From: Robert Klemme <shortcutter@...>
Date: 2007-12-17T06:45:02+09:00
Subject: Re: magic / counter-magic? (detect loading file?)

On 16.12.2007 20:52, Giles Bowkett wrote:
> Here's something that's puzzling me.
> 
> Somewhere inside Rails is something which loads your .irbrc under some
> circumstances.

That sounds strange.  Why would a rails app need IRB?

> It means that if you have a gem which adds a lot of
> methods to Object and which is required by people in their .irbrcs,
> sooner or later, your methods on Object are going to collide with
> Rails' methods on *anything*. I have such a gem, Utility Belt, and
> this happened to somebody who installed it. It's going to happen to a
> lot of people, in fact, because the method in question was named
> "edit," which practically every Rails app uses.
> 
> I took a look around the Rails file-loading process and it looked
> pretty involved. I know the problem comes from
> ActiveSupport::Dependencies but that's about it. I'd like to find and
> fix the bug in Rails but I just don't have time. What I want to do
> instead is set up Utility Belt to recognize when it's being called
> from Rails and then have it de-borkify the situation. All I really
> need to accomplish that is code which can recognize where it's being
> called or loaded from. I know such code, and idioms for using it,
> exist, but I'm not sure what they are.

You can use caller to find out about the call stack:

irb(main):003:0> def f(n) caller(n) end
=> nil
irb(main):004:0> f 0
=> ["(irb):3:in `f'", "(irb):4:in `irb_binding'", 
"/usr/lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'", ":0"]
irb(main):005:0> f 1
=> ["(irb):5:in `irb_binding'", 
"/usr/lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'", ":0"]
irb(main):006:0> f 2
=> ["/usr/lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'", ":0"]

> Is it just a matter of grepping
> against __FILE__? How does my gem determine who it's being loaded by
> and send them away if they don't need to be loading it?

Alternatively you could set up tracing with set_trace_func and determine 
the calling chain that leads to this behavior by looking at the trace 
output.

Kind regards

	robert