From 991ce7dbc68db3039cf2905a295d7aa823e4467c Mon Sep 17 00:00:00 2001
From: Nick Sieger <nick@nicksieger.com>
Date: Tue, 30 Sep 2008 12:08:33 -0500
Subject: [PATCH] [#1144]: Provide alternate implementation of Object#subclasses_of for JRuby

---
 .../active_support/core_ext/object/extending.rb    |   43 +++++++++++++++-----
 1 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/activesupport/lib/active_support/core_ext/object/extending.rb b/activesupport/lib/active_support/core_ext/object/extending.rb
index 082e98a..bbf6f85 100644
--- a/activesupport/lib/active_support/core_ext/object/extending.rb
+++ b/activesupport/lib/active_support/core_ext/object/extending.rb
@@ -3,22 +3,43 @@ class Object
     Class.remove_class(*subclasses_of(*superclasses))
   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 subclasses_of(*superclasses) #:nodoc:
-    subclasses = []
-
-    superclasses.each do |sup|
-      ObjectSpace.each_object(class << sup; self; end) do |k|
-        if k != sup && (k.name.blank? || eval("defined?(::#{k}) && ::#{k}.object_id == k.object_id"))
-          subclasses << k
+  begin
+    ObjectSpace.each_object(Class.new) {}
+
+    # 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:
+      subclasses = []
+
+      superclasses.each do |sup|
+        ObjectSpace.each_object(class << sup; self; end) do |k|
+          if k != sup && (k.name.blank? || eval("defined?(::#{k}) && ::#{k}.object_id == k.object_id"))
+            subclasses << k
+          end
         end
       end
+
+      subclasses
     end
+  rescue RuntimeError
+    # JRuby and any implementations which cannot handle the objectspace traversal
+    # above fall back to this implementation
+    def subclasses_of(*superclasses) #:nodoc:
+      subclasses = []
 
-    subclasses
+      superclasses.each do |sup|
+        ObjectSpace.each_object(Class) do |k|
+          if superclasses.any? { |superclass| k < superclass } &&
+            (k.name.blank? || eval("defined?(::#{k}) && ::#{k}.object_id == k.object_id"))
+            subclasses << k
+          end
+        end
+        subclasses.uniq!
+      end
+      subclasses
+    end
   end
 
   def extended_by #:nodoc:
-- 
1.5.6