don't throw excpetion for delegate classes (generators)

lib/lumber/lumber.rb

@@ -139,12 +139,11 @@ def self.derive_lumber_logger(clazz)
     # logger of the new class
     parent = clazz.superclass
     while ! parent.nil?
-      if parent.method_defined?(:logger) && parent.method_defined?(:logger=) && parent.logger
-        parent_is_registered = @@registered_loggers.values.find {|v| parent.logger.fullname.index(v) == 0}
-        if parent_is_registered
-          clazz.logger = Log4r::Logger.new("#{parent.logger.fullname}::#{clazz.name}")
-          break
-        end
+      parent_logger_name = parent.logger.fullname rescue ''
+      parent_is_registered = @@registered_loggers.values.find {|v| parent_logger_name.index(v) == 0}
+      if parent_is_registered && parent.method_defined?(:logger=)
+        clazz.logger = Log4r::Logger.new("#{parent_logger_name}::#{clazz.name}")
+        break
       end
       parent = parent.superclass
     end

test/lumber_test.rb

@@ -1,5 +1,5 @@
 require 'test_helper'
-
+require 'delegate'
 
 def new_class(class_name, super_class=nil, super_module=nil)
   s = "class #{class_name}"
@@ -61,6 +61,18 @@ def assert_valid_logger(class_name, logger_name)
     assert Foo3.new.logger == Foo1.logger
   end
 
+  should "no logger when parent is via delegate class" do
+    assert !defined?(Foo1)
+    assert !defined?(Foo2)
+    assert !defined?(Foo3)
+    Lumber.setup_logger_hierarchy("Foo1", "root::foo1")
+    eval "class ::Foo1; end"
+    eval "class ::Foo2 < DelegateClass(Foo1); end"
+    eval "class ::Foo3 < Foo2; end"
+    assert_valid_logger('Foo1', "root::foo1")
+    assert ! defined?(Foo3.logger)
+  end
+
   should "allow registering independent loggers for classes in a hierarchy" do
     assert !defined?(Foo1)
     assert !defined?(Foo2)