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diff --git a/doc/development/rubocop_development_guide.md b/doc/development/rubocop_development_guide.md new file mode 100644 index 00000000000..2ff94f65232 --- /dev/null +++ b/doc/development/rubocop_development_guide.md @@ -0,0 +1,114 @@ +--- +type: reference, dev +stage: none +group: Development +info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments +--- + +# RuboCop rule development guide + +Our codebase style is defined and enforced by [RuboCop](https://github.com/rubocop-hq/rubocop). + +You can check for any offenses locally with `bundle exec rubocop --parallel`. +On the CI, this is automatically checked by the `static-analysis` jobs. + +In addition, you can [integrate RuboCop](developing_with_solargraph.md) into +supported IDEs using the [Solargraph](https://github.com/castwide/solargraph) gem. + +For RuboCop rules that we have not taken a decision on, follow the [Ruby style guide](backend/ruby_style_guide.md) to write idiomatic Ruby. + +Reviewers/maintainers should be tolerant and not too pedantic about style. + +Some RuboCop rules are disabled, and for those, +reviewers/maintainers must not ask authors to use one style or the other, as both +are accepted. This isn't an ideal situation because this leaves space for +[bike-shedding](https://en.wiktionary.org/wiki/bikeshedding). Ideally we +should enable all RuboCop rules to avoid style-related +discussions, nitpicking, or back-and-forth in reviews. The +[GitLab Ruby style guide](backend/ruby_style_guide.md) includes a non-exhaustive +list of styles that commonly come up in reviews and are not enforced. + +Additionally, we have dedicated +[test-specific style guides and best practices](testing_guide/index.md). + +## Creating new RuboCop cops + +Typically it is better for the linting rules to be enforced programmatically as it +reduces the aforementioned [bike-shedding](https://en.wiktionary.org/wiki/bikeshedding). + +To that end, we encourage creation of new RuboCop rules in the codebase. + +Before adding a new cop to enforce a given style, make sure to discuss it with your team. + +We maintain cops across several Ruby code bases, and not all of them are +specific to the GitLab application. +When creating a new cop that could be applied to multiple applications, we encourage you +to add it to our [`gitlab-styles`](https://gitlab.com/gitlab-org/gitlab-styles) gem. +If the cop targets rules that only apply to the main GitLab application, +it should be added to [GitLab](https://gitlab.com/gitlab-org/gitlab) instead. + +## Cop grace period + +A cop is in a _grace period_ if it is enabled and has `Details: grace period` defined in its TODO YAML configuration. + +On the default branch, offenses from cops in the [grace period](rake_tasks.md#run-rubocop-in-graceful-mode) do not fail the RuboCop CI job. Instead, the job notifies the `#f_rubocop` Slack channel. However, on other branches, the RuboCop job fails. + +A grace period can safely be lifted as soon as there are no warnings for 2 weeks in the `#f_rubocop` channel on Slack. + +## Enabling a new cop + +1. Enable the new cop in `.rubocop.yml` (if not already done via [`gitlab-styles`](https://gitlab.com/gitlab-org/ruby/gems/gitlab-styles)). +1. [Generate TODOs for the new cop](rake_tasks.md#generate-initial-rubocop-todo-list). +1. [Set the new cop to `grace period`](#cop-grace-period). +1. Create an issue to fix TODOs and encourage community contributions (via ~"good for new contributors" and/or ~"Seeking community contributions"). [See some examples](https://gitlab.com/gitlab-org/gitlab/-/issues/?sort=created_date&state=opened&label_name%5B%5D=good%20for%20new%20contributors&label_name%5B%5D=static%20code%20analysis&first_page_size=20). +1. Create an issue to remove `grace period` after 2 weeks of silence in the `#f_rubocop` Slack channel. [See an example](https://gitlab.com/gitlab-org/gitlab/-/issues/374903). + +## Silenced offenses + +When offenses are silenced for cops in the [grace period](#cop-grace-period), +the `#f_rubocop` Slack channel receives a notification message every 2 hours. + +To fix this issue: + +1. Find cops with silenced offenses in the linked CI job. +1. [Generate TODOs](rake_tasks.md#generate-initial-rubocop-todo-list) for these cops. + +### RuboCop node pattern + +When creating [node patterns](https://docs.rubocop.org/rubocop-ast/node_pattern.html) to match +Ruby's AST, you can use [`scripts/rubocop-parse`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/scripts/rubocop-parse). +This displays the AST of a Ruby expression to help you create the matcher. +See also [!97024](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/97024). + +## Resolving RuboCop exceptions + +When the number of RuboCop exceptions exceeds the default [`exclude-limit` of 15](https://docs.rubocop.org/rubocop/1.2/usage/basic_usage.html#command-line-flags), +we may want to resolve exceptions over multiple commits. To minimize confusion, +we should track our progress through the exception list. + +The preferred way to [generate the initial list or a list for specific RuboCop rules](rake_tasks.md#generate-initial-rubocop-todo-list) +is to run the Rake task `rubocop:todo:generate`: + +```shell +# Initial list +bundle exec rake rubocop:todo:generate + +# List for specific RuboCop rules +bundle exec rake 'rubocop:todo:generate[Gitlab/NamespacedClass,Lint/Syntax]' +``` + +This Rake task creates or updates the exception list in `.rubocop_todo/`. For +example, the configuration for the RuboCop rule `Gitlab/NamespacedClass` is +located in `.rubocop_todo/gitlab/namespaced_class.yml`. + +Make sure to commit any changes in `.rubocop_todo/` after running the Rake task. + +## Reveal existing RuboCop exceptions + +To reveal existing RuboCop exceptions in the code that have been excluded via `.rubocop_todo.yml` and +`.rubocop_todo/**/*.yml`, set the environment variable `REVEAL_RUBOCOP_TODO` to `1`. + +This allows you to reveal existing RuboCop exceptions during your daily work cycle and fix them along the way. + +NOTE: +Define permanent `Exclude`s in `.rubocop.yml` instead of `.rubocop_todo/**/*.yml`. |