2 files changed, 75 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 c930abc003..0c8fc20ea5 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -122,3 +122,34 @@ class String
     ActiveSupport::SafeBuffer.new(self)
   end
 end
+
+class Array
+  # If the separator and all the items in the array are html safe
+  # then an html safe string is returned using <tt>Array#join</tt>,
+  # otherwise the result of <tt>Array#join</tt> is returned without
+  # marking it as html safe.
+  #
+  #   ["Mr", "Bojangles"].join.html_safe?
+  #   # => false
+  #
+  #   ["Mr".html_safe, "Bojangles".html_safe].join.html_safe?
+  #   # => true
+  #
+  def safe_join(sep=$,)
+    sep ||= "".html_safe
+    str = join(sep)
+    (sep.html_safe? && html_safe?) ? str.html_safe : str
+  end
+
+  # Returns +true+ if all items in the array are html safe.
+  #
+  #   [""].html_safe?
+  #   # => false
+  #
+  #   ["".html_safe].html_safe?
+  #   # => true
+  #
+  def html_safe?
+    detect { |e| !e.html_safe? }.nil?
+  end
+end
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index bb865cae91..15e39a06c3 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -434,6 +434,50 @@ class OutputSafetyTest < ActiveSupport::TestCase
     assert string.html_safe?
   end
 
+  test "Joining safe elements without a separator is safe" do
+    array = 5.times.collect { "some string".html_safe }
+    assert array.safe_join.html_safe?
+  end
+
+  test "Joining safe elements with a safe separator is safe" do
+    array = 5.times.collect { "some string".html_safe }
+    assert array.safe_join("-".html_safe).html_safe?
+  end
+
+  test "Joining safe elements with an unsafe separator is unsafe" do
+    array = 5.times.collect { "some string".html_safe }
+    assert !array.safe_join("-").html_safe?
+  end
+
+  test "Joining is unsafe if any element is unsafe even with a safe separator" do
+    array = 5.times.collect { "some string".html_safe }
+    array << "some string"
+    assert !array.safe_join("-".html_safe).html_safe?
+  end
+
+  test "Joining is unsafe if any element is unsafe and no separator is given" do
+    array = 5.times.collect { "some string".html_safe }
+    array << "some string"
+    assert !array.safe_join.html_safe?
+  end
+
+  test "Joining is unsafe if any element is unsafe and the separator is unsafe" do
+    array = 5.times.collect { "some string".html_safe }
+    array << "some string"
+    assert !array.safe_join("-").html_safe?
+  end
+
+  test "Array is safe if all elements are safe" do
+    array = 5.times.collect { "some string".html_safe }
+    assert array.html_safe?
+  end
+
+  test "Array is unsafe if any element is unsafe" do
+    array = 5.times.collect { "some string".html_safe }
+    array << "some string"
+    assert !array.html_safe?
+  end
+
   test 'emits normal string yaml' do
     assert_equal 'foo'.to_yaml, 'foo'.html_safe.to_yaml(:foo => 1)
   end