Tooling

The build, lint, and quality tooling that backs every MR.

Linters and formatters

Tool	What it lints	Config
RuboCop	Ruby style + ~150 GitLab cops	.rubocop.yml, rubocop/cop/, .rubocop_todo/
HAML-Lint	HAML views	.haml-lint.yml
ESLint	JS / Vue	eslint.config.mjs (~28K LoC), .eslint_todo/
Stylelint	SCSS	.stylelintrc
Prettier	JS / Vue / Markdown formatting	.prettierrc
markdownlint	Markdown style	.markdownlint-cli2.yaml
Vale	Documentation prose	.vale.ini
yamllint	YAML	.yamllint
gettext-lint	i18n strings	invoked from scripts/i18n_*
golangci-lint	Workhorse Go	workhorse/.golangci.yml
Gitleaks	secret scanning	.gitleaks.toml

The "todo" subdirectories (.rubocop_todo/, .eslint_todo/) hold per-rule allowlists that gradually shrink as code is fixed.

Custom GitLab RuboCop cops

rubocop/cop/gitlab/ defines GitLab-specific cops, including:

• BoundedContexts — enforces namespace registration.
• FeatureCategory — requires a category on every controller, service, worker.
• MissingFeatureCategory — same, for Gemfile entries.
• ChangeTimezone — bans Time.now; use Time.zone.now.
• PolicyRuleBoolean — guards declarative_policy idioms.
• BulkInsert — flags non-bulk insert patterns in migrations.
• Many more under rubocop/cop/.

The cop list is curated; if you find yourself adding # rubocop:disable, justify it with a reference to a follow-up issue.

Lefthook

Local pre-push and pre-commit hooks are managed by Lefthook (lefthook.yml). It runs only on changed files for fast feedback. The config (~17K LoC) covers all linters above plus migration validators.

Install: lefthook install Bypass: LEFTHOOK=0 git push (discouraged).

Danger

The Danger bot runs in CI and posts MR comments. Rules live in danger/ (~58 subdirectories, one per rule). Examples:

• danger/changelog/ — warns when a user-visible change has no changelog trailer.
• danger/database/ — flags migration risk.
• danger/feature_flag/ — verifies feature flag YAML hygiene.
• danger/code_review/ — suggests reviewers and maintainers.
• danger/sidekiq_queues/ — flags untagged or new queues.
• danger/specs/ — warns about feature category metadata, ee/foss split, etc.

The Dangerfile at the repo root composes all rules.

Housekeeper

gems/gitlab-housekeeper/ and keeps/ are an automated MR generator. A "keep" describes a code transformation; the housekeeper runs them on a schedule and opens MRs for human review. Examples in keeps/:

• Removing rolled-out feature flags.
• Migrating tables to bigint.
• Refreshing dependency lists.

Build tools

Asset	Tool	Config
Main JS bundle	Webpack	config/webpack.config.js
Frontend islands	Vite	vite.config.js, config/vite.json
Tailwind	PostCSS + Tailwind	config/tailwind.config.js, postcss.config.js
GraphQL schema	graphql-ruby rake task	bin/rake gitlab:graphql:schema:dump
OpenAPI for some APIs	Grape OpenAPI gem	config/open_api.yml
Migration regeneration	scripts/regenerate-schema	—

CI templates

.gitlab/ci/ holds dozens of reusable templates split by stage and concern. Top-level template files include:

• lint.gitlab-ci.yml
• frontend.gitlab-ci.yml
• rspec.gitlab-ci.yml
• qa.gitlab-ci.yml
• pages.gitlab-ci.yml
• setup-test-env.gitlab-ci.yml

The root .gitlab-ci.yml includes them. Pipelines branch by:

• MR type (community vs internal).
• Ruby version (default vs rails-next).
• AIGW-triggered runs (TRIGGERED_BY_AI_GATEWAY_PROJECT).
• Stable branches and security mirror sync.

Generators

generator_templates/ and lib/generators/ hold custom Rails generators:

• bin/rails generate migration ...
• bin/rails generate event ... for EventStore events.
• bin/rails generate gitlab:internal_event ... for product analytics.

Gemfile.next pattern

The repo dual-tracks Ruby/Rails upgrades:

• Gemfile — pinned to the current shipping Ruby/Rails.
• Gemfile.next — symlinks to Gemfile but is loaded with BUNDLE_GEMFILE=Gemfile.next and next? switches in the Gemfile DSL pick alternate versions.

CI runs both pipelines so upgrades land without a long-lived branch.

Schema and data validators

Several scripts run in CI to keep the database safe:

• scripts/validate_migration_checksum
• scripts/validate_migration_schema
• scripts/validate_migration_timestamps
• scripts/validate_name_collisions_between_migrations
• scripts/validate_loose_foreign_keys_ordering
• scripts/validate_schema_changes

i18n / docs / link checking

• scripts/i18n_lint_doc.sh — Vale + Markdown lint pass on docs.
• scripts/lint-docs-redirects.rb — keeps docs redirects coherent.
• scripts/lint-docs-link-check.sh — broken link detector.

Where to add new tooling

• A new RuboCop cop: rubocop/cop/gitlab/<your_cop>.rb plus rubocop/cop/gitlab.rb registration.
• A new Danger rule: danger/<your_rule>/Dangerfile.
• A new keep: keeps/<your_keep>.rb.
• A new linter: a stage in .gitlab/ci/lint.gitlab-ci.yml plus a Lefthook entry.