import {Note} from '../_component/note.server.js'
export const navExclude = true
export const info = {
  author: [
    {name: 'Titus Wormer', github: 'wooorm', twitter: 'wooorm'}
  ],
  published: new Date('2021-11-01'),
  modified: new Date('2021-11-01')
}

<Note type="important">
  **Note**: V2 is around the corner.
  This website is for that.
  It hasn’t been released yet.
  But you can try out the RC.
  You can be of great help by reading through these docs and letting us know
  what’s confusing or wrong or other suggestions you have.
  See [§ Support][support] for where to ask questions and
  [§ Contribute][contribute] for how to help.
</Note>

<Note type="info">
  **Note**: Please let us know of any required changes that aren’t mentioned
  here.
</Note>

# Migrating from v1 to v2

## Contents

*   [ESM](#esm)
*   [Update `@mdx-js/*` packages](#update-mdx-js-packages)
    *   [`@mdx-js/loader`](#mdx-jsloader)
    *   [`@mdx-js/react`, `@mdx-js/preact`, `@mdx-js/vue`](#mdx-jsreact-mdx-jspreact-mdx-jsvue)
    *   [`@mdx-js/mdx`](#mdx-jsmdx)
    *   [`@mdx-js/runtime`](#mdx-jsruntime)
    *   [`remark-mdx`](#remark-mdx)
    *   [`@mdx-js/vue-loader`](#mdx-jsvue-loader)
    *   [`@mdx-js/parcel-plugin-mdx`](#mdx-jsparcel-plugin-mdx)
    *   [Other packages](#other-packages)
*   [Update MDX files](#update-mdx-files)
    *   [JSX](#jsx)
    *   [Expressions](#expressions)
    *   [ESM](#esm-1)
    *   [Markdown](#markdown)
    *   [GFM](#gfm)
*   [Update MDX content](#update-mdx-content)

## ESM

When upgrading to version 2, you might run into import problems.
Our packages are now ESM only.
You have to load them with `import foo from 'foo'` instead of
`const foo = require('foo')`.
Please see [¶ ESM in § Troubleshooting MDX][trouble-esm].

## Update `@mdx-js/*` packages

If you’re experiencing problems, please see [§ Troubleshooting MDX][trouble]
for common errors and how to solve them.

### `@mdx-js/loader`

To update our webpack loader `@mdx-js/loader`, please first update to recent
versions of webpack and React.
Then make sure ESM is supported.
[ESM is explained above][esm].
If you’re having trouble using ESM in your webpack config, here’s an example
that works with our previous `@mdx-js/loader` (`1.6.22`):

<details>
  <summary>Expand example of a `webpack.config.js` in ESM</summary>

  ```js path="webpack.config.js"
  import {URL, fileURLToPath} from 'node:url'
  import webpack from 'webpack'

  const config = {
    mode: 'none',
    context: fileURLToPath(new URL('src/', import.meta.url)),
    entry: ['./index.js'],
    output: {
      path: fileURLToPath(new URL('dest/', import.meta.url)),
      filename: 'bundle.js'
    },
    module: {
      rules: [
        {
          test: /\.mdx?$/,
          use: [
            {
              loader: 'babel-loader',
              options: {presets: ['@babel/preset-env', '@babel/preset-react']}
            },
            {
              loader: '@mdx-js/loader',
              options: {}
            }
          ]
        }
      ]
    }
  };

  export default config
  ```
</details>

Then install MDX version 2:

```sh
npm install @mdx-js/loader@next @mdx-js/react@next remark-gfm
```

You can update your code as follows:

<div className="big-columns">
  <div>
    ```js path="webpack.config.v1.js"
    // …
    {
      test: /\.mdx?$/,
      use: [
        {
          loader: 'babel-loader',
          options: {
            presets: [
              '@babel/preset-env',
              '@babel/preset-react'
            ]
          }
        },
        {
          loader: '@mdx-js/loader',
          options: {}
        }
      ]
    }
    // …
    ```
  </div>

  <div>
    ```js path="webpack.config.v2.js"
    import remarkGfm from 'remark-gfm'

    // …
    {
      test: /\.mdx?$/,
      use: [
        {
          loader: 'babel-loader',
          options: {
            presets: [
              '@babel/preset-env'
            ]
          }
        },
        {
          loader: '@mdx-js/loader',
          options: {
            providerImportSource: '@mdx-js/react',
            remarkPlugins: [remarkGfm]
          }
        }
      ]
    }
    // …
    ```
  </div>
</div>

<Note type="info">
  **Note**: getting an error `ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`?
  See [this note on `webpack-cli`](/packages/loader/#note-webpack-cli).
</Note>

The above changes get MDX 2 close to how MDX 1 worked.
You can make it simpler:

*   [`babel-loader`][babel-loader] is optional.
    It compiles modern JavaScript to JavaScript your users support.
    If you don’t need that you can remove it before `@mdx-js/loader`
*   [`remark-gfm`][remark-gfm] is optional.
    It adds support for autolink literals, footnotes, strikethrough, tables, and
    task lists.
    If you don’t want them, you can uninstall it, remove the import, and remove
    it from `options.remarkPlugins`.
    More info in [our guide on GFM][guide-gfm]
*   [`@mdx-js/react`][mdx-react] is optional.
    It adds support for context based components passing.
    If you don’t need that, you can uninstall it and remove
    `options.providerImportSource`.
    More info in [¶ MDX provider in § Using MDX][mdx-provider]

`@mdx-js/loader` now supports Preact and other JSX runtimes through
configuration.
Using Preact as an example:

```js path="webpack.config.v2-preact.js"
// …
{
  loader: '@mdx-js/loader',
  options: {
    jsxImportSource: 'preact',
    // Optional: either remove the following line or install `@mdx-js/preact`.
    providerImportSource: '@mdx-js/preact'
  }
}
// …
```

For more information, please see [§ API in `@mdx-js/loader`][loader-api].

###### Changes

The options accepted by the loader changed:

*   `renderer` is replaced by
    [`options.jsxImportSource`][mdx-options-jsximportsource],
    [`options.providerImportSource`][mdx-options-providerimportsource],
    and others options.
    More info in [§ API in `@mdx-js/mdx`][mdx-api]
*   Other options were undocumented but passed to `@mdx-js/mdx`.
    See `@mdx-js/mdx` below if needed

For more information, please see [§ API in `@mdx-js/loader`][loader-api].

### `@mdx-js/react`, `@mdx-js/preact`, `@mdx-js/vue`

To update our framework integrations, please first update to recent versions of
React, Preact, or Vue 3.
Then make sure ESM is supported.
[ESM is explained above][esm].
Then install version 2:

```sh
npm install @mdx-js/react@next # Change `react` to `preact` or `vue` if needed
```

Note that these packages now only add support for context based components
passing.
If you don’t need that, you can uninstall them.
More info in [¶ MDX provider in § Using MDX][mdx-provider].

###### Changes

The interface of changed slightly:

*   The named export `mdx`, which was a `createElement` function, is removed.
    You can use your framework’s functions instead: `React.createElement`,
    `h` from `preact`, etc.

### `@mdx-js/mdx`

To update our core compiler `@mdx-js/mdx`, first make sure ESM is supported.
[ESM is explained above][esm].
Then install version 2:

```sh
npm install @mdx-js/mdx@next @mdx-js/react@next remark-gfm
```

You can update your code as follows:

<div className="big-columns">
  <div>
    ```js path="v1.js"
    import mdx from '@mdx-js/mdx'

    const result = await mdx('# hi')

    console.log(result)
    ```
  </div>

  <div>
    ```js path="v2.js"
    import {compile} from '@mdx-js/mdx'
    import remarkGfm from 'remark-gfm'

    const result = await compile('# hi', {
      providerImportSource: '@mdx-js/react',
      remarkPlugins: [remarkGfm]
    })

    console.log(String(result))
    ```
  </div>
</div>

The above changes get MDX 2 close to how MDX 1 worked.
You can make it simpler:

*   [`remark-gfm`][remark-gfm] is optional.
    It adds support for autolink literals, footnotes, strikethrough, tables, and
    task lists.
    If you don’t want them, you can uninstall it, remove the import, and remove
    it from `options.remarkPlugins`.
    More info in [our guide on GFM][guide-gfm]
*   [`@mdx-js/react`][mdx-react] is optional.
    It adds support for context based components passing.
    If you don’t need that, you can uninstall it and remove
    `options.providerImportSource`.
    More info in [¶ MDX provider in § Using MDX][mdx-provider]

`@mdx-js/mdx` now supports Preact and other JSX runtimes through configuration.
Using Preact as an example:

```js path="v2-preact.js"
import {compile} from '@mdx-js/mdx'

const result = await compile('# hi', {jsxImportSource: 'preact'})
```

For more information, please see [§ API in `@mdx-js/mdx`][mdx-api]

###### Changes

The interface of `@mdx-js/mdx` changed:

*   The default export is replaced by the named export [`compile`][mdx-compile]
*   The named export `sync` is replaced by [`compileSync`][mdx-compilesync]
*   The named export `createCompiler` is replaced by
    [`createProcessor`][mdx-createprocessor]
*   The named export `createMdxAstCompiler` is removed, use `remark` with
    `remark-mdx` instead
*   The return value of `compile`, `compileSync` are now [VFile][]s instead of
    strings
*   There are new exports [`evaluate`][mdx-evaluate],
    [`evaluateSync`][mdx-evaluatesync] to eval (compile and run) MDX

Options in version 1 were undocumented.
If you used them:

*   `filepath` is replaced by accepting a VFile or compatible object as the
    first argument [`file`][mdx-file]
*   `compilers` is replaced by
    [`options.recmaPlugins`][mdx-options-recmaplugins]
*   `hastPlugins` is replaced by
    [`options.rehypePlugins`][mdx-options-rehypeplugins]
*   `mdPlugins` is replaced by
    [`options.remarkPlugins`][mdx-options-remarkplugins]
*   `skipExport` is removed, [`evaluate`][mdx-evaluate] can do this
    automatically
*   `wrapExport` is removed, use a custom recma plugin instead
*   There are many new options to support different JSX runtimes, non-React JSX,
    compile JSX away, source maps, normal markdown, and otherwise change how MDX
    is compiled

For more information, please see [§ API in `@mdx-js/mdx`][mdx-api].

### `@mdx-js/runtime`

We’ve deprecated `@mdx-js/runtime`.
Our core compiler `@mdx-js/mdx` can now do the same and more.
To update, first make sure ESM is supported.
[ESM is explained above][esm].
Please also make sure you are using a recent version of React.
Then uninstall `@mdx-js/runtime` and install `@mdx-js/mdx` and `@mdx-js/react`:

```sh
npm uninstall @mdx-js/runtime
npm install @mdx-js/mdx@next @mdx-js/react@next
```

You can update your code as follows:

<div className="big-columns">
  <div>
    ```js path="v1.js"
    import MDX from '@mdx-js/runtime'

    const components = {/* … */}
    const value = '# hi'

    export default () => (
      <MDX components={components}>
        {value}
      </MDX>
    )
    ```
  </div>

  <div>
    ```js path="v2.js"
    import * as runtime from 'react/jsx-runtime.js'
    import * as provider from '@mdx-js/react'
    import {evaluate} from '@mdx-js/mdx'

    const components = {/* … */}
    const value = '# hi'
    const {default: Content} = await evaluate(value, {...provider, ...runtime})

    export default () => (
      <Content components={components} />
    )
    ```
  </div>
</div>

The above changes get MDX 2 close to how MDX 1 worked.
You can make it simpler:

*   [`@mdx-js/react`][mdx-react] is optional.
    It adds support for context based components passing.
    If you don’t need that, you can uninstall it and remove
    `options.providerImportSource`.
    More info in [¶ MDX provider in § Using MDX][mdx-provider]

`@mdx-js/mdx` now supports Preact and other JSX runtimes through configuration.
Using Emotion as an example:

```js path="v2-emotion.js"
// …
import * as runtime from '@emotion/react/jsx-runtime.js'
// …
```

For more information, please see [`evaluate` in `@mdx-js/mdx`][mdx-evaluate].

###### Changes

*   The package `@mdx-js/runtime` is replaced by [`evaluate`][mdx-evaluate]
    from `@mdx-js/mdx`
*   `evaluate` supports any JSX runtime and providers are optional
*   `evaluate` yields an `MDXContent` component just like how importing
    and MDX file works
*   `evaluate` supports imports and exports inside evaluated MDX

For more information, please see [`evaluate` in `@mdx-js/mdx`][mdx-evaluate].

### `remark-mdx`

To update our remark plugin `remark-mdx`, first make sure ESM is supported.
[ESM is explained above][esm].
Then install version 2:

```sh
npm install remark-mdx@next
```

For more information, please see [§ Use in `remark-mdx`][remark-mdx-use].

### `@mdx-js/vue-loader`

We’ve deprecated `@mdx-js/vue-loader`.
Our main loader `@mdx-js/loader` can now do the same and more.
To update, first remove `@mdx-js/vue-loader` and upgrade to Vue 3.
Then, see [¶ Vue in § Getting started](/docs/getting-started/#vue) on how to use
Vue with MDX.

### `@mdx-js/parcel-plugin-mdx`

We’ve deprecated `@mdx-js/parcel-plugin-mdx`.
Parcel 2 has their own plugin.
To update, first remove `@mdx-js/parcel-plugin-mdx` and upgrade to Parcel 2.
Then, see [¶ Parcel in § Getting started](/docs/getting-started/#parcel) on how
to use Parcel with MDX.

### Other packages

We removed several packages doing internal work for us.
These packages are:

*   `@mdx-js/util`
    — no longer needed internal helpers
*   `@mdx-js/test-util`
    — no longer needed test helpers, `evaluate` can do them
*   `gatsby-theme-mdx`
    — no longer needed website template
*   `remark-mdx-remove-imports`, `babel-plugin-extract-import-names`
    — no longer needed transforms, our compiler handles imports
*   `remark-mdx-remove-exports`, `babel-plugin-remove-export-keywords`
    — no longer needed transforms, our compiler handles exports
*   `babel-plugin-html-attributes-to-jsx`
    — no longer needed transform, something similar is done by
    [`hast-util-to-estree`](https://github.com/syntax-tree/hast-util-to-estree)
*   `babel-plugin-apply-mdx-type-props`
    — no longer needed transform due to the new architecture
*   `create-mdx`
    — no longer needed, we recommend to start your project with whatever other
    integrations you prefer and *then* add MDX to it

## Update MDX files

Now you’ve updated our packages, you can update your MDX files.
In version 2, we improved the syntax of the MDX format.
When upgrading, you’ll likely get errors.
Read those error messages carefully, as they typically explain what
happened where and how to fix it.
See [§ Troubleshooting MDX][trouble] for common errors and how to solve them.

### JSX

Let’s kick off with a couple of things that are now possible with JSX in MDX.
You don’t need blank lines between JSX and markdown anymore:

```html language="mdx" chrome=no
<hgroup>
# This is a heading now
</hgroup>
```

You can now indent your JSX and markdown:

````html language="mdx" chrome=no
<article>
  <hgroup>
    # This is a heading now, not code or plain text
  </hgroup>
  <section>
    ```js
    // if you do want code blocks, use fenced code
    ```
  </section>
</article>
````

You can use markdown “inlines” but not “blocks” inside JSX if the text and tags
are on the same line:

```html language="mdx" chrome=no
<div># this is not a heading but *this* is emphasis</div>
```

Text and tags on one line don’t produce blocks so they don’t produce `<p>`s
either.
On separate lines, they do:

```html language="mdx" chrome=no
<div>
  This is a `p`.
</div>
```

We differentiate using this rule (same line or not).
Not based on semantics of elements in HTML.
So you *can* build incorrect HTML (which you shouldn’t):

```html language="mdx" chrome=no
<h1 className="main">
  Don’t do this: it’s a `p` in an `h1`
</h1>

<h1 className="main">Do this: an `h1` with `code`</h1>
```

It’s not possible to wrap “blocks” if text and tags are on the same line but the
corresponding tags are on different lines:

```html language="mdx" chrome=no
Welcome! <a href="about.html">

This is home of...

# The Falcons!</a>
```

That’s because to parse markdown, we first have to divide it into “blocks”.
So in this case two paragraphs and a heading.
Leaving an opening `a` tag in the first paragraph and a stray closing `a` tag in
the heading.

We also fixed several cases where JSX was not parsed or handled correctly or
even crashed.
More on JSX in MDX is in [¶ JSX in § What is MDX?][what-jsx]

### Expressions

You can now use expressions in MDX to include JavaScript.
You can also use them as an escape hatch if you ever *just* want strings or JSX
rather than markdown:

```html language="mdx" chrome=no
{
  <h1>
    This just JSX, these *asterisks* have no meaning.
  </h1>
}

This is just {'`text`'}, not code.
```

More on expressions in MDX is in
[¶ Expressions in § What is MDX?][what-expressions]

### ESM

You can more easily embed components in MDX because blank lines are allowed:

```js chrome=no
export const Button = (props) => {
  const style = {color: 'red'}

  return <button style={style} {...props} />
}
```

We also fixed several cases where `import` and `export` were not parsed or
handled correctly or even crashed.
More on ESM in MDX is in [¶ ESM in § What is MDX?][what-esm]

### Markdown

We turned off several things that are allowed in regular markdown to make MDX
less ambiguous.
More on markdown in MDX and where it differs is in
[¶ Markdown in § What is MDX?][what-markdown]

### GFM

We turned off GFM features in MDX by default.
GFM extends CommonMark to add autolink literals, footnotes, strikethrough,
tables, and task lists.
If you do want these features, you can use a plugin.
How to do so is described in [our guide on GFM][guide-gfm].

## Update MDX content

The interface of the generated JavaScript from MDX changed:

*   Missing components now throw an error rather than render their children
    and emit a warning to the console, which is closer to how frameworks like
    React handle missing undefined JSX components
*   `parent.child` combos such as `ol.li`, to pass components, were removed, we
    recommend to style your `ol`s, `ul`s, and `li`s separately
*   The special component name `inlineCode` was removed, we recommend to use
    `pre` for the block version of code, and `code` for both the block and
    inline versions
*   `MDXContent.isMDXContent` was removed, we recommend treating `MDXContent`
    like any other component
*   Locally defined or imported components precede over passed components
*   We now “sandbox” components, for lack of a better name.
    It means that when you pass a component for `h1`, it does get used for
    `# hi` but not for `<h1>hi</h1>`
*   You can now pass and use objects of components: if you pass
    `components={{theme}}`, where `theme` is an object with a `Box` component,
    it can be used with: `<theme.Box>stuff</theme.Box>`
*   the values exports from an MDX file are no longer passed to layouts, you
    can achieve the same with:
    ```js
    import * as everything from './example.mdx'
    const {default: Content, ...exported} = everything
    <Content {...exported} />
    ```

We also fixed several cases where defined, imported, or passed components
weren’t handled correctly or even crashed.

***

Phew.
You made it!
Welcome on the MDX 2 train, it’s been a journey.
We know it wasn’t the easiest to migrate, we’re happy you’re still here, we’ll
try to make migration easier next time.
With our new AST, we’re able to create codemods from now on.
\<3

[support]: /community/support/

[contribute]: /community/contribute/

[esm]: #esm

[trouble]: /docs/troubleshooting-mdx/

[trouble-esm]: /docs/troubleshooting-mdx/#esm

[mdx-api]: /packages/mdx/#api

[remark-mdx-use]: /packages/remark-mdx/#use

[mdx-compile]: /packages/mdx/#compile

[mdx-compilesync]: /packages/mdx/#compilesync

[mdx-createprocessor]: /packages/mdx/#createprocessor

[mdx-evaluate]: /packages/mdx/#evaluate

[mdx-evaluatesync]: /packages/mdx/#evaluatesync

[mdx-react]: /packages/react/

[guide-gfm]: /guides/gfm/

[mdx-provider]: /docs/using-mdx/#mdx-provider

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

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

[mdx-file]: /packages/mdx/#file

[mdx-options-recmaplugins]: /packages/mdx/#optionsrecmaplugins

[mdx-options-remarkplugins]: /packages/mdx/#optionsremarkplugins

[mdx-options-rehypeplugins]: /packages/mdx/#optionsrehypeplugins

[mdx-options-jsximportsource]: /packages/mdx/#optionsjsximportsource

[mdx-options-providerimportsource]: /packages/mdx/#optionsproviderimportsource

[babel-loader]: https://webpack.js.org/loaders/babel-loader/

[loader-api]: /packages/loader/#api

[what-markdown]: /docs/what-is-mdx/#markdown

[what-jsx]: /docs/what-is-mdx/#jsx

[what-expressions]: /docs/what-is-mdx/#expressions

[what-esm]: /docs/what-is-mdx/#esm
