remark-lint-no-multiple-toplevel-headings

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[remark-lint][github-remark-lint] rule to warn when top-level headings are used multiple times.

Contents

* What is this?
* When should I use this?
* Presets
* Install
* Use
* API
* [unified().use(remarkLintNoMultipleToplevelHeadings[, options])](#unifieduseremarklintnomultipletoplevelheadings-options)
* Depth
* Options
* Recommendation
* Examples
* Compatibility
* Contribute
* License

What is this?

This package checks that top-level headings are unique.

When should I use this?

You can use this package to check heading structure.

Presets

This plugin is included in the following presets:

| Preset | Options |
| - | - |
| remark-preset-lint-markdown-style-guide | |

Install

This package is [ESM only][github-gist-esm].
In Node.js (version 16+),
install with [npm][npm-install]:

``sh
npm install remark-lint-no-multiple-toplevel-headings
`

In Deno with [esm.sh][esm-sh]:

`js
import remarkLintNoMultipleToplevelHeadings from 'https://esm.sh/remark-lint-no-multiple-toplevel-headings@4'
`

In browsers with [esm.sh][esm-sh]:

`html

`

Use

On the API:

`js
import remarkLint from 'remark-lint'
import remarkLintNoMultipleToplevelHeadings from 'remark-lint-no-multiple-toplevel-headings'
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(remarkLintNoMultipleToplevelHeadings)
.use(remarkStringify)
.process(file)

console.error(reporter(file))
`

On the CLI:

`sh
remark --frail --use remark-lint --use remark-lint-no-multiple-toplevel-headings .
`

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

`diff
…
"remarkConfig": {
"plugins": [
…
"remark-lint",
+ "remark-lint-no-multiple-toplevel-headings",
…
]
}
…
`

API

This package exports no identifiers.
It exports the [TypeScript][typescript] types
[Depth][api-depth] and
[Options][api-options].
The default export is
[remarkLintNoMultipleToplevelHeadings][api-remark-lint-no-multiple-toplevel-headings].

$3

Warn when top-level headings are used multiple times.

###### Parameters

* options ([Options][api-options], default: 1)
— configuration

###### Returns

Transform ([Transformer from unified][github-unified-transformer]).

$3

Depth (TypeScript type).

###### Type

`ts
type Depth = 1 | 2 | 3 | 4 | 5 | 6
`

$3

Configuration (TypeScript type).

###### Type

`ts
type Options = Depth
`

Recommendation

Documents should almost always have one main heading,
which is typically a heading with a rank of 1.

Examples

##### ok.md

###### In

`markdown


Mercury

Venus


`

###### Out

No messages.

##### not-ok.md

###### In

`markdown


Venus

Mercury


`

###### Out

`text
3:1-3:10: Unexpected duplicate toplevel heading, exected a single heading with rank 1
`

##### not-ok.md

When configured with 2.

###### In

`markdown


Venus

Mercury


`

###### Out

`text
3:1-3:11: Unexpected duplicate toplevel heading, exected a single heading with rank 2
`

##### html.md

###### In

`markdown
Venus and mercury.

Earth

Mars


`

###### Out

`text
5:1-5:14: Unexpected duplicate toplevel heading, exected a single heading with rank 1
`

##### mdx.mdx

###### In

> 👉 Note: this example uses
> MDX ([remark-mdx][github-remark-mdx]).

`mdx
Venus and mercury.

Earth

Mars

`

###### Out

`text
4:1-4:14: Unexpected duplicate toplevel heading, exected a single heading with rank 1
`

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-multiple-toplevel-headings@4,
compatible with Node.js 16.

Contribute

See [contributing.md][github-dotfiles-contributing] in [remarkjs/.github][github-dotfiles-health] for ways
to get started.
See [support.md`][github-dotfiles-support] for ways to get help.

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

License

[MIT][file-license] © [Titus Wormer][author]

[api-depth]: #depth

[api-options]: #options

[api-remark-lint-no-multiple-toplevel-headings]: #unifieduseremarklintnomultipletoplevelheadings-options

[author]: https://wooorm.com

[badge-build-image]: https://github.com/remarkjs/remark-lint/workflows/main/badge.svg

[badge-build-url]: https://github.com/remarkjs/remark-lint/actions

[badge-chat-image]: https://img.shields.io/badge/chat-discussions-success.svg

[badge-chat-url]: https://github.com/remarkjs/remark/discussions

[badge-coverage-image]: https://img.shields.io/codecov/c/github/remarkjs/remark-lint.svg

[badge-coverage-url]: https://codecov.io/github/remarkjs/remark-lint

[badge-downloads-image]: https://img.shields.io/npm/dm/remark-lint-no-multiple-toplevel-headings.svg

[badge-downloads-url]: https://www.npmjs.com/package/remark-lint-no-multiple-toplevel-headings

[badge-funding-backers-image]: https://opencollective.com/unified/backers/badge.svg

[badge-funding-sponsors-image]: https://opencollective.com/unified/sponsors/badge.svg

[badge-funding-url]: https://opencollective.com/unified

[badge-size-image]: https://img.shields.io/bundlejs/size/remark-lint-no-multiple-toplevel-headings

[badge-size-url]: https://bundlejs.com/?q=remark-lint-no-multiple-toplevel-headings

[esm-sh]: https://esm.sh

[file-license]: https://github.com/remarkjs/remark-lint/blob/main/license

[github-dotfiles-coc]: https://github.com/remarkjs/.github/blob/main/code-of-conduct.md

[github-dotfiles-contributing]: https://github.com/remarkjs/.github/blob/main/contributing.md

[github-dotfiles-health]: https://github.com/remarkjs/.github

[github-dotfiles-support]: https://github.com/remarkjs/.github/blob/main/support.md

[github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[github-remark-lint]: https://github.com/remarkjs/remark-lint

[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/

[github-unified-transformer]: https://github.com/unifiedjs/unified#transformer

[npm-install]: https://docs.npmjs.com/cli/install

[typescript]: https://www.typescriptlang.org