'Gem::Server#run': uninitialized constant RDoc::Servlet (NameError) in Ruby 4.1.0dev

[junaruga]

I am using ruby and gem commands at a relatively latest ruby/ruby master branch ruby/ruby@7d4941d.

Summary

I created the following testing ruby script written on the README.md.

bin/gem_server.rb

gem_server = Gem::Server.new Gem.dir, 8089, false
gem_server.run

Then I got the following error. I expected that I didn't need to require the rubygem-server due to the gem plugin feature lib/rubygems_plugin.rb in this repository. But it seems it is actually required. Did you intend the testing ruby script works without require 'rubygems/server'?

$ ruby bin/gem_server.rb
bin/gem_server.rb:1:in '<main>': uninitialized constant Gem::Server (NameError)

gem_server = Gem::Server.new Gem.dir, 8089, false
                ^^^^^^^^
Did you mean?  Gem::Resolver

Then I updated bin/gem_server.rb adding the require 'rubygems/server'.

bin/gem_server.rb

require 'rubygems/server'

gem_server = Gem::Server.new Gem.dir, 8089, false
gem_server.run

I got the following error.

$ ruby bin/gem_server.rb
Server started at http://0.0.0.0:8089
Server started at http://[::]:8089
/home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/lib/ruby/gems/4.1.0+1/gems/rubygems-server-0.3.0/lib/rubygems/server.rb:825:in 'Gem::Server#run': uninitialized constant RDoc::Servlet (NameError)

      @server.mount '/doc_root', RDoc::Servlet, '/doc_root'
                                     ^^^^^^^^^
Did you mean?  RDoc::Server
	from bin/gem_server.rb:4:in '<main>'

https://github.com/rubygems/rubygems-server/blob/55a910c18412213e960c385642f2a7dc6a98f36d/lib/rubygems/server.rb#L825

The ruby/rdoc repository renamed the RDoc::Servlet to RDoc::RI::Servlet at ruby/rdoc@3c6f5f6. So, I assume this repository need to apply the RDoc::RI::Servlet or RDoc::Servlet conditionally. Or add the compatible RDoc::Servlet class being alias of the RDoc::RI::Servlet to ruby/rdoc.

My environment

$ which ruby
~/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/bin/ruby

$ ruby -v
ruby 4.1.0dev (2026-04-23T04:48:32Z master 7d4941d3e1) +PRISM [x86_64-linux]

$ which gem
~/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/bin/gem

$ gem env
RubyGems Environment:
  - RUBYGEMS VERSION: 4.1.0.dev
  - RUBY VERSION: 4.1.0 (2026-04-23 patchlevel -1) [x86_64-linux]
  - INSTALLATION DIRECTORY: /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/lib/ruby/gems/4.1.0+1
  - USER INSTALLATION DIRECTORY: /home/jaruga/.local/share/gem/ruby/4.1.0+1
  - CREDENTIALS FILE: /home/jaruga/.local/share/gem/credentials
  - RUBY EXECUTABLE: /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/bin/ruby
  - GIT EXECUTABLE: /bin/git
  - EXECUTABLE DIRECTORY: /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/bin
  - SPEC CACHE DIRECTORY: /home/jaruga/.cache/gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/etc
  - RUBYGEMS PLATFORMS:
     - ruby
     - x86_64-linux
  - GEM PATHS:
     - /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/lib/ruby/gems/4.1.0+1
     - /home/jaruga/.local/share/gem/ruby/4.1.0+1
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => true
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/bin
     - /usr/local/wasmtime-1.0.1/bin
     - /home/jaruga/.go/bin
     - /home/jaruga/git/gem2rpm/bin
     - /home/jaruga/git/rpmlint/dist/usr/bin
     - /bin
     - /usr/bin
     - /usr/sbin
     - /usr/local/bin
     - /usr/local/sbin
     - /home/jaruga/bin
     - /home/jaruga/.local/bin
     - /home/jaruga/.local/FASTK-f18a4e6/bin
     - /home/jaruga/.local/GENESCOPE.FK-380815c/bin
     - /home/jaruga/.local/MERQURY.FK-8f3ab70/bin
     - /var/lib/snapd/snap/bin
     - /usr/local/powercap/bin
     - /usr/local/mongodb-linux-x86_64-rhel80-4.4.1/bin
     - /home/jaruga/.npm-global/bin

$ gem info rubygems-server

*** LOCAL GEMS ***

rubygems-server (0.3.0)
    Author: Hiroshi SHIBATA
    Homepage: https://github.com/rubygems/rubygems-server
    License: MIT
    Installed at: /home/jaruga/.local/ruby-4.1.0-debug-7d4941d3e1-openssl-4.1.0-5e32b3e3fa/lib/ruby/gems/4.1.0+1

    Gem::Server and allows users to serve gems for consumption by `gem
    --remote-install`.

[junaruga]

@hsbt @st0012 What do you think? How to fix this issue?

[junaruga]

I sent the following PRs related to this issue.

• README.md: Usage: Add require 'rubygems/server' #13
• Fix handling RDoc::Servlet rename to RDoc::RI::Servlet #14

[st0012]

Since this project depends on RDoc's API, it should declare rdoc as its dependency.
And once RDoc 8.0 is released, we can then simplify #14 and bump to use RDoc 8.0.