brew/.github/copilot-instructions.md

Copilot Instructions for Homebrew/brew

This is a Ruby based repository with Bash scripts for faster execution. It is primarily responsible for providing the brew command for the Homebrew package manager. Please follow these guidelines when contributing:

Code Standards

Required Before Each Commit

• Run brew typecheck to verify types are declared correctly using Sorbet. Individual files/directories cannot be checked. brew typecheck is fast enough to just be run globally every time.
• Run brew style --fix --changed to lint code formatting using RuboCop. Individual files can be checked/fixed by passing them as arguments e.g. `brew style --fix Library/Homebrew/cmd/reinstall.rb``
• Run brew tests --online --changed to ensure that RSpec unit tests are passing (although some online tests may be flaky so can be ignored if they pass on a rerun). Individual test files can be passed with --only e.g. to test Library/Homebrew/cmd/reinstall.rb with Library/Homebrew/test/cmd/reinstall_spec.rb run brew tests --only=cmd/reinstall.
• All of the above can be run with the brew-mcp-server

Development Flow

• Write new code (using Sorbet sig type signatures and typed: strict for new files, but never for RSpec/test/*_spec.rb files)
• Write new tests (avoid more than one :integration_test per file for speed). Use only one expect assertion per test.
• Keep comments minimal; prefer self-documenting code through strings, variable names, etc. over more comments.

Repository Structure

• bin/brew: Homebrew's brew command main Bash entry point script
• completions/: Generated shell (bash/fish/zsh) completion files. Don't edit directly, regenerate with brew generate-man-completions
• Library/Homebrew/: Homebrew's core Ruby (with a little bash) logic.
• Library/Homebrew/bundle/: Homebrew's brew bundle command.
• Library/Homebrew/cask/: Homebrew's Cask classes and DSL.
• Library/Homebrew/extend/os/: Homebrew's OS-specific (i.e. macOS or Linux) class extension logic.
• Library/Homebrew/formula.rb: Homebrew's Formula class and DSL.
• docs/: Documentation for Homebrew users, contributors and maintainers. Consult these for best practices and help.
• manpages/: Generated man documentation files. Don't edit directly, regenerate with brew generate-man-completions
• package/: Files to generate the macOS .pkg file.

Key Guidelines

1. Follow Ruby and Bash best practices and idiomatic patterns.
2. Maintain existing code structure and organisation.
3. Write unit tests for new functionality.
4. Document public APIs and complex logic.
5. Suggest changes to the docs/ folder when appropriate
6. Follow software principles such as DRY and YAGNI.
7. Keep diffs as minimal as possible.