Revert "remove string based terminators for `ActiveSupport::Callbacks`."

This reverts commit d108672dada7ba97d3b3b56f0c6001cea621061e.

Conflicts:

	activesupport/CHANGELOG.md

2 files changed, 6 insertions, 4 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 87c850bcf0..8c07a034cc 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,7 +1,3 @@
-*   Remove deprecated string based terminators for `ActiveSupport::Callbacks`.
-
-    *Yves Senn*
-
 *   Remove deprecated `String#encoding_aware?` core extensions (`core_ext/string/encoding`).
 
     *Arun Agrawal*
diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index d2991a218b..5c738572a8 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -718,6 +718,12 @@ module ActiveSupport
       #   would call <tt>Audit#save</tt>.
       def define_callbacks(*names)
         options = names.extract_options!
+        if options.key?(:terminator) && String === options[:terminator]
+          ActiveSupport::Deprecation.warn "String based terminators are deprecated, please use a lambda"
+          value = options[:terminator]
+          line = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__
+          options[:terminator] = lambda { |target, result| target.instance_exec(result, &line) }
+        end
 
         names.each do |name|
           class_attribute "_#{name}_callbacks"