This document outlines the steps required to create your own check, share it, and then use it in your projects.

1. Creating a theme check extension
2. Sharing a theme check extension
3. Using a theme check extension

Each theme check extension is an npm module with a name in the format theme-check-<extension-name>, such as theme-check-preact. You can also use scoped packages in the format @<scope>/theme-check-<extension-name>, such as @acme/theme-check-extension.

The name property in your package.json should fit the naming convention described in the Naming your extension section.

The main entry of your project's package.json is assumed to have a checks export containing all the checks provided by your extension:

// dist/index.js
const MyFirstNewCheck = require('./checks/MyFirstNewCheck');
const MySecondNewCheck = require('./checks/MySecondNewCheck');

exports.checks = [
  MyFirstNewCheck,
  MySecondNewCheck,
];

Here's a package.json example that would use dist/index.js as its main entry:

{
  "name": "@acme/theme-check-extension",
  "description": "Custom checks that we use",
  "main": "dist/index.js",
  "dependencies": {
    "...": "..."
  },
}

You may want to offer recommended configurations along with your checks to make it easy for users to use them.

For this, you can add any number of .yml files to your published package.

For instance, you may add a recommended.yml file at the root of your package:

# In your extension's $root/recommended.yml file
MyFirstNewCheck:
  enabled: true
  severity: 0
MySecondNewCheck:
  enabled: true
  severity: 1
  someConfigValue: 100

Users can extend this configuration directly instead of providing configuration for each check.

# In a user's `.theme-check.yml`
extends:
  - 'theme-check:recommended'
  - '@acme/theme-check-extension/recommended.yml'

Note: the .yml extension is required.

For a detailed explanation, see the Using it in your projects section.

To make it available for others to use, you can publish your extension to npm.

1. Add your theme check extension as a dependency of your project.

   npm install -D @acme/theme-check-extension

2. Reference or extend a config provided by your extension.

   extends:
     - 'theme-check:recommended'
     - '@acme/theme-check-extension/recommended.yml'
   MyNonRecommendedCheck:
     enabled: true
     severity: suggestion