Stop using defined? in Dependencies.qualified_const_defined? since defined?...

Stop using defined? in Dependencies.qualified_const_defined? since defined? may invoke const_missing.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4774 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/CHANGELOG

 *SVN*
 
+* Stop using defined? in Dependencies.qualified_const_defined? since defined? may invoke const_missing. [Nicholas Seckar]
+
 * Dependencies can autoload directories of nested classes. [Jeremy Kemper]
     Example:
       invoice.rb            class Invoice

activesupport/lib/active_support/dependencies.rb

@@ -96,7 +96,17 @@ def require_or_load(file_name, const_path = nil)
   def qualified_const_defined?(path)
     raise NameError, "#{path.inspect} is not a valid constant name!" unless
       /^(::)?([A-Z]\w*)(::[A-Z]\w*)*$/ =~ path
-    Object.module_eval("defined?(#{path})", __FILE__, __LINE__)
+    
+    names = path.split('::')
+    names.shift if names.first.empty?
+    
+    # We can't use defined? because it will invoke const_missing for the parent
+    # of the name we are checking.
+    names.inject(Object) do |mod, name|
+      return false unless mod.const_defined? name
+      mod.const_get name
+    end
+    return true
   end
   
   # Given +path+ return an array of constant paths which would cause Dependencies

activesupport/test/dependencies_test.rb

 require File.dirname(__FILE__) + '/abstract_unit'
 
+module ModuleWithMissing
+  mattr_accessor :missing_count
+  def self.const_missing(name)
+    self.missing_count += 1
+    name
+  end
+end
+
 class DependenciesTest < Test::Unit::TestCase
   
   def teardown
@@ -249,6 +257,14 @@ def test_qualified_const_defined
     assert Dependencies.qualified_const_defined?("::Test::Unit::TestCase")
   end
   
+  def test_qualified_const_defined_should_not_call_method_missing
+    ModuleWithMissing.missing_count = 0
+    assert ! Dependencies.qualified_const_defined?("ModuleWithMissing::A")
+    assert_equal 0, ModuleWithMissing.missing_count
+    assert ! Dependencies.qualified_const_defined?("ModuleWithMissing::A::B")
+    assert_equal 0, ModuleWithMissing.missing_count
+  end
+  
   def test_autoloaded?
     with_loading 'autoloading_fixtures' do
       assert ! Dependencies.autoloaded?("ModuleFolder")