6 files changed, 94 insertions, 7 deletions

diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index c166ce8079..bbd8f5aef6 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -1,4 +1,5 @@
-require 'active_support/core_ext/object/blank'
+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.
@@ -8,10 +9,6 @@ class Class #:nodoc:
     Class.subclasses_of(self).map { |o| o.to_s }
   end
 
-  def reachable? #:nodoc:
-    eval("defined?(::#{self}) && ::#{self}.equal?(self)")
-  end
-
   # Rubinius
   if defined?(Class.__subclasses__)
     def descendents
@@ -51,7 +48,7 @@ class Class #:nodoc:
   def self.subclasses_of(*superclasses) #:nodoc:
     subclasses = []
     superclasses.each do |klass|
-      subclasses.concat klass.descendents.select {|k| k.name.blank? || k.reachable?}
+      subclasses.concat klass.descendents.select {|k| k.anonymous? || k.reachable?}
     end
     subclasses
   end
diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb
index 41600929f4..07bac29a9f 100644
--- a/activesupport/lib/active_support/core_ext/module.rb
+++ b/activesupport/lib/active_support/core_ext/module.rb
@@ -1,6 +1,7 @@
 require 'active_support/core_ext/module/aliasing'
 require 'active_support/core_ext/module/introspection'
-
+require 'active_support/core_ext/module/anonymous'
+require 'active_support/core_ext/module/reachable'
 require 'active_support/core_ext/module/attribute_accessors'
 require 'active_support/core_ext/module/attr_internal'
 require 'active_support/core_ext/module/attr_accessor_with_default'
diff --git a/activesupport/lib/active_support/core_ext/module/anonymous.rb b/activesupport/lib/active_support/core_ext/module/anonymous.rb
new file mode 100644
index 0000000000..df25a09ec9
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/anonymous.rb
@@ -0,0 +1,24 @@
+require 'active_support/core_ext/object/blank'
+
+class Module
+  # A module may or may not have a name.
+  #
+  #   module M; end
+  #   M.name # => "M"
+  #
+  #   m = Module.new
+  #   m.name # => ""
+  #
+  # A module gets a name when it is first assigned to a constant. Either
+  # via the +module+ or +class+ keyword or by an explicit assignment:
+  #
+  #   m = Module.new # creates an anonymous module
+  #   M = m          # => m gets a name here as a side-effect
+  #   m.name         # => "M"
+  #
+  def anonymous?
+    # Uses blank? because the name of an anonymous class is an empty
+    # string in 1.8, and nil in 1.9.
+    name.blank? 
+  end
+end
diff --git a/activesupport/lib/active_support/core_ext/module/reachable.rb b/activesupport/lib/active_support/core_ext/module/reachable.rb
new file mode 100644
index 0000000000..443d2c3d53
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/reachable.rb
@@ -0,0 +1,10 @@
+require 'active_support/core_ext/module/anonymous'
+require 'active_support/core_ext/string/inflections'
+
+class Module
+  def reachable? #:nodoc:
+    !anonymous? && name.constantize.equal?(self)
+  rescue NameError
+    false
+  end
+end
diff --git a/activesupport/test/core_ext/module/anonymous_test.rb b/activesupport/test/core_ext/module/anonymous_test.rb
new file mode 100644
index 0000000000..7a78a3b012
--- /dev/null
+++ b/activesupport/test/core_ext/module/anonymous_test.rb
@@ -0,0 +1,14 @@
+require 'abstract_unit'
+require 'active_support/core_ext/module/anonymous'
+
+class AnonymousTest < ActiveSupport::TestCase
+  test "an anonymous class or module are anonymous" do
+    assert Module.new.anonymous?
+    assert Class.new.anonymous?
+  end
+  
+  test "a named class or module are not anonymous" do
+    assert !Kernel.anonymous?
+    assert !Object.anonymous?
+  end
+end
\ No newline at end of file
diff --git a/activesupport/test/core_ext/module/reachable_test.rb b/activesupport/test/core_ext/module/reachable_test.rb
new file mode 100644
index 0000000000..72892b77d5
--- /dev/null
+++ b/activesupport/test/core_ext/module/reachable_test.rb
@@ -0,0 +1,41 @@
+require 'abstract_unit'
+require 'active_support/core_ext/module/reachable'
+
+class AnonymousTest < ActiveSupport::TestCase
+  test "an anonymous class or module is not reachable" do
+    assert !Module.new.reachable?
+    assert !Class.new.reachable?
+  end
+  
+  test "ordinary named classes or modules are reachable" do
+    assert Kernel.reachable?
+    assert Object.reachable?
+  end
+  
+  test "a named class or module whose constant has gone is not reachable" do
+    c = eval "class C; end; C"
+    m = eval "module M; end; M"
+    
+    self.class.send(:remove_const, :C)
+    self.class.send(:remove_const, :M)
+    
+    assert !c.reachable?
+    assert !m.reachable?
+  end
+  
+  test "a named class or module whose constants store different objects are not reachable" do
+    c = eval "class C; end; C"
+    m = eval "module M; end; M"
+    
+    self.class.send(:remove_const, :C)
+    self.class.send(:remove_const, :M)    
+
+    eval "class C; end"
+    eval "module M; end"
+    
+    assert C.reachable?
+    assert M.reachable?
+    assert !c.reachable?
+    assert !m.reachable?
+  end
+end
\ No newline at end of file