💎 Appraisal2::Rubocop

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I've summarized my thoughts in this blog post.

Runs RuboCop against Appraisal2-generated gemfiles via Appraisal2 lifecycle hooks.

This plugin is intended for modern Ruby style-maintenance environments. It does not match Appraisal2's legacy runtime floor.

Load it as an Appraisal2 generator plugin, and make its RuboCop toolchain available only to the generator bundle.

Tokens to Remember
Works with JRuby
Works with Truffle Ruby
Works with MRI Ruby 4
Works with MRI Ruby 3
Support & Community
Source
Documentation
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Maintainer 🎖️
... 💖	🧊 🐙 🛖 🧪

Compatible with MRI Ruby 3.1.0+, and concordant releases of JRuby, and TruffleRuby. CI workflows and Appraisals are generated for MRI Ruby 3.1.0+. This test floor is configured by ruby.test_minimum in .kettle-jem.yml and may be higher than the gem's runtime compatibility floor when legacy Rubies are not practical for the current toolchain.

Federated DVCS Repository	Status	Issues	PRs	Wiki	CI	Discussions
🧪 appraisal-rb/appraisal2-rubocop on GitLab	The Truth	💚	💚	💚	🐭 Tiny Matrix	➖
🧊 appraisal-rb/appraisal2-rubocop on CodeBerg	An Ethical Mirror (Donate)	💚	💚	➖	⭕️ No Matrix	➖
🐙 appraisal-rb/appraisal2-rubocop on GitHub	Another Mirror	💚	💚	💚	💯 Full Matrix	💚
🎮️ Discord Server		Let's	talk	about	this	library!

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Alternatively:

Install the gem and add to the application's Gemfile by executing:

bundle add appraisal2-rubocop

If bundler is not being used to manage dependencies, install the gem by executing:

gem install appraisal2-rubocop

• APPRAISAL2_RUBOCOP=false disables the hook.
• APPRAISAL2_RUBOCOP_COMMAND overrides the executable.
• APPRAISAL2_RUBOCOP_FLAGS overrides the default --autocorrect flag list.

Add the plugin to the style toolchain used by the Appraisal root bundle:

# gemfiles/modular/style.gemfile
gem "appraisal2-rubocop", "~> 0.1", ">= 0.1.0", require: false

Expose that style toolchain only to the Appraisal generator bundle:

# Appraisal.root.gemfile
if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("3.2")
  if respond_to?(:generator_only)
    generator_only do
      eval_gemfile "gemfiles/modular/style.gemfile"
    end
  else
    eval_gemfile "gemfiles/modular/style.gemfile"
  end
end

The respond_to?(:generator_only) split is for the two DSLs that read this file: Appraisal2 uses the generator_only block when building generated appraisal gemfiles, while Bundler evaluates the same file to install the generator bundle.

Load the plugin from Appraisals:

plugin "appraisal2-rubocop", require: "appraisal2/rubocop", optional: true

By default each generated gemfile is processed in memory with:

rubocop --stdin path/to/generated.gemfile --autocorrect --stderr --format quiet

While appraisal-rb tools are free software and will always be, the project would benefit immensely from some funding. Raising a monthly budget of... "dollars" would make the project more sustainable.

We welcome both individual and corporate sponsors! We also offer a wide array of funding channels to account for your preferences. Currently, Open Collective is our preferred funding platform.

If you're working in a company that's making significant use of appraisal-rb tools we'd appreciate it if you suggest to your company to become a appraisal-rb sponsor.

You can support the development of appraisal-rb tools via GitHub Sponsors, Liberapay, PayPal, Open Collective and Tidelift.

Support us with a monthly donation and help us continue our activities. [Become a backer]

NOTE: kettle-readme-backers updates this list every day, automatically.

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Become a sponsor and get your logo on our README on GitHub with a link to your site. [Become a sponsor]

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I’m driven by a passion to foster a thriving open-source community – a space where people can tackle complex problems, no matter how small. Revitalizing libraries that have fallen into disrepair, and building new libraries focused on solving real-world challenges, are my passions. I was recently affected by layoffs, and the tech jobs market is unwelcoming. I’m reaching out here because your support would significantly aid my efforts to provide for my family, and my farm (11 🐔 chickens, 2 🐶 dogs, 3 🐰 rabbits, 8 🐈‍ cats).

If you work at a company that uses my work, please encourage them to support me as a corporate sponsor. My work on gems you use might show up in bundle fund.

I’m developing a new library, floss_funding, designed to empower open-source developers like myself to get paid for the work we do, in a sustainable way. Please give it a look.

Floss-Funding.dev: 👉️ No network calls. 👉️ No tracking. 👉️ No oversight. 👉️ Minimal crypto hashing. 💡 Easily disabled nags

See SECURITY.md.

If you need some ideas of where to help, you could work on adding more code coverage, or if it is already 💯 (see below) check issues or PRs, or use the gem and think about how it could be better.

We so if you make changes, remember to update it.

See CONTRIBUTING.md for more detailed instructions.

See CONTRIBUTING.md.

Everyone interacting with this project's codebases, issue trackers, chat rooms and mailing lists agrees to follow the .

Made with contributors-img.

Also see GitLab Contributors: https://gitlab.com/appraisal-rb/appraisal2-rubocop/-/graphs/main

This library follows for its public API where practical. For most applications, prefer the Pessimistic Version Constraint with two digits of precision.

For example:

spec.add_dependency("appraisal2-rubocop", "~> 0.0")

Dropping support for a platform can be a breaking change for affected users. If a release changes supported platforms, it should be called out clearly in the changelog and versioned with that impact in mind.

To get a better understanding of how SemVer is intended to work over a project's lifetime, read this article from the creator of SemVer:

• "Major Version Numbers are Not Sacred"

See CHANGELOG.md for a list of releases.

The gem is available as open source under the terms of the MIT .

See LICENSE.md for the official copyright notice.

• Copyright (c) 2026 Peter H. Boling

Maintainers have teeth and need to pay their dentists. After getting laid off in an RIF in March, and encountering difficulty finding a new one, I began spending most of my time building open source tools. I'm hoping to be able to pay for my kids' health insurance this month, so if you value the work I am doing, I need your support. Please consider sponsoring me or the project.

To join the community or get help 👇️ Join the Discord.

To say "thanks!" ☝️ Join the Discord or 👇️ send money.

💌 💌 💌

Many parts of this project are actively managed by a kettle-jem smart template utilizing StructuredMerge.org merge contracts.

Thanks for RTFM. ☺️