vendor/rails/activesupport/lib/active_support/core_ext/kernel/requires.rb

   1 module Kernel
   2   # Require a library with fallback to RubyGems.  Warnings during library
   3   # loading are silenced to increase signal/noise for application warnings.
   4   def require_library_or_gem(library_name)
   5     silence_warnings do
   6       begin
   7         require library_name
   8       rescue LoadError => cannot_require
   9         # 1. Requiring the module is unsuccessful, maybe it's a gem and nobody required rubygems yet. Try.
  10         begin
  11           require 'rubygems'
  12         rescue LoadError => rubygems_not_installed
  13           raise cannot_require
  14         end
  15         # 2. Rubygems is installed and loaded. Try to load the library again
  16         begin
  17           require library_name
  18         rescue LoadError => gem_not_installed
  19           raise cannot_require
  20         end
  21       end
  22     end
  23   end
  24 end