Fix safe buffer by adding a dirty status.

activesupport/lib/active_support/core_ext/string/output_safety.rb

@@ -76,10 +76,24 @@ end
 module ActiveSupport #:nodoc:
   class SafeBuffer < String
     UNSAFE_STRING_METHODS = ["capitalize", "chomp", "chop", "delete", "downcase", "gsub", "lstrip", "next", "reverse", "rstrip", "slice", "squeeze", "strip", "sub", "succ", "swapcase", "tr", "tr_s", "upcase"].freeze
+
+    # TODO: Should safe_concat check if the current buffer is dirty or not?
+    # We should probably raise as it would mean we are adding concatenating
+    # to something that is safe but it actually isn't.
     alias safe_concat concat
 
+    def initialize(*)
+      @dirty = false
+      super
+    end
+
+    def initialize_copy(other)
+      super
+      @dirty = other.dirty?
+    end
+
     def concat(value)
-      if value.html_safe?
+      if dirty? || value.html_safe?
         super(value)
       else
         super(ERB::Util.h(value))
@@ -92,11 +106,7 @@ module ActiveSupport #:nodoc:
     end
 
     def html_safe?
-      true
-    end
-
-    def html_safe
-      self
+      !dirty?
     end
 
     def to_s
@@ -113,7 +123,6 @@ module ActiveSupport #:nodoc:
 
     def to_yaml(*args)
       return super() if defined?(YAML::ENGINE) && !YAML::ENGINE.syck?
-
       to_str.to_yaml(*args)
     end
 
@@ -124,18 +133,21 @@ module ActiveSupport #:nodoc:
         end
 
         def #{unsafe_method}!(*args)
-          raise TypeError, "Cannot modify SafeBuffer in place"
+          @dirty = true
+          super
         end
       EOT
     end
+
+    protected
+
+    def dirty?
+      @dirty
+    end
   end
 end
 
 class String
-  def html_safe!
-    raise "You can't call html_safe! on a String"
-  end
-
   def html_safe
     ActiveSupport::SafeBuffer.new(self)
   end

activesupport/test/safe_buffer_test.rb

@@ -4,6 +4,7 @@ begin
 rescue LoadError
 end
 
+require 'active_support/core_ext/string/inflections'
 require 'yaml'
 
 class SafeBufferTest < ActiveSupport::TestCase
@@ -45,7 +46,7 @@ class SafeBufferTest < ActiveSupport::TestCase
     assert_equal ActiveSupport::SafeBuffer, new_buffer.class
   end
 
-  def test_to_yaml
+  test "Should be converted to_yaml" do
     str  = 'hello!'
     buf  = ActiveSupport::SafeBuffer.new str
     yaml = buf.to_yaml
@@ -54,22 +55,46 @@ class SafeBufferTest < ActiveSupport::TestCase
     assert_equal 'hello!', YAML.load(yaml)
   end
 
-  def test_nested
+  test "Should work in nested to_yaml conversion" do
     str  = 'hello!'
     data = { 'str' => ActiveSupport::SafeBuffer.new(str) }
     yaml = YAML.dump data
     assert_equal({'str' => str}, YAML.load(yaml))
   end
 
+  test "Should work with underscore" do
+    str = "MyTest".html_safe.underscore
+    assert_equal "my_test", str
+  end
+
   test "Should not return safe buffer from gsub" do
     altered_buffer = @buffer.gsub('', 'asdf')
     assert_equal 'asdf', altered_buffer
     assert !altered_buffer.html_safe?
   end
 
-  test "Should not allow gsub! on safe buffers" do
-    assert_raise TypeError do
+  test "Should not return safe buffer from gsub!" do
     @buffer.gsub!('', 'asdf')
-    end
+    assert_equal 'asdf', @buffer
+    assert !@buffer.html_safe?
+  end
+
+  test "Should escape dirty buffers on add" do
+    dirty = @buffer
+    clean = "hello".html_safe
+    @buffer.gsub!('', '<>')
+    assert_equal "hello&lt;&gt;", clean + @buffer
+  end
+
+  test "Should concat as a normal string when dirty" do
+    dirty = @buffer
+    clean = "hello".html_safe
+    @buffer.gsub!('', '<>')
+    assert_equal "<>hello", @buffer + clean
+  end
+
+  test "Should preserve dirty? status on copy" do
+    @buffer.gsub!('', '<>')
+    assert !@buffer.dup.html_safe?
   end
 end