Why isn't current directory on my Ruby path?

Question

Is there any reason why my present working directory is not on my Ruby path?

Consider:

~:499$ irb
ruby-1.9.2-p136 :002 > puts $:
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/site_ruby/1.9.1
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/site_ruby/1.9.1/x86_64-darwin10.6.0
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/site_ruby
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/vendor_ruby/1.9.1
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/vendor_ruby/1.9.1/x86_64-darwin10.6.0
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/vendor_ruby
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1
/Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/x86_64-darwin10.6.0
 => nil 

This is really bothering me because require isn't working as I thought it would (although I'm a ruby nuby):

require 'some_file_that_I_know_darn_well_is_in_pwd.rb'

If I append '.' to the end, then the require works as I'd expect.

What am I missing?

---

UPDATE:

Arg! Now I'm getting a new problem. Consider:

ruby-1.9.2-p136 :010 > `ls`
 => "start.rb\n" 
ruby-1.9.2-p136 :011 > require_relative 'start'
LoadError: cannot infer basepath
    from (irb):11:in `require_relative'
    from (irb):11
    from /Users/mrberryman/.rvm/rubies/ruby-1.9.2-p136/bin/irb:16:in `<main>'

Now what's up?

Answer 1

In Ruby 1.9.2 the Powers that Be introduced an explicit change so that the working directory is no longer in the Ruby path. I thought it was the Apocalypse and a terrible thing, until I learned about require_relative. My apps tend to look like this:

require 'some_gem'
require 'another_gem'
require_relative 'lib/init'

And then lib/init.rb can have:

require_relative 'lib1' # this is lib/lib1.rb
require_relative 'lib2' # this is lib/lib2.rb

It's the bees knees, and solves all sorts of problems I used to have with requiring the same file from different working directories.

Edit: Unfortunately (for reasons I don't know and haven't looked into) require_relative doesn't work specifically in irb. For this you can:

1. do what you initially described: either $: << '.' or $:.unshift '.', or

2. you can use load 'myfile.rb' or require './myfile' instead:

   irb(main):001:0> Dir['*.rb']
   => ["a.rb", "bar.rb", "foo.rb", "prime.rb", "tmp.rb"]
   
   irb(main):002:0> require 'a'
   LoadError: no such file to load -- a
     from <internal:lib/rubygems/custom_require>:29:in `require'
     from <internal:lib/rubygems/custom_require>:29:in `require'
     from (irb):2
     from /usr/local/bin/irb:12:in `<main>'
   
   irb(main):003:0> require_relative 'a'
   LoadError: cannot infer basepath
     from (irb):3:in `require_relative'
     from (irb):3
     from /usr/local/bin/irb:12:in `<main>'
   
   irb(main):004:0> load 'a.rb'
   a
   => true
   
   irb(main):005:0> require './a'
   a
   => true