# remark-lint-file-extension [![Build][badge-build-image]][badge-build-url] [![Coverage][badge-coverage-image]][badge-coverage-url] [![Downloads][badge-downloads-image]][badge-downloads-url] [![Size][badge-size-image]][badge-size-url] [![Sponsors][badge-funding-sponsors-image]][badge-funding-url] [![Backers][badge-funding-backers-image]][badge-funding-url] [![Chat][badge-chat-image]][badge-chat-url] [`remark-lint`][github-remark-lint] rule to warn for unexpected file extensions. ## Contents * [What is this?](#what-is-this) * [When should I use this?](#when-should-i-use-this) * [Presets](#presets) * [Install](#install) * [Use](#use) * [API](#api) * [`unified().use(remarkLintFileExtension[, options])`](#unifieduseremarklintfileextension-options) * [`Extensions`](#extensions) * [`Options`](#options) * [Recommendation](#recommendation) * [Examples](#examples) * [Compatibility](#compatibility) * [Contribute](#contribute) * [License](#license) ## What is this? This package checks the file extension. ## When should I use this? You can use this package to check that file extensions are consistent. ## Presets This plugin is included in the following presets: | Preset | Options | | - | - | | [`remark-preset-lint-markdown-style-guide`](https://github.com/remarkjs/remark-lint/tree/main/packages/remark-preset-lint-markdown-style-guide) | `'md'` | ## Install This package is [ESM only][github-gist-esm]. In Node.js (version 16+), install with [npm][npm-install]: ```sh npm install remark-lint-file-extension ``` In Deno with [`esm.sh`][esm-sh]: ```js import remarkLintFileExtension from 'https://esm.sh/remark-lint-file-extension@3' ``` In browsers with [`esm.sh`][esm-sh]: ```html ``` ## Use On the API: ```js import remarkLint from 'remark-lint' import remarkLintFileExtension from 'remark-lint-file-extension' 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(remarkLintFileExtension) .use(remarkStringify) .process(file) console.error(reporter(file)) ``` On the CLI: ```sh remark --frail --use remark-lint --use remark-lint-file-extension . ``` On the CLI in a config file (here a `package.json`): ```diff … "remarkConfig": { "plugins": [ … "remark-lint", + "remark-lint-file-extension", … ] } … ``` ## API This package exports no identifiers. It exports the [TypeScript][typescript] types [`Extensions`][api-extensions] and [`Options`][api-options]. The default export is [`remarkLintFileExtension`][api-remark-lint-file-extension]. ### `unified().use(remarkLintFileExtension[, options])` Warn for unexpected extensions. ###### Parameters * `options` ([`Extensions`][api-extensions] or [`Options`][api-options], optional) — configuration ###### Returns Transform ([`Transformer` from `unified`][github-unified-transformer]). ### `Extensions` File extension(s) (TypeScript type). ###### Type ```ts type Extensions = Array | string ``` ### `Options` Configuration (TypeScript type). ###### Fields * `allowExtensionless` (`boolean`, default: `true`) — allow no file extension such as `AUTHORS` or `LICENSE` * `extensions` ([`Extensions`][api-extensions], default: `['mdx', 'md']`) — allowed file extension(s) ## Recommendation Use `md` as it’s the most common. Also use `md` when your markdown contains common syntax extensions (such as GFM, frontmatter, or math). Do not use `md` for MDX: use `mdx` instead. ## Examples ##### `readme.md` ###### Out No messages. ##### `readme.mdx` ###### Out No messages. ##### `readme` ###### Out No messages. ##### `readme` When configured with `{ allowExtensionless: false }`. ###### Out ```text 1:1: Unexpected missing file extension, expected `mdx` or `md` ``` ##### `readme.mkd` ###### Out ```text 1:1: Unexpected file extension `mkd`, expected `mdx` or `md` ``` ##### `readme.mkd` When configured with `'mkd'`. ###### Out No messages. ##### `readme.css` When configured with `[ 'markdown', 'md', 'mdown', 'mdwn', 'mdx', 'mkd', 'mkdn', 'mkdown', 'ron' ]`. ###### Out ```text 1:1: Unexpected file extension `css`, expected `markdown`, `md`, `mdown`, … ``` ## 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-file-extension@3`, 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-extensions]: #extensions [api-options]: #options [api-remark-lint-file-extension]: #unifieduseremarklintfileextension-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-file-extension.svg [badge-downloads-url]: https://www.npmjs.com/package/remark-lint-file-extension [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-file-extension [badge-size-url]: https://bundlejs.com/?q=remark-lint-file-extension [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-unified-transformer]: https://github.com/unifiedjs/unified#transformer [npm-install]: https://docs.npmjs.com/cli/install [typescript]: https://www.typescriptlang.org