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wooorm committed May 22, 2022
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[![Backers][backers-badge]][collective]
[![Chat][chat-badge]][chat]

Extension for [`mdast-util-from-markdown`][from-markdown] and/or
[`mdast-util-to-markdown`][to-markdown] to support MDX.js ESM import/exports.
When parsing (`from-markdown`), must be combined with
[`micromark-extension-mdxjs-esm`][extension].

This utility handles parsing and serializing.
See [`micromark-extension-mdxjs-esm`][extension] for how the syntax works.
[mdast][] extensions to parse and serialize [MDX][] ESM import/exports.

## Contents

* [What is this?](#what-is-this)
* [When to use this](#when-to-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`mdxjsEsmFromMarkdown`](#mdxjsesmfrommarkdown)
* [`mdxjsEsmToMarkdown`](#mdxjsesmtomarkdown)
* [Syntax tree](#syntax-tree)
* [Nodes](#nodes)
* [Content model](#content-model)
* [Types](#types)
* [Compatibility](#compatibility)
* [Related](#related)
* [Contribute](#contribute)
* [License](#license)

## What is this?

This package contains extensions that add support for the ESM syntax enabled
by MDX to [`mdast-util-from-markdown`][mdast-util-from-markdown] and
[`mdast-util-to-markdown`][mdast-util-to-markdown].

## When to use this

Use [`mdast-util-mdx`][mdast-util-mdx] if you want all of MDX / MDX.js.
Use this otherwise.
These tools are all rather low-level.
In most cases, you’d want to use [`remark-mdx`][remark-mdx] with remark instead.

## Install
When you are working with syntax trees and want all of MDX, use
[`mdast-util-mdx`][mdast-util-mdx] instead.

When working with `mdast-util-from-markdown`, you must combine this package with
[`micromark-extension-mdxjs-esm`][extension].

This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
## Install

[npm][]:
This package is [ESM only][esm].
In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:

```sh
npm install mdast-util-mdxjs-esm
```

In Deno with [`esm.sh`][esmsh]:

```js
import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from 'https://esm.sh/mdast-util-mdxjs-esm@1'
```

In browsers with [`esm.sh`][esmsh]:

```html
<script type="module">
import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from 'https://esm.sh/mdast-util-mdxjs-esm@1?bundle'
</script>
```

## Use

Say we have an MDX.js file, `example.mdx`:
Say our document `example.mdx` contains:

```mdx
import a from 'b'
export var c = ''
export const c = ''

d
```

And our module, `example.js`, looks as follows:
…and our module `example.js` looks as follows:

```js
import fs from 'fs'
import fs from 'node:fs/promises'
import * as acorn from 'acorn'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {toMarkdown} from 'mdast-util-to-markdown'
import {mdxjsEsm} from 'micromark-extension-mdxjs-esm'
import {mdxjsEsmFromMarkdown, mdxjsEsmToMarkdown} from 'mdast-util-mdxjs-esm'

const doc = fs.readFileSync('example.mdx')
const doc = await fs.readFile('example.mdx')

const tree = fromMarkdown(doc, {
extensions: [mdxjsEsm({acorn, addResult: true})],
Expand All @@ -67,15 +103,15 @@ const out = toMarkdown(tree, {extensions: [mdxjsEsmToMarkdown]})
console.log(out)
```

Now, running `node example` yields (positional info removed for brevity):
…now running `node example.js` yields (positional info removed for brevity):

```js
{
type: 'root',
children: [
{
type: 'mdxjsEsm',
value: "import a from 'b'\nexport var c = ''",
value: "import a from 'b'\nexport const c = ''",
data: {
estree: {
type: 'Program',
Expand All @@ -101,7 +137,7 @@ Now, running `node example` yields (positional info removed for brevity):
init: {type: 'Literal', value: '', raw: "''"}
}
],
kind: 'var'
kind: 'const'
},
specifiers: [],
source: null
Expand All @@ -118,28 +154,27 @@ Now, running `node example` yields (positional info removed for brevity):

```markdown
import a from 'b'
export var c = ''
export const c = ''

d
```

## API

This package exports the following identifier: `mdxjsEsmFromMarkdown`,
This package exports the identifiers `mdxjsEsmFromMarkdown` and
`mdxjsEsmToMarkdown`.
There is no default export.

### `mdxjsEsmFromMarkdown`

### `mdxjsEsmToMarkdown`

Support MDX.js ESM import/exports.
The exports are extensions, respectively for
[`mdast-util-from-markdown`][from-markdown] and
[`mdast-util-to-markdown`][to-markdown].
Extension for [`mdast-util-from-markdown`][mdast-util-from-markdown].

When using the [syntax extension with `addResult`][extension], nodes will have
a `data.estree` field set to an [ESTree][]
a `data.estree` field set to an [ESTree][].

### `mdxjsEsmToMarkdown`

Extension for [`mdast-util-to-markdown`][mdast-util-to-markdown].

## Syntax tree

Expand Down Expand Up @@ -186,27 +221,53 @@ type FlowContentMdxjsEsm = MDXJSEsm | FlowContent
Note that when ESM is present, it can only exist as top-level content: if it has
a *[parent][dfn-parent]*, that parent must be **[Root][dfn-root]**.

## Types

This package is fully typed with [TypeScript][].
It exports the additional type `MdxjsEsm`.

It also registers the node types with `@types/mdast`.
If you’re working with the syntax tree, make sure to import this utility
somewhere in your types, as that registers the new node types in the tree.

```js
/**
* @typedef {import('mdast-util-mdxjs-esm')}
*/

import {visit} from 'unist-util-visit'

/** @type {import('mdast').Root} */
const tree = getMdastNodeSomeHow()

visit(tree, (node) => {
// `node` can now be an ESM node.
})
```

## Compatibility

Projects maintained by the unified collective are compatible with all maintained
versions of Node.js.
As of now, that is Node.js 12.20+, 14.14+, and 16.0+.
Our projects sometimes work with older versions, but this is not guaranteed.

This plugin works with `mdast-util-from-markdown` version 1+ and
`mdast-util-to-markdown` version 1+.

## Related

* [`remarkjs/remark`][remark]
— markdown processor powered by plugins
* [`remarkjs/remark-mdx`][remark-mdx]
— remark plugin to support MDX
* [`syntax-tree/mdast-util-from-markdown`][from-markdown]
— mdast parser using `micromark` to create mdast from markdown
* [`syntax-tree/mdast-util-to-markdown`][to-markdown]
— mdast serializer to create markdown from mdast
* [`syntax-tree/mdast-util-mdx`][mdast-util-mdx]
— mdast utility to support MDX
* [`micromark/micromark`][micromark]
— the smallest commonmark-compliant markdown parser that exists
* [`micromark/micromark-extension-mdxjs-esm`][extension]
— micromark extension to parse MDX.js ESM

## Contribute

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

This project has a [code of conduct][coc].
Expand Down Expand Up @@ -247,30 +308,34 @@ abide by its terms.

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

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

[esmsh]: https://esm.sh

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

[license]: license

[author]: https://wooorm.com

[contributing]: https://github.com/syntax-tree/.github/blob/HEAD/contributing.md
[health]: https://github.com/syntax-tree/.github

[support]: https://github.com/syntax-tree/.github/blob/HEAD/support.md
[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md

[coc]: https://github.com/syntax-tree/.github/blob/HEAD/code-of-conduct.md
[support]: https://github.com/syntax-tree/.github/blob/main/support.md

[mdast]: https://github.com/syntax-tree/mdast
[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md

[remark]: https://github.com/remarkjs/remark
[mdast]: https://github.com/syntax-tree/mdast

[from-markdown]: https://github.com/syntax-tree/mdast-util-from-markdown
[mdast-util-from-markdown]: https://github.com/syntax-tree/mdast-util-from-markdown

[to-markdown]: https://github.com/syntax-tree/mdast-util-to-markdown
[mdast-util-to-markdown]: https://github.com/syntax-tree/mdast-util-to-markdown

[micromark]: https://github.com/micromark/micromark
[mdast-util-mdx]: https://github.com/syntax-tree/mdast-util-mdx

[extension]: https://github.com/micromark/micromark-extension-mdxjs-esm

[mdast-util-mdx]: https://github.com/syntax-tree/mdast-util-mdx

[estree]: https://github.com/estree/estree

[dfn-literal]: https://github.com/syntax-tree/mdast#literal
Expand All @@ -281,4 +346,6 @@ abide by its terms.

[dfn-flow-content]: #flowcontent-mdxjs-esm

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

[mdx]: https://mdxjs.com

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