Creating a New Rule

This is a new contributors guide to writing new rules and submitting them as contributions to JSCS:

Feel free to submit a work in progress PR and ask for feedback or help with ASTs or our APIs. It can be difficult when first learning about ASTs but it picks up quickly!

Check out CONTRIBUTING.md as well!

• lib/rules has rules with hyphen separated file names. For example: disallow-anonymous-functions.js. Each rule is accompanied by JS doc style documentation at the beginning which is used on the website, e.g. http://jscs.info/rule/disallowAnonymousFunctions.
• test/specs/rules contains tests for each rule, one per file.
• JSCS uses mocha to run its tests.
• To test out your new rule, type npm test and make sure there are no errors with the tests you wrote (this runs jshint/jscs as well as unit tests).
  • You can also run a specific subset of rules with -g, e.g. mocha -g "disallow-anonymous-functions" or mocha -g "#1831"

Definitely check out the existing rules for conventions/help or look for and older PR that starts with New Rule: newRuleHere. Using a tool like http://astexplorer.net/ is recommended.

• Make a rule implementation like lib/rules/awesome-new-rule.js.
• Register the rule in the registerDefaultRules method of StringChecker (lib/string-checker.js).
  • this.registerRule(require('../rules/awesome-new-rule'));
• Add your rule's tests like test/specs/rules/awesome-new-rule.js
• Add your rule to a group in grouping.json (If you don't know just add it to the last group).