为什么找不到 mime-types gem（在 vendor/gems 中解压）？

Question

我问这个的目的也是为了提供答案，因为我在弄清楚出了什么问题时遇到了很多麻烦，而谷歌也没有太多帮助 - 但是，由于这是 StackOverflow，我'确信有人会更胜任地回答或改进答案。

我需要为我正在开发的 Rails 应用程序升级 gem，它引入了两个新的依赖项，其中一个是 mime-types。在本地工作，我将以下行添加到config/environment.rb：

config.gem 'mime-types', :version => '1.17'

为了在我们的服务器上进行部署，所有 gem 依赖项都必须安装在 vendor/gems 中，因此我随后将 mime-types gem 安装到当前 rvm gemset 中：

gem install mime-types --version 1.17

...并将其版本解压到vendor/gems 中：

rake gems:unpack
rake gems:unpack:dependencies

但是，在服务器上部署后，我发现在运行rake db:migrate时，出现如下错误，提示找不到mime-types gem（堆栈跟踪部分省略）：

no such file to load -- mime-types
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
[...]
/lib/tasks/misc.rake:4
/usr/lib/ruby/1.8/rake.rb:636:in `call'
/usr/lib/ruby/1.8/rake.rb:636:in `execute'
/usr/lib/ruby/1.8/rake.rb:631:in `each'
/usr/lib/ruby/1.8/rake.rb:631:in `execute'
/usr/lib/ruby/1.8/rake.rb:597:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/rake.rb:590:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/rake.rb:607:in `invoke_prerequisites'
/usr/lib/ruby/1.8/rake.rb:604:in `each'
/usr/lib/ruby/1.8/rake.rb:604:in `invoke_prerequisites'
/usr/lib/ruby/1.8/rake.rb:596:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/rake.rb:590:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/rake.rb:583:in `invoke'
/usr/lib/ruby/1.8/rake.rb:2051:in `invoke_task'
/usr/lib/ruby/1.8/rake.rb:2029:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2029:in `each'
/usr/lib/ruby/1.8/rake.rb:2029:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:2023:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2001:in `run'
/usr/lib/ruby/1.8/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:1998:in `run'
/usr/bin/rake:28
no such file to load -- mime-types
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
[...]
/lib/tasks/misc.rake:4
/usr/lib/ruby/1.8/rake.rb:636:in `call'
/usr/lib/ruby/1.8/rake.rb:636:in `execute'
/usr/lib/ruby/1.8/rake.rb:631:in `each'
/usr/lib/ruby/1.8/rake.rb:631:in `execute'
/usr/lib/ruby/1.8/rake.rb:597:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/rake.rb:590:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/rake.rb:607:in `invoke_prerequisites'
/usr/lib/ruby/1.8/rake.rb:604:in `each'
/usr/lib/ruby/1.8/rake.rb:604:in `invoke_prerequisites'
/usr/lib/ruby/1.8/rake.rb:596:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/rake.rb:590:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/rake.rb:583:in `invoke'
/usr/lib/ruby/1.8/rake.rb:2051:in `invoke_task'
/usr/lib/ruby/1.8/rake.rb:2029:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2029:in `each'
/usr/lib/ruby/1.8/rake.rb:2029:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:2023:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2001:in `run'
/usr/lib/ruby/1.8/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:1998:in `run'
/usr/bin/rake:28
Missing these required gems:
  mime-types = 1.17

You're running:
  ruby 1.8.7.302 at /usr/bin/ruby1.8
  rubygems 1.3.7 at /home/mark/.gem/ruby/1.8, /var/lib/gems/1.8

Run `rake gems:install` to install the missing gems.

但是，mime-types 出现在 vendor/gems/mime-types-1.17 中。这种情况下rake为什么不认为安装了gem？

Answer 1

一位同事帮我解决了这个问题：Rails 似乎希望 vendor/gems 中的所有 gem 具有特定的布局，而 mime-types 不符合。解决方案是更改environment.rb 中指定对mime-type 的依赖关系的行以添加:lib 选项，该选项应指定指示如何获取gem 中源的相对路径：

config.gem 'mime-types', :version => '1.17', :lib => 'mime/types'

这意味着查看 vendor/gems/mime-types-1.17/lib/mime/types 而不是基于 gem 名称的默认值 vendor/gems/mime-types-1.17/lib/mime-types/

Answer 2

只需删除 ruby​​ 文件中的 require 'mime-types'。

mime-types 是用 ruby​​ 构建的。你不需要安装它的 gem 或者明确地包含它。

只要使用它。 这对我有用。