如何要求rubygems帮助找到rubygem文件？

问题描述

尝试解决。 （编辑： ）

文件说：

它通过打开模块Kernel 并使用别名对别名进行别名gem_original_require require ，然后重新定义 require 首先调用原始版本，如果不起作用，请查看gem。

  ruby​​-1.8.7-p330：002> $ :.长度
 => 9 
 ruby​​-1.8.7-p330：003>要求'rubygems'
 => true 
 ruby​​-1.8.7-p330：004> $ :.长度
 => 9 
 ruby​​-1.8.7-p330：005>需要'haml'
 => true 
 ruby​​-1.8.7-p330：006> $ :.长度
 => 10 
  

While trying to solve Gem found in irb, not in Ruby , I tried seeing what effect require 'rubygems' had on my own installation:

$ irb
irb(main):001:0> RUBY_VERSION
=> "1.8.7"
irb(main):002:0> $:
["/usr/local/lib/site_ruby/1.8", "/usr/local/lib/site_ruby/1.8/x86_64-linux", "/usr/local/lib/site_ruby", "/usr/lib/ruby/vendor_ruby/1.8", "/usr/lib/ruby/vendor_ruby/1.8/x86_64-linux", "/usr/lib/ruby/vendor_ruby", "/usr/lib/ruby/1.8", "/usr/lib/ruby/1.8/x86_64-linux", "."]
=> nil
irb(main):003:0> require "rubygems" # Hasn't been required already
=> true
irb(main):004:0> require "rubygems" # Will return false, because it's already been required
=> false
irb(main):005:0> $: # Same as before
=> ["/usr/local/lib/site_ruby/1.8", "/usr/local/lib/site_ruby/1.8/x86_64-linux", "/usr/local/lib/site_ruby", "/usr/lib/ruby/vendor_ruby/1.8", "/usr/lib/ruby/vendor_ruby/1.8/x86_64-linux", "/usr/lib/ruby/vendor_ruby", "/usr/lib/ruby/1.8", "/usr/lib/ruby/1.8/x86_64-linux", "."]

If requring rubygems doesn't modify $:, then how does it help find files? Does it monkeypatch require? If so, what variable does it use to find rubygem-installed libraries?

解决方案

Here's the current version of the relevant source: https://github.com/rubygems/rubygems/blob/02ead548e38ff90923444fa7c0ff9f6a5dbd87b0/lib/rubygems/custom_require.rb. (Edit: here's an earlier version (1.5.2) that more clearly expresses what happens.)

The docs say:

It does this by opening up module Kernel and aliasing the original require with alias gem_original_require require, then redefining require to first call the original version, and look at the gems if that doesn't work.

So the load path is only changed when you require a gem:

ruby-1.8.7-p330 :002 > $:.length
=> 9 
ruby-1.8.7-p330 :003 > require 'rubygems'
=> true 
ruby-1.8.7-p330 :004 > $:.length
=> 9 
ruby-1.8.7-p330 :005 > require 'haml'
=> true 
ruby-1.8.7-p330 :006 > $:.length
=> 10 

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