add AS::SafeBuffer#clone_empty

2 files changed, 15 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index c6d861d124..5b39fd6a6a 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -119,6 +119,12 @@ module ActiveSupport #:nodoc:
       @dirty = other.dirty?
     end
 
+    def clone_empty
+      new_safe_buffer = self[0, 0]
+      new_safe_buffer.instance_variable_set(:@dirty, @dirty)
+      new_safe_buffer
+    end
+
     def concat(value)
       if dirty? || value.html_safe?
         super(value)
diff --git a/activesupport/test/safe_buffer_test.rb b/activesupport/test/safe_buffer_test.rb
index db9159b289..20731218cf 100644
--- a/activesupport/test/safe_buffer_test.rb
+++ b/activesupport/test/safe_buffer_test.rb
@@ -116,4 +116,13 @@ class SafeBufferTest < ActiveSupport::TestCase
     assert_not_nil dirty
     assert !dirty
   end
+
+  test "clone_empty returns an empty buffer" do
+    assert_equal '', ActiveSupport::SafeBuffer.new('foo').clone_empty
+  end
+
+  test "clone_empty keeps the original dirtyness" do
+    assert @buffer.clone_empty.html_safe?
+    assert !@buffer.gsub!('', '').clone_empty.html_safe?
+  end
 end