Never return stored content from content_for when a block is given

actionpack/lib/action_view/helpers/capture_helper.rb

@@ -134,9 +134,13 @@ def capture(*args)
       # WARNING: content_for is ignored in caches. So you shouldn't use it
       # for elements that will be fragment cached.
       def content_for(name, content = nil, &block)
-        content = capture(&block) if block_given?
-        @_content_for[name] << content if content
-        @_content_for[name] unless content
+        if content || block_given?
+          content = capture(&block) if block_given?
+          @_content_for[name] << content if content
+          nil
+        else
+          @_content_for[name]
+        end
       end
 
       # content_for? simply checks whether any content has been captured yet using content_for

actionpack/test/template/capture_helper_test.rb

@@ -47,6 +47,31 @@ def test_content_for
     assert ! content_for?(:something_else)
   end
 
+  def test_content_for_with_multiple_calls
+    assert ! content_for?(:title)
+    content_for :title, 'foo'
+    content_for :title, 'bar'
+    assert_equal 'foobar', content_for(:title)
+  end
+
+  def test_content_for_with_block
+    assert ! content_for?(:title)
+    content_for :title do
+      output_buffer << 'foo'
+      output_buffer << 'bar'
+      nil
+    end
+    assert_equal 'foobar', content_for(:title)
+  end
+
+  def test_content_for_returns_nil_when_writing
+    assert ! content_for?(:title)
+    assert_equal nil, content_for(:title, 'foo')
+    assert_equal nil, content_for(:title) { output_buffer << 'bar'; nil }
+    assert_equal nil, content_for(:title) { output_buffer << "  \n  "; nil }
+    assert_equal 'foobar', content_for(:title)
+  end
+
   def test_with_output_buffer_swaps_the_output_buffer_given_no_argument
     assert_nil @av.output_buffer
     buffer = @av.with_output_buffer do