From: Paul Brannan <paul@...>
Date: 2002-02-22T08:54:07+09:00
Subject: Re: recursive require

On Fri, Feb 22, 2002 at 07:39:06AM +0900, Ron Jeffries wrote:
> I'm having a really odd thing happen with two files that mutually
> require each other, and I'm hoping for help.

Having two files that mutually require each other is almost always a
bug.  I'm not sure you've convinced me that you have a good reason to do
this.

> I have a file of code and a corresponding file of tests. They have the
> same main program, which is to run the tests (unless there's something
> in the args, as usual).
> 
> So I set up the code file to require the tests file and the tests file
> to require the code file.

I understand why the tests depend on the code, but why must the code
depend on the tests?

> It turns out that, if I start to run, say, the code, Ruby will
> 
> begin code
> 	code requires tests:
> 	begin tests
> 		tests requires code:
> 		begin code
> 			code requires tests:
> 			tests load = false
> 		end code
> 		defining code classes ****
> 		code load = true
> 	end tests
> 	defining test classes
> 	tests load = true
> end code
> defining code classes ****

I can reproduce this in a small test case.  It appears that if I add the
following to the top of both code.rb and tests.rb:

  $".push(__FILE__)

then I get the following output:

  begin code
    code requires tests:
      begin tests
        tests requires code:
        code load = false
        defining test classes
        done defining test classes
      end tests
    tests load = true
    defining code classes
    done defining code classes
  end code

Note that because the tests are defined first, they cannot use any
constants defined in the code classes.

> The above is an actual printout from the program, except that I manually
> tabbed it to make it easier to read.

I've written an "iputs" method and I manipulate $indent inside code.rb
and tests.rb to get my indentation.  Call me lazy. :)

> Note that the code classes are defined twice. If I do it the other way
> around, running the test file, then it happens the other way around: the
> tests are loaded twice and the test files defined twice.
> 
> Either way it's weird. Worst of all, the program runs differently
> depending which file I load first.
> 
> So ... any advice will be very welcome. What am I missing?

I don't have any good advice, but I think the old (possibly overused)
doctor patient joke applies here:

  Patient: "Hey Doc!  It hurts when I drop this anvil on my foot!"
  Doctor: "So don't drop an anvil on your foot!"

Hope this helps,

Paul