Define a convention for descendants and subclasses.

The former should be symmetric with ancestors and include all children. However, it should not include self since ancestors + descendants should not have duplicated. The latter is symmetric to superclass in the sense it only includes direct children.

By adopting a convention, we expect to have less conflict with other frameworks, as Datamapper. For this moment, to ensure ActiveModel::Validations can be used with Datamapper, we should always call ActiveSupport::DescendantsTracker.descendants(self) internally instead of self.descendants avoiding conflicts.

1 files changed, 2 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index c4e1eb2c04..1c7802f7de 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -432,7 +432,7 @@ module ActiveSupport
         options = filters.last.is_a?(Hash) ? filters.pop : {}
         filters.unshift(block) if block
 
-        ([self] + self.descendants).each do |target|
+        ([self] + ActiveSupport::DescendantsTracker.descendants(self)).each do |target|
           chain = target.send("_#{name}_callbacks")
           yield chain, type, filters, options
           target.__define_runner(name)
@@ -506,7 +506,7 @@ module ActiveSupport
       def reset_callbacks(symbol)
         callbacks = send("_#{symbol}_callbacks")
 
-        self.descendants.each do |target|
+        ActiveSupport::DescendantsTracker.descendants(self).each do |target|
           chain = target.send("_#{symbol}_callbacks")
           callbacks.each { |c| chain.delete(c) }
           target.__define_runner(symbol)