
+    assert_same string, I18n.interpolate(string, :planet => 'mars')
+  end
 end
 
 class I18nMissingInterpolationCustomHandlerTest < I18n::TestCase