Sever infinite loop for mutual dependencies. Closes #2997.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3181 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/lib/active_support/dependencies.rb

@@ -45,18 +45,26 @@ def require_or_load(file_name)
       # Append .rb if we have a bare file name.
       load_file_name = (file_name =~ /\.rb$/ ? file_name : "#{file_name}.rb")
 
+      # Record that we've seen this file *before* loading it to avoid an
+      # infinite loop with mutual dependencies.
+      loaded << file_name
+
+      begin
         # Enable warnings iff this file has not been loaded before.
         if history.include?(file_name)
           load load_file_name
         else
           enable_warnings { load load_file_name }
         end
+      rescue
+        loaded.delete file_name
+        raise
+      end
     else
       require file_name
     end
 
-    # Record that we've seen this file.
-    loaded  << file_name
+    # Record history *after* loading so first load gets warnings.
     history << file_name
   end
 

activesupport/test/dependencies/mutual_one.rb

@@ -0,0 +1,2 @@
+$mutual_dependencies_count += 1
+require_dependency 'mutual_two'

activesupport/test/dependencies/mutual_two.rb

@@ -0,0 +1,2 @@
+$mutual_dependencies_count += 1
+require_dependency 'mutual_one'

activesupport/test/dependencies/raises_exception.rb

@@ -1,2 +1,3 @@
 $raises_exception_load_count += 1
 raise 'Loading me failed, so do not add to loaded or history.'
+$raises_exception_load_count += 1

activesupport/test/dependencies_test.rb

@@ -79,4 +79,22 @@ def test_warnings_should_be_enabled_on_first_load
   ensure
     Dependencies.mechanism = old_mechanism
   end
+
+  def test_mutual_dependencies_dont_infinite_loop
+    $LOAD_PATH.unshift "#{File.dirname(__FILE__)}/dependencies"
+    old_mechanism, Dependencies.mechanism = Dependencies.mechanism, :load
+
+    $mutual_dependencies_count = 0
+    assert_nothing_raised { require_dependency 'mutual_one' }
+    assert_equal 2, $mutual_dependencies_count
+
+    Dependencies.clear
+
+    $mutual_dependencies_count = 0
+    assert_nothing_raised { require_dependency 'mutual_two' }
+    assert_equal 2, $mutual_dependencies_count
+  ensure
+    $LOAD_PATH.shift
+    Dependencies.mechanism = old_mechanism
+  end
 end