Claude Code /new-gem skill: Bootstrap a Ruby gem with RSpec, RuboCop, CI, and standard metadata

new-gem.md

name	new-gem
description	Bootstrap a new Ruby gem with RSpec, RuboCop, rubocop-rspec, SimpleCov, CI, and standard metadata.

Bootstrap a new Ruby gem using the arguments provided: $ARGUMENTS

The arguments should be parsed as: GEM_NAME followed by an optional summary in quotes. Example: /new-gem my_gem "A short description of the gem"

Autonomy

All file edits, file creation, shell commands (bundle gem, bundle install, bundle exec rspec, bundle exec rubocop, rubocop -A), and generated-file modifications described in the steps below are pre-authorized by the user. Proceed through every step without pausing for confirmation. Only stop to ask if something fails unexpectedly or falls outside the scope of these steps.

Steps

1. Scaffold with bundle gem using these flags:

   • --test=rspec
   • --ci=github
   • --changelog
   • --linter=rubocop
   • --mit
   • --no-git (we manage git separately)
   • Do NOT use --rubocop (removed; --linter=rubocop covers it).
   • Do NOT use --ext unless the user explicitly requests a C extension.

2. Add rubocop-rspec, rubocop-performance, and simplecov to the Gemfile and update .rubocop.yml to load the RuboCop plugins (not require, which is deprecated in newer RuboCop):

   Add to the Gemfile:

   gem "simplecov", require: false

   Update .rubocop.yml:

   plugins:
     - rubocop-rspec
     - rubocop-performance
   
   AllCops:
     NewCops: enable
     TargetRubyVersion: 3.2

   Add SimpleCov to the top of spec/spec_helper.rb (before any other requires):

   require "simplecov"
   SimpleCov.start

3. Fill in gemspec metadata:

   • Set spec.summary to the provided summary (or a sensible placeholder).
   • Set spec.description to a longer form of the summary.
   • Remove or fill in any TODO strings so the gemspec is immediately valid.
   • Set spec.homepage, spec.metadata["source_code_uri"], and spec.metadata["changelog_uri"] to placeholder URLs the user can update later.
   • Ensure spec.required_ruby_version is set to >= 3.2.

4. Create a smoke spec at spec/<gem_name>_spec.rb:

   # frozen_string_literal: true
   
   RSpec.describe <GemModule> do
     it "has a version number" do
       expect(<GemModule>::VERSION).not_to be_nil
     end
   end

5. Create .rspec with:

   --require spec_helper
   --format documentation
   --color
   

6. Create .gitignore with:

   .rspec_status
   

7. Run validation:

   • bundle install
   • bundle exec rspec — confirm specs pass.
   • bundle exec rubocop — fix any auto-correctable offenses with rubocop -A, then report remaining issues.

8. Report results to the user: list created files, test results, and any RuboCop issues that need manual attention.

Optional: Create the GitHub repo and push

Run this section only when the user asks to push the gem to GitHub. These steps were proven out on the polysemic gem.

1. Confirm visibility with the user (public vs private) — this is a hard-to-reverse choice for anything sensitive, so ask before creating.

2. Update gemspec URLs from the placeholders to the real repo:

   • spec.homepage = "https://github.com/<owner>/<gem>"
   • spec.metadata["source_code_uri"] = "https://github.com/<owner>/<gem>"
   • spec.metadata["changelog_uri"] = "https://github.com/<owner>/<gem>/blob/main/CHANGELOG.md"

3. Replace placeholders in generated files:

   • LICENSE.txt — replace Copyright (c) <YEAR> TODO: Write your name with the real author.
   • Author/email in the gemspec, if still TODO.

4. Add /coverage/ to .gitignore so SimpleCov output isn't committed.

5. Init and commit:

   git init -b main
   git add <explicit list of files — do NOT use "git add ." since coverage/ may exist>
   git commit -m "Initial commit: scaffold <gem> gem"

6. Create the repo and push:

   gh repo create <owner>/<gem> \
     --private \                        # or --public per user choice
     --description "<gem summary>" \
     --source=. --remote=origin --push

7. If the push fails, diagnose and recover:

   • Permission denied (publickey) — the default SSH config can't reach GitHub for this account. Ask the user how they'd like to authenticate (e.g. a per-account SSH host alias they've configured locally). Do not guess the alias. Once they supply it, git remote set-url origin <their-url> and git push -u origin main.
   • refusing to allow an OAuth App to create or update workflow ... without 'workflow' scope — the gh token lacks the workflow scope needed to push .github/workflows/main.yml. Either switch to SSH or ask the user to run gh auth refresh -s workflow.

Constraints

• Do not create unnecessary files beyond what bundle gem and the steps above produce.
• Prefer editing generated files over creating new ones.
• Do not commit unless the user asks. The user has a separate /tasteful-commits command for that.

Future extensions

• Prompt the user for author name, email, and GitHub username instead of placeholders.
• Automate publishing to RubyGems.org (gem build + gem push).