5 files changed, 44 insertions, 11 deletions
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index b86e988841..d643a08235 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1 +1,12 @@
+*   Change the way in which callback chains can be halted.
+
+    The preferred method to halt a callback chain from now on is to explicitly
+    `throw(:abort)`.
+    In the past, returning `false` in an ActiveModel or ActiveModel::Validations
+    `before_` callback had the side effect of halting the callback chain.
+    This is not recommended anymore and, depending on the value of the
+    `config.active_support.halt_callback_chains_on_return_false` option, will
+    either not work at all or display a deprecation warning.
+
+
 Please check [4-2-stable](https://github.com/rails/rails/blob/4-2-stable/activemodel/CHANGELOG.md) for previous changes.
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
diff --git a/activemodel/test/cases/callbacks_test.rb b/activemodel/test/cases/callbacks_test.rb
index 2ac681b8d8..85455c112c 100644
--- a/activemodel/test/cases/callbacks_test.rb
+++ b/activemodel/test/cases/callbacks_test.rb
@@ -33,11 +33,13 @@ class CallbacksTest < ActiveModel::TestCase
     def initialize(options = {})
       @callbacks = []
       @valid = options[:valid]
-      @before_create_returns = options[:before_create_returns]
+      @before_create_returns = options.fetch(:before_create_returns, true)
+      @before_create_throws = options[:before_create_throws]
     end
 
     def before_create
       @callbacks << :before_create
+      throw(@before_create_throws) if @before_create_throws
       @before_create_returns
     end
 
@@ -62,10 +64,18 @@ class CallbacksTest < ActiveModel::TestCase
     assert_equal model.callbacks.last, :final_callback
   end
 
-  test "the callback chain is halted when a before callback returns false" do
+  test "the callback chain is halted when a before callback returns false (deprecated)" do
     model = ModelCallbacks.new(before_create_returns: false)
+    assert_deprecated do
+      model.create
+      assert_equal model.callbacks.last, :before_create
+    end
+  end
+
+  test "the callback chain is halted when a callback throws :abort" do
+    model = ModelCallbacks.new(before_create_throws: :abort)
     model.create
-    assert_equal model.callbacks.last, :before_create
+    assert_equal model.callbacks, [:before_create]
   end
 
   test "after callbacks are not executed if the block returns false" do
diff --git a/activemodel/test/cases/validations/callbacks_test.rb b/activemodel/test/cases/validations/callbacks_test.rb
index 5d6d48b824..4b0dd58efb 100644
--- a/activemodel/test/cases/validations/callbacks_test.rb
+++ b/activemodel/test/cases/validations/callbacks_test.rb
@@ -30,11 +30,16 @@ class DogWithTwoValidators < Dog
   before_validation { self.history << 'before_validation_marker2' }
 end
 
-class DogBeforeValidatorReturningFalse < Dog
+class DogDeprecatedBeforeValidatorReturningFalse < Dog
   before_validation { false }
   before_validation { self.history << 'before_validation_marker2' }
 end
 
+class DogBeforeValidatorThrowingAbort < Dog
+  before_validation { throw :abort }
+  before_validation { self.history << 'before_validation_marker2' }
+end
+
 class DogAfterValidatorReturningFalse < Dog
   after_validation { false }
   after_validation { self.history << 'after_validation_marker' }
@@ -86,13 +91,22 @@ class CallbacksWithMethodNamesShouldBeCalled < ActiveModel::TestCase
     assert_equal ['before_validation_marker1', 'before_validation_marker2'], d.history
   end
 
-  def test_further_callbacks_should_not_be_called_if_before_validation_returns_false
-    d = DogBeforeValidatorReturningFalse.new
+  def test_further_callbacks_should_not_be_called_if_before_validation_throws_abort
+    d = DogBeforeValidatorThrowingAbort.new
     output = d.valid?
     assert_equal [], d.history
     assert_equal false, output
   end
 
+  def test_deprecated_further_callbacks_should_not_be_called_if_before_validation_returns_false
+    d = DogDeprecatedBeforeValidatorReturningFalse.new
+    assert_deprecated do
+      output = d.valid?
+      assert_equal [], d.history
+      assert_equal false, output
+    end
+  end
+
   def test_further_callbacks_should_be_called_if_after_validation_returns_false
     d = DogAfterValidatorReturningFalse.new
     d.valid?