This repo demonstrates a fundamental problem with Ruby 1.9’s strategy of putting the newest version of each gem on the load path.

You can see it in action by running rake test in each of 1.8 and 1.9.

In particular, because gem_prelude skips the gem activation step, having a newer version of a dependency of ANY gem will result in the newer version being used.

In this case, the dependency tree is:

rubygems-bug-parent
|- rubygems-bug-child 1.0

rubygems-bug-child 1.0
rubygems-bug-child 1.1

Triggering code:

require "rubygems"
require "rubygems-bug-parent"

In Ruby 1.8, requiring rubygems-bug-parent puts rubygems-bug-child 1.0 on the load path, so when it requires rubygems-bug-child, it gets 1.0.

In Ruby 1.9, rubygems-bug-child version 1.1 is already on the load path (since it’s the most recent version on your system). Since the Rubygems gem activation system is never loaded, require “rubygems-bug-parent” simply requires the rubygems-bug-child which is on the load path.

In my estimation, this demonstrates a fundamental flaw with the strategy of trying to avoid needing Rubygems for common gems. I recommend shipping with Rubygems as a standard library, but needing require “rubygems” (or -rubygems) to pull it in, just like any other standard library.