hook = lambda do |installer|
  begin
    # Ignore gems that aren't installed in locations that rbenv searches for binstubs
    if installer.spec.executables.any? &&
        [Gem.default_bindir, Gem.bindir(Gem.user_dir)].include?(installer.bin_dir)
      `rbenv rehash`
    end
  rescue
    warn "rbenv: error in gem-rehash (#{$!.class.name}: #{$!.message})"
  end
end

if defined?(Bundler::Installer) &&
   Bundler::Installer.private_method_defined?(:install) &&
   !Bundler::Installer.private_method_defined?(:install_without_rbenv_rehash)
  Bundler::Installer.class_eval do
    private

    alias install_without_rbenv_rehash install
    def install(options)
      begin
        if Gem.default_path.include?(Bundler.bundle_path.to_s)
          bin_dir = Gem.bindir(Bundler.bundle_path.to_s)
          bins_before = File.exist?(bin_dir) ? Dir.entries(bin_dir).size : 2
        end
      rescue
        warn "rbenv: error in Bundler post-install hook (#{$!.class.name}: #{$!.message})"
      end

      result = install_without_rbenv_rehash(options)

      if bin_dir && File.exist?(bin_dir) && Dir.entries(bin_dir).size > bins_before
        `rbenv rehash`
      end
      result
    end
  end
else
  begin
    Gem.post_install(&hook)
    Gem.post_uninstall(&hook)
  rescue
    warn "rbenv: error installing gem-rehash hooks (#{$!.class.name}: #{$!.message})"
  end
end