Bug #13932: [PATCH] Extension libraries take precedence in checks of later Kernel.#require calls for features without file extensions

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.5.0dev (2017-09-23 trunk 60002) [x86_64-linux]
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
• Tags: core

[akihikodaki (Akihiko Odaki)]

Extension libraries take precedence in checks of later Kernel.#require calls for features without file extensions. That behavior is inconsistent with the first call, and can cause problems.

For instance, feature openssl has openssl.rb and openssl.so, but it assumes openssl.rb will always be loaded when it gets required. That assumption works for the first call of Kernel.#require, but for the later calls, require assumes openssl.so is being required and checks if the file is valid for the requirement.

Usually that is not so problematic since it just check if openssl.so, which is already required by openssl.rb, is required or not. However, if there is a new alternative openssl.rb in $:, the file will be loaded and conflict with the feature already loaded.
The below is a code example.

p $:.include? '/usr/lib/ruby/2.4.0' # true
p $:.include? '/home/aki/mastodon/vendor/bundle/ruby/2.4.0/gems/openssl-2.0.5/lib' # false

p $".include? '/usr/lib/ruby/2.4.0/openssl/openssl.rb' # false
p $".include? '/home/aki/mastodon/vendor/bundle/ruby/2.4.0/gems/openssl-2.0.5/lib/openssl.rb' # false

require 'openssl'

p $".include? '/usr/lib/ruby/2.4.0/openssl/openssl.rb' # true
p $".include? '/home/aki/mastodon/vendor/bundle/ruby/2.4.0/gems/openssl-2.0.5/lib/openssl.rb' # false

$:.unshift '/home/aki/mastodon/vendor/bundle/ruby/2.4.0/gems/openssl-2.0.5/lib'
require 'openssl'

p $".include? '/home/aki/mastodon/vendor/bundle/ruby/2.4.0/gems/openssl-2.0.5/lib/openssl.rb' # true (unexpected)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed

This patch appears to change a general behavior of require even when extension libraries are not involved. For example, it changes the behavior of this code:

Dir.mkdir('a')
Dir.mkdir('b')
File.write('a/c.rb', '$a = 1')
File.write('b/c.rb', '$a = 2')

$:.unshift('a')
require 'c'
p $a
$:.unshift('b')
require 'c'
p $a
# Before: 2
# With Patch: 1

I don't think Ruby's current behavior here is a bug. require will not load the same file path a second time, but it will load a different file path for the same argument if there has been a change to the load path. The documentation for require describes this behavior: A file will not be loaded again if its path already appears in $" (saying nothing about the argument to require). As the current behavior does not appear to be a bug, I'm going to close this.