GitHub Flavored Markdown Linting

We are using the markdownlint library (via markdownlint-cli2 and adding our opinions and custom rules to it.

To review behaviors supported by markdownlint, particularly how to enable or disable rules, see markdownlint-cli2 configuration.

Opinions

At GitHub, we have opinions about how our markdown should be written.

In addition to defaults defined by markdownlint, we use this repository to enforce rules not defined by default, including our own custom rules.

See our opinions codified in index.js.

Should I disable rules enabled by this plugin?

This plugin will enable the defaults defined by markdownlint. Several of these pertain to stylistic practices. You may choose to disable these rules if you determine it doesn't provide value for your project.

However, others of these rules should NOT be disabled because they encourage best accessibility practices. Disabling these rules will negatively impact accessibility. These rules are specified in accessibility.json.

Rules

The following are custom rules defined in this plugin.

• GH001 no-default-alt-text
• GH002 no-generic-link-text

See markdownlint rules for documentation on rules pulled in from markdownlint.

Usage

Note: We recommend configuring markdownlint-cli2 over markdownlint-cli for compatibility with the vscode-markdownlint plugin.

1. Create a .markdownlint-cli2.cjs file in the root of your repository

   touch .markdownlint-cli2.cjs

2. Install packages

   • npm install -D markdownlint-cli2 # if updating existing package, check for updates
     npm install -D @github/markdownlint-github [--@github:registry=https://registry.npmjs.org]

3. Add/modify your linting script in package.json.

    markdownlint-cli2 \"**/*.{md,mdx}\" \"!node_modules\"

4. Edit .markdownlint-cli2.cjs file to suit your needs. Start with

   const options = require('@github/markdownlint-github').init()
   module.exports = {
       config: options,
       customRules: ["@github/markdownlint-github"],
   }

   Or, you can also pass in configuration options that you wish to override the default. This looks like:

   const options = require('@github/markdownlint-github').init({
       'fenced-code-language': false,
   })
   module.exports = {
       config: options,
       customRules: ["@github/markdownlint-github"],
   }

5. Install the vscode-markdownlint plugin to ensure markdownlint violations are surfaced in the file. This plugin should flag rules based off your .markdownlint-cli2.cjs configuration. When you make edits to your configuartion, you will need to reload the VSCode window (Ctrl+Shift+P -> Reload Window) to ensure the extension syncs.

Advanced: Adding custom rules in your codebase

You may write custom rules within your repository. Follow the custom rules guide in markdownlint to write your rule.

The rule will need to be enabled in the configuration. For instance, if you introduce some-rule.js with the name "some-rule", you must set the path of the custom rule in the .markdownlint-cli2.cjs file:

module.exports = require('@github/markdownlint-github').init({
    "some-rule": true,
    customRules: ["@github/markdownlint-github", "some-rule.js"],
})

See markdownlint-cli2 configuration.

Consider upstreaming any rules you find useful as proposals to this repository.

Contributing

Please read Contributing Guide for more information.