remark-lint-no-duplicate-headings-in-section

remark-lint rule to warn when the same text is used in multiple headings in a section.

Contents

• What is this?
• When should I use this?
• Presets
• Install
• Use
• API
  • unified().use(remarkLintNoDuplicateHeadingsInSection)
• Recommendation
• Examples
• Compatibility
• Contribute
• License

What is this?

This package checks that headings are unique in sections.

When should I use this?

You can use this package to check that headings are unique.

Presets

This plugin is not included in presets maintained here.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install remark-lint-no-duplicate-headings-in-section

In Deno with esm.sh:

import remarkLintNoDuplicateHeadingsInSection from 'https://esm.sh/remark-lint-no-duplicate-headings-in-section@4'

In browsers with esm.sh:

<script type="module">
  import remarkLintNoDuplicateHeadingsInSection from 'https://esm.sh/remark-lint-no-duplicate-headings-in-section@4?bundle'
</script>

Use

On the API:

import remarkLint from 'remark-lint'
import remarkLintNoDuplicateHeadingsInSection from 'remark-lint-no-duplicate-headings-in-section'
import remarkParse from 'remark-parse'
import remarkStringify from 'remark-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'
import {reporter} from 'vfile-reporter'

const file = await read('example.md')

await unified()
  .use(remarkParse)
  .use(remarkLint)
  .use(remarkLintNoDuplicateHeadingsInSection)
  .use(remarkStringify)
  .process(file)

console.error(reporter(file))

On the CLI:

remark --frail --use remark-lint --use remark-lint-no-duplicate-headings-in-section .

On the CLI in a config file (here a package.json):

 …
 "remarkConfig": {
   "plugins": [
     …
     "remark-lint",
+    "remark-lint-no-duplicate-headings-in-section",
     …
   ]
 }
 …

API

This package exports no identifiers. It exports no additional TypeScript types. The default export is remarkLintNoDuplicateHeadingsInSection.

unified().use(remarkLintNoDuplicateHeadingsInSection)

Warn when the same text is used in multiple headings in a section.

Parameters

There are no options.

Returns

Transform (Transformer from unified).

Recommendation

It’s likely a mistake that the same heading text is used in the same section.

Examples

ok.md

In

# Planets

## Venus

### Discovery

## Mars

### Discovery

### Phobos

#### Discovery

Out

No messages.

not-ok.md

In

# Planets

## Mars

### Discovery

### Discovery

Out

7:1-7:14: Unexpected heading with equivalent text in section, expected unique headings

tolerant-heading-increment.md

In

# Planets

#### Discovery

###### Phobos

#### Discovery

###### Deimos

Out

7:1-7:15: Unexpected heading with equivalent text in section, expected unique headings

mdx.mdx

In

👉 Note: this example uses MDX (remark-mdx).

MDX is supported <em>too</em>.

<h1>Planets</h1>
<h2>Mars</h2>
<h3>Discovery</h3>
<h3>Discovery</h3>

Out

6:1-6:19: Unexpected heading with equivalent text in section, expected unique headings

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, remark-lint-no-duplicate-headings-in-section@4, compatible with Node.js 16.

Contribute

See contributing.md in remarkjs/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MIT © Titus Wormer