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, 19 insertions, 21 deletions

diff --git a/activesupport/test/core_ext/class_test.rb b/activesupport/test/core_ext/class_test.rb
index b7f3dd9930..08bb13dd35 100644
--- a/activesupport/test/core_ext/class_test.rb
+++ b/activesupport/test/core_ext/class_test.rb
@@ -1,29 +1,27 @@
 require 'abstract_unit'
 require 'active_support/core_ext/class'
 
-class A
-end
+class ClassTest < Test::Unit::TestCase
+  class Parent; end
+  class Foo < Parent; end
+  class Bar < Foo; end
+  class Baz < Bar; end
 
-module X
-  class B
-  end
-end
+  class A < Parent; end
+  class B < A; end
+  class C < B; end
 
-module Y
-  module Z
-    class C
-    end
+  def test_descendants
+    assert_equal [Foo, Bar, Baz, A, B, C], Parent.descendants
+    assert_equal [Bar, Baz], Foo.descendants
+    assert_equal [Baz], Bar.descendants
+    assert_equal [], Baz.descendants
   end
-end
 
-class ClassTest < Test::Unit::TestCase
-  def test_retrieving_subclasses
-    @parent   = eval("class D; end; D")
-    @sub      = eval("class E < D; end; E")
-    @subofsub = eval("class F < E; end; F")
-    assert_equal 2, @parent.subclasses.size
-    assert_equal [@subofsub.to_s], @sub.subclasses
-    assert_equal [], @subofsub.subclasses
-    assert_equal [@sub.to_s, @subofsub.to_s].sort, @parent.subclasses.sort
+  def test_subclasses
+    assert_equal [Foo, A], Parent.subclasses
+    assert_equal [Bar], Foo.subclasses
+    assert_equal [Baz], Bar.subclasses
+    assert_equal [], Baz.subclasses
   end
-end
+end
\ No newline at end of file