Ruby: require vs require_relative - best practice to workaround running in both Ruby <1>=1.9.2

Question

What is the best practice if I want to require a relative file in Ruby and I want it to work in both 1.8.x and >=1.9.2?

I see a few options:

Answer 1

If you were building a gem, you would not want to pollute the load path.

But, In the case of a standalone application it is very convenient to just add the current directory to the load path as you do in the first 2 examples.

My vote goes to the first option on the list.

I would love to see some solid Ruby best practices literature.

Answer 2

The Pickaxe has a snippet for this for 1.8. Here it is:

def require_relative(relative_feature)
  c = caller.first
  fail "Can't parse #{c}" unless c.rindex(/:\d+(:in `.*')?$/)
  file = $`
  if /\A\((.*)\)/ =~ file # eval, etc.
    raise LoadError, "require_relative is called in #{$1}"
  end
  absolute = File.expand_path(relative_feature, File.dirname(file))
  require absolute
end

It basically just uses what Theo answered, but so you can still use require_relative.

Answer 3

$LOAD_PATH << '.'

$LOAD_PATH << File.dirname(__FILE__)

It's not a good security habit: why should you expose your whole directory?

require './path/to/file'

This doesn't work if RUBY_VERSION < 1.9.2

use weird constructions such as

require File.join(File.dirname(__FILE__), 'path/to/file')

Even weirder construction:

require File.join(File.expand_path(File.dirname(__FILE__)), 'path/to/file')

Use backports gem - it's kind of heavy, it requires rubygems infrastructure and includes tons of other workarounds, while I just want require to work with relative files.

You have already answered why these are not the best options.

check if RUBY_VERSION < 1.9.2, then define require_relative as require, use require_relative everywhere where it's needed afterwards

check if require_relative already exists, if it does, try to proceed as in previous case

This may work, but there's safer and quicker way: to deal with the LoadError exception:

begin
  # require statements for 1.9.2 and above, such as:
  require "./path/to/file"
  # or
  require_local "path/to/file"
rescue LoadError
  # require statements other versions:
  require "path/to/file"
end

Answer 4

A workaround for this was just added to the 'aws' gem so thought I'd share as it was inspired by this post.

https://github.com/appoxy/aws/blob/master/lib/awsbase/require_relative.rb

unless Kernel.respond_to?(:require_relative)
  module Kernel
    def require_relative(path)
      require File.join(File.dirname(caller[0]), path.to_str)
    end
  end
end

This allows you to use require_relative as you would in ruby 1.9.2 in ruby 1.8 and 1.9.1.

Answer 5

The backports gem now allows individual loading of backports.

You could then simply:

require 'backports/1.9.1/kernel/require_relative'
# => Now require_relative works for all versions of Ruby

This require will not affect newer versions, nor will it update any other builtin methods.

Answer 6

Another option is to tell the interpreter which paths to search

ruby -I /path/to/my/project caller.rb