remark-lint is a markdown code style linter. Another linter? Yes. Ensuring the markdown you (and contributors) write is of great quality will provide better rendering in all the different markdown parsers, and makes sure less refactoring is needed afterwards.

What is quality? That’s up to you, but there are sensible presets.

remark-lint is built on remark, a powerful markdown processor powered by plugins (such as this one).

Table of Contents

• Installation
• Command line
• Programmatic
• Rules
• Configuring remark-lint
• Using remark to fix your markdown
• Editor Integrations
• List of Presets
• List of External Rules
• Related
• License

Installation

npm:

npm install remark-lint

remark-lint is also available as an AMD, CommonJS, and globals module, uncompressed and compressed.

Command line

Use remark-lint together with remark-cli, and a preset.

npm install --save remark-cli remark-lint remark-preset-lint-recommended

Then, configure remark in your package.json:

  // ...
  "scripts": {
    "lint-md": "remark ."
  },
  // ...
  "remarkConfig": {
    "presets": ["lint-recommended"]
  }
  // ...

Let’s say there’s an example.md, which looks as follows:

* Hello

[World][]

Now, running our lint-md script with npm, npm run lint-md, yields:

example.md
       1:3  warning  Incorrect list-item indent: add 2 spaces  list-item-indent
  3:1-3:10  warning  Found reference to undefined definition   no-undefined-references
⚠ 2 warnings

See doc/rules.md for what those warnings are (and how to turn them off).

Programmatic

Use remark-lint together with remark:

npm install remark remark-lint

Let’s say example.js looks as follows:

var report = require('vfile-reporter');
var remark = require('remark');
var lint = require('remark-lint');

var file = remark().use(lint, {
  firstHeadingLevel: true
}).process('## Hello world!');

console.log(report(file));

Now, running node example.js yields:

  1:1-1:16  warning  First heading level should be `1`  first-heading-level

⚠ 1 warning

remark.use(lint[, options])

Adds warnings for style violations to the processed virtual file.

When processing a file, these warnings are available at file.messages, and look as follows:

{ [1:1-1:16: First heading level should be `1`]
  message: 'First heading level should be `1`',
  name: '1:1-1:16',
  file: '',
  reason: 'First heading level should be `1`',
  line: 1,
  column: 1,
  location: {
    start: { line: 1, column: 1, offset: 0 },
    end: { line: 1, column: 16, offset: 15 } },
  fatal: false,
  ruleId: 'first-heading-level',
  source: 'remark-lint' }

See VFileMessage for more information.

Rules

doc/rules.md describes all available rules, what they check for, examples of markdown they warn for, and how to fix their warnings.

Configuring remark-lint

remark-lint is a remark plug-in and supports configuration through its configuration files.

An example .remarkrc file could look as follows:

{
  "presets": ["lint-recommended"],
  "plugins": {
    "lint": {
      "list-item-indent": false
    }
  }
}

Where the object at plugins.lint is a map of ruleIds and their values, which precede over presets.

Using our example.md from before:

* Hello

[World][]

Now, running npm run lint-md yields:

example.md
   3:1-3:10  warning  Found reference to undefined definition   no-undefined-references

⚠ 2 warnings

In addition, you can also provide configuration comments to turn a rule on or off inside a file. Note that you cannot change what a setting, such as maximum-line-length, just whether they are shown or not. Read more about configuration comments in remark-message-controls documentation.

The following file will warn twice for the duplicate headings:

# Hello

## Hello

### Hello

The following file will warn once (the second heading is ignored, but the third is re-enabled):

# Hello

<!--lint disable no-duplicate-headings-->

## Hello

<!--lint enable no-duplicate-headings-->

### Hello

Using remark to fix your markdown

One of remark’s cool parts is that it compiles to very clean, and highly cross-vendor supported markdown. It’ll ensure list items use a single bullet, emphasis and strong use a standard marker, and that your table fences are aligned.

remark should be able to fix most of your styling issues automatically, and I strongly suggest checking out how it can make your life easier 👍

Editor Integrations

Currently, remark-lint is integrated with Atom through linter-markdown.

If you want to run all of remark from Atom, use linter-remark.

To run remark, optionally with remark-lint from Gulp, use gulp-remark.

I’m very interested in more integrations. Let me know if I can help.

List of Presets

Presets can be loaded through the preset setting.

• remark-preset-lint-consistent — Rules that enforce consistency;
• remark-preset-lint-recommended — Rules that prevent mistakes or syntaxes that do not work correctly across vendors.

List of External Rules

External rules can be loaded through the external setting.

Learn how to create and use external rules in doc/external.md.

• vhf/remark-lint-alphabetize-lists — Ensure list items are in alphabetical order;
• vhf/remark-lint-blank-lines-1-0-2 — Ensure a specific number of lines between blocks;
• vhf/remark-lint-books-links — Ensure links in lists of books follow a standard format;
• Qard/remark-lint-code — Lint fenced code blocks by corresponding language tags, currently supporting ESLint.
• vhf/remark-lint-no-empty-sections — Ensure every heading is followed by content (forming a section);
• chcokr/remark-lint-sentence-newline — Ensure sentences are followed by a newline;
• vhf/remark-lint-no-url-trailing-slash — Ensure that the href of links has no trailing slash.

Related

• wooorm/remark-validate-links — Validate if links point to existing headings and files in markdown.

License

MIT © Titus Wormer