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.

5 files changed, 42 insertions, 55 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)
diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index 7d58a8b56a..3e5d1a2a42 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -2,54 +2,49 @@ require 'active_support/core_ext/module/anonymous'
 require 'active_support/core_ext/module/reachable'
 
 class Class #:nodoc:
-  # Returns an array with the names of the subclasses of +self+ as strings.
-  #
-  #   Integer.subclasses # => ["Bignum", "Fixnum"]
-  def subclasses
-    Class.subclasses_of(self).map { |o| o.to_s }
-  end
-
   # Rubinius
   if defined?(Class.__subclasses__)
+    alias :subclasses :__subclasses__
+
     def descendants
-      subclasses = []
-      __subclasses__.each {|k| subclasses << k; subclasses.concat k.descendants }
-      subclasses
+      descendants = []
+      __subclasses__.each do |k|
+        descendants << k
+        descendants.concat k.descendants
+      end
+      descendants
     end
-  else
-    # MRI
+  else # MRI
     begin
       ObjectSpace.each_object(Class.new) {}
 
       def descendants
-        subclasses = []
+        descendants = []
         ObjectSpace.each_object(class << self; self; end) do |k|
-          subclasses << k unless k == self
+          descendants.unshift k unless k == self
         end
-        subclasses
+        descendants
       end
-    # JRuby
-    rescue StandardError
+    rescue StandardError # JRuby
       def descendants
-        subclasses = []
+        descendants = []
         ObjectSpace.each_object(Class) do |k|
-          subclasses << k if k < self
+          descendants.unshift k if k < self
         end
-        subclasses.uniq!
-        subclasses
+        descendants.uniq!
+        descendants
       end
     end
-  end
 
-  # Exclude this class unless it's a subclass of our supers and is defined.
-  # We check defined? in case we find a removed class that has yet to be
-  # garbage collected. This also fails for anonymous classes -- please
-  # submit a patch if you have a workaround.
-  def self.subclasses_of(*superclasses) #:nodoc:
-    subclasses = []
-    superclasses.each do |klass|
-      subclasses.concat klass.descendants.select {|k| k.anonymous? || k.reachable?}
+    # Returns an array with the direct children of +self+.
+    #
+    #   Integer.subclasses # => [Bignum, Fixnum]
+    def subclasses
+      subclasses, chain = [], descendants
+      chain.each do |k|
+        subclasses << k unless chain.any? { |c| c > k }
+      end
+      subclasses
     end
-    subclasses
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index 8922016cd7..27618b55c6 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -6,7 +6,6 @@ require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/instance_variables'
 require 'active_support/core_ext/object/misc'
-require 'active_support/core_ext/object/extending'
 
 require 'active_support/core_ext/object/returning'
 require 'active_support/core_ext/object/to_json'
diff --git a/activesupport/lib/active_support/core_ext/object/extending.rb b/activesupport/lib/active_support/core_ext/object/extending.rb
deleted file mode 100644
index c4c37b6a2a..0000000000
--- a/activesupport/lib/active_support/core_ext/object/extending.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require 'active_support/core_ext/class/subclasses'
-
-class Object
-  # Exclude this class unless it's a subclass of our supers and is defined.
-  # We check defined? in case we find a removed class that has yet to be
-  # garbage collected. This also fails for anonymous classes -- please
-  # submit a patch if you have a workaround.
-  def subclasses_of(*superclasses) #:nodoc:
-    Class.subclasses_of(*superclasses)
-  end
-end
diff --git a/activesupport/lib/active_support/descendants_tracker.rb b/activesupport/lib/active_support/descendants_tracker.rb
index a587d7770c..6cba84d79e 100644
--- a/activesupport/lib/active_support/descendants_tracker.rb
+++ b/activesupport/lib/active_support/descendants_tracker.rb
@@ -4,16 +4,23 @@ module ActiveSupport
   # This module provides an internal implementation to track descendants
   # which is faster than iterating through ObjectSpace.
   module DescendantsTracker
-    @@descendants = Hash.new { |h, k| h[k] = [] }
+    @@direct_descendants = Hash.new { |h, k| h[k] = [] }
 
-    def self.descendants
-      @@descendants
+    def self.direct_descendants(klass)
+      @@direct_descendants[klass]
+    end
+
+    def self.descendants(klass)
+      @@direct_descendants[klass].inject([]) do |descendants, klass|
+        descendants << klass
+        descendants.concat klass.descendants
+      end
     end
 
     def self.clear
-      @@descendants.each do |klass, descendants|
+      @@direct_descendants.each do |klass, descendants|
         if ActiveSupport::Dependencies.autoloaded?(klass)
-          @@descendants.delete(klass)
+          @@direct_descendants.delete(klass)
         else
           descendants.reject! { |v| ActiveSupport::Dependencies.autoloaded?(v) }
         end
@@ -26,14 +33,11 @@ module ActiveSupport
     end
 
     def direct_descendants
-      @@descendants[self]
+      DescendantsTracker.direct_descendants(self)
     end
 
     def descendants
-      @@descendants[self].inject([]) do |descendants, klass|
-        descendants << klass
-        descendants.concat klass.descendants
-      end
+      DescendantsTracker.descendants(self)
     end
   end
 end
\ No newline at end of file