为什么找不到mime类型的gem (在供应商/宝石中解压缩)？

Question

我问这个问题的目的也是为了给出答案，因为我很难搞清楚到底出了什么问题，而谷歌对此帮助不大--不过，既然这是StackOverflow，我肯定有人会更胜任地回答这个问题，或者改进答案。

我需要为我正在开发的rails应用程序升级一个gem，它引入了两个新的依赖项，其中一个是mime-types。在本地工作时，我在config/environment.rb中添加了下面一行

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

为了在我们的服务器上进行部署，必须在vendor/gems中安装所有的gem依赖项，因此我将mime-types gem安装到当前的rvm gem集中，其中包括：

gem install mime-types --version 1.17

..。并将其解压缩到vendor/gems中，并使用：

rake gems:unpack
rake gems:unpack:dependencies

但是，在服务器上部署之后，我发现在运行rake db:migrate时，出现了以下错误，表明无法找到mime-types gem (堆栈跟踪部分被省略)：

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.

然而，mime-types存在于vendor/gems/mime-types-1.17中。为什么rake不认为在这种情况下安装了gem呢？

Answer 1

一位同事帮我解决了这个问题: Rails似乎希望vendor/gems中的所有宝石都有一个特定的布局，而mime-types不符合这个布局。解决方案是更改environment.rb中指定依赖于mime-type的行，以添加:lib选项，该选项应指定一个相对路径，该路径指示如何到达gem中的源：

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，而不是基于宝石名称vendor/gems/mime-types-1.17/lib/mime-types/的缺省值。

Answer 2

只需删除红宝石文件中的require 'mime-types'即可。

因为mime-types是用红宝石建造的。您不需要安装它的gem或显式地包含它。

就用它吧。这对我有用。