comma: Instructions file for GitHub Copilot

Copilot instructions for comma

Build, test, and lint commands

This repository is a Ruby gem. Ruby 3.0+ is required, and the CI matrix exercises Ruby 3.0-3.4 against Rails/ActiveRecord appraisals from 6.0 through 7.1.

# install dependencies for the base Gemfile
bundle install

# install all appraisal Gemfiles used by CI
bundle exec appraisal install

# build the gem
bundle exec rake build

# lint
bundle exec rubocop -P
# or
bundle exec rake rubocop

# base test suite (runs non-Rails specs when framework gems are absent)
bundle exec rspec spec
# or
bundle exec rake spec

# run one example from the base suite
bundle exec rspec spec/comma/comma_spec.rb:205

# run the full multi-gemfile matrix locally
bundle exec appraisal rake spec

# run a single spec file under a specific appraisal
bundle exec appraisal active7.1.3 bundle exec rspec spec/comma/rails/active_record_spec.rb

# CI equivalent for a single matrix entry
BUNDLE_GEMFILE=gemfiles/rails7.1.3.gemfile bundle exec rspec spec/controllers/users_controller_spec.rb

High-level architecture

• lib/comma/object.rb adds the core DSL globally via Object.comma. Each class stores named format blocks in comma_formats, and subclasses inherit a shallow copy of those formats.
• lib/comma/extractor.rb is the shared execution engine. It instance_evals a stored format block and collects stringified results. The two concrete extractors split responsibilities:
  • lib/comma/data_extractor.rb resolves values from the instance or an associated object and applies optional block-based transformations.
  • lib/comma/header_extractor.rb derives headers from the same DSL and can map association columns to the associated model class for humanized labels.
• lib/comma/generator.rb is the only place that turns object rows into CSV output. Array, ActiveRecord::Relation, Mongoid::Criteria, and DataMapper::Collection each delegate to it from their own extension files.
• lib/comma.rb wires framework integrations lazily with ActiveSupport.on_load. That file is also where the Rails render csv: renderer is registered, so controller behavior is part of the gem's load path rather than test-only glue.
• Integration specs use the miniature app under spec/rails_app/ plus inline model definitions inside spec files. The base suite still runs without Rails, Mongoid, DataMapper, or ActiveRecord because integration examples are wrapped in if defined?(...) guards in the specs.