'require' in lib code not evaluated twice in development mode?

I have a model that does an 'include' of a module defined in the lib
directory. The module, in turn, uses 'require' to load a class defined
in the system load path. Running the application in development mode,
the initial request goes through successfully. However, the second
time around, I get a NameError resulting from "uninitialized
constant", with the constant in question being a class that is defined
in the script that is 'require'd in the lib module. In brief it looks
like this:

app/model/revision.rb:
class Revision
   include MyLib::Mod
end

lib/my_lib/mod.rb:
module MyLib
  module Mod
    require 'extension/clazz'
  end
end

On the second request, the class defined in extension/clazz cannot be
found, resulting in the NameError. However, if I add "require
'extension/clazz'" into the model, just before the 'include', it works
such that every request is successful. Likewise, if I run the
applicaiton in production mode, it works every time.

Is this expected behavior, or is this a bug in Rails?

Thanks

n

Being new to Rails, it's no surprise I didn't understand what was
happening. So the scripts in the lib directory are only evaluated
once. While I knew that, I kinda forgot when faced with this problem.
Given that in development mode Rails will de-initialize all the
constants defined during the request (or something of that nature,
again I'm new to Rails), it threw away the classes that were defined
within the scripts in the lib directory. And given it never evaluated
those scripts again, even in development mode, it didn't reload the
classes.

However, a simple work-around of using 'require' on the lib scripts
made the problem go away. So the model contains the following (where
the 'Mod' module is defined in the script lib/my_lib/mod.rb):

require 'my_lib/mod'
include MyLib::Mod

I don't think this is all that beautiful, but maybe someday I'll learn
the proper way to do this.

n