Log 'Filter chain halted as CALLBACKNAME rendered or redirected' every time a before callback halts.

2 files changed, 25 insertions, 5 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index ea37355fc1..11069301f1 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -81,6 +81,14 @@ module ActiveSupport
       send("_run_#{kind}_callbacks", *args, &block)
     end
 
+    private
+
+    # A hook invoked everytime a before callback is halted.
+    # This can be overriden in AS::Callback implementors in order
+    # to provide better debugging/logging.
+    def halted_callback_hook(filter)
+    end
+
     class Callback #:nodoc:#
       @@_callback_sequence = 0
 
@@ -173,12 +181,14 @@ module ActiveSupport
           # end
           <<-RUBY_EVAL
             if !halted && #{@compiled_options}
-              # This double assignment is to prevent warnings in 1.9.3.  I would
-              # remove the `result` variable, but apparently some other
-              # generated code is depending on this variable being set sometimes
-              # and sometimes not.
+              # This double assignment is to prevent warnings in 1.9.3 as
+              # the `result` variable is not always used except if the
+              # terminator code refers to it.
               result = result = #{@filter}
               halted = (#{chain.config[:terminator]})
+              if halted
+                halted_callback_hook(#{@raw_filter.inspect.inspect})
+              end
             end
           RUBY_EVAL
         when :around
diff --git a/activesupport/test/callbacks_test.rb b/activesupport/test/callbacks_test.rb
index 2b4adda4d1..e723121bb4 100644
--- a/activesupport/test/callbacks_test.rb
+++ b/activesupport/test/callbacks_test.rb
@@ -461,7 +461,7 @@ module CallbacksTest
     set_callback :save, :after, :third
 
 
-    attr_reader :history, :saved
+    attr_reader :history, :saved, :halted
     def initialize
       @history = []
     end
@@ -490,6 +490,10 @@ module CallbacksTest
         @saved = true
       end
     end
+
+    def halted_callback_hook(filter)
+      @halted = filter
+    end
   end
 
   class CallbackObject
@@ -595,6 +599,12 @@ module CallbacksTest
       assert_equal ["first", "second", "third", "second", "first"], terminator.history
     end
 
+    def test_termination_invokes_hook
+      terminator = CallbackTerminator.new
+      terminator.save
+      assert_equal ":second", terminator.halted
+    end
+
     def test_block_never_called_if_terminated
       obj = CallbackTerminator.new
       obj.save