sub, sub!, gsub, and gsub! should set back references

2 files changed, 62 insertions, 2 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 3a80de4617..e3f62d7d26 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -135,10 +135,12 @@ module ActiveSupport #:nodoc:
   class SafeBuffer < String
     UNSAFE_STRING_METHODS = %w(
       capitalize chomp chop delete delete_prefix delete_suffix
-      downcase gsub lstrip next reverse rstrip slice squeeze strip
-      sub succ swapcase tr tr_s unicode_normalize upcase
+      downcase lstrip next reverse rstrip slice squeeze strip
+      succ swapcase tr tr_s unicode_normalize upcase
     )
 
+    UNSAFE_STRING_METHODS_WITH_BACKREF = %w(gsub sub)
+
     alias_method :original_concat, :concat
     private :original_concat
 
@@ -249,11 +251,51 @@ module ActiveSupport #:nodoc:
       end
     end
 
+    UNSAFE_STRING_METHODS_WITH_BACKREF.each do |unsafe_method|
+      if unsafe_method.respond_to?(unsafe_method)
+        class_eval <<-EOT, __FILE__, __LINE__ + 1
+          def #{unsafe_method}(*args, &block)
+            if block
+              to_str.#{unsafe_method}(*args) { |*params|
+                set_block_back_references(block, $~)
+                block.call(*params)
+              }
+            else
+              to_str.#{unsafe_method}(*args)
+            end
+          end
+
+          def #{unsafe_method}!(*args, &block)
+            @html_safe = false
+            if block
+              super(*args) { |*params|
+                set_block_back_references(block, $~)
+                block.call(*params)
+              }
+            else
+              super
+            end
+          end
+        EOT
+      end
+    end
+
     private
 
       def html_escape_interpolated_argument(arg)
         (!html_safe? || arg.html_safe?) ? arg : CGI.escapeHTML(arg.to_s)
       end
+
+      def set_block_back_references(block, match_data)
+        Thread.current[:__active_support_safe_buffer_backref] = match_data
+        begin
+          block.binding.eval(<<-EOC)
+            $~ = Thread.current[:__active_support_safe_buffer_backref]
+          EOC
+        ensure
+          Thread.current[:__active_support_safe_buffer_backref] = nil
+        end
+      end
   end
 end
 
diff --git a/activesupport/test/safe_buffer_test.rb b/activesupport/test/safe_buffer_test.rb
index 49a3951623..9449adb6de 100644
--- a/activesupport/test/safe_buffer_test.rb
+++ b/activesupport/test/safe_buffer_test.rb
@@ -216,4 +216,22 @@ class SafeBufferTest < ActiveSupport::TestCase
     x = "Hello".html_safe
     assert_nil x[/a/, 1]
   end
+
+  test "Should set back references" do
+    a = "foo123".html_safe
+    a2 = a.sub(/([a-z]+)([0-9]+)/) { $2 + $1 }
+    assert_equal "123foo", a2
+    assert_not_predicate a2, :html_safe?
+    a.sub!(/([a-z]+)([0-9]+)/) { $2 + $1 }
+    assert_equal "123foo", a
+    assert_not_predicate a, :html_safe?
+
+    b = "foo123 bar456".html_safe
+    b2 = b.gsub(/([a-z]+)([0-9]+)/) { $2 + $1 }
+    assert_equal "123foo 456bar", b2
+    assert_not_predicate b2, :html_safe?
+    b.gsub!(/([a-z]+)([0-9]+)/) { $2 + $1 }
+    assert_equal "123foo 456bar", b
+    assert_not_predicate b, :html_safe?
+  end
 end