Merge pull request #17227 from claudiob/explicitly-abort-callbacks

Introduce explicit way of halting callback chains by throwing :abort. Deprecate current implicit behavior of halting callback chains by returning `false` in apps ported to Rails 5.0. Completely remove that behavior in brand new Rails 5.0 apps.

Conflicts:
	railties/CHANGELOG.md

2 files changed, 3 insertions, 5 deletions

diff --git a/activemodel/lib/active_model/callbacks.rb b/activemodel/lib/active_model/callbacks.rb
index b3d70dc515..6214802074 100644
--- a/activemodel/lib/active_model/callbacks.rb
+++ b/activemodel/lib/active_model/callbacks.rb
@@ -6,7 +6,7 @@ module ActiveModel
   # Provides an interface for any class to have Active Record like callbacks.
   #
   # Like the Active Record methods, the callback chain is aborted as soon as
-  # one of the methods in the chain returns +false+.
+  # one of the methods throws +:abort+.
   #
   # First, extend ActiveModel::Callbacks from the class you are creating:
   #
@@ -103,7 +103,6 @@ module ActiveModel
     def define_model_callbacks(*callbacks)
       options = callbacks.extract_options!
       options = {
-        terminator: ->(_,result) { result == false },
         skip_after_callbacks_if_terminated: true,
         scope: [:kind, :name],
         only: [:before, :around, :after]
diff --git a/activemodel/lib/active_model/validations/callbacks.rb b/activemodel/lib/active_model/validations/callbacks.rb
index 25ccabd66b..4b58ef66e3 100644
--- a/activemodel/lib/active_model/validations/callbacks.rb
+++ b/activemodel/lib/active_model/validations/callbacks.rb
@@ -15,15 +15,14 @@ module ActiveModel
     #     after_validation  :do_stuff_after_validation
     #   end
     #
-    # Like other <tt>before_*</tt> callbacks if +before_validation+ returns
-    # +false+ then <tt>valid?</tt> will not be called.
+    # Like other <tt>before_*</tt> callbacks if +before_validation+ throws
+    # +:abort+ then <tt>valid?</tt> will not be called.
     module Callbacks
       extend ActiveSupport::Concern
 
       included do
         include ActiveSupport::Callbacks
         define_callbacks :validation,
-                         terminator: ->(_,result) { result == false },
                          skip_after_callbacks_if_terminated: true,
                          scope: [:kind, :name]
       end