Commit graph

84 commits

Author SHA1 Message Date
Balázs Orbán
6178e7cf6d
fix: make sure image-config gets transpiled (#34677) 2022-02-22 09:27:18 -05:00
Shu Ding
b701de60cd
Improve type imports in server/render and optimize the Edge SSR loader (#34552)
* reorganize imports

* code refactoring

* remove unused variables

* fix test

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
2022-02-19 22:13:48 +01:00
Gerald Monaco
204a95586d
Remove useMaybeDeferContent hook (#34506) 2022-02-18 13:07:19 -06:00
Jiachi Liu
ce76d1712e
Leverage existing component checking warning for streaming (#34526)
## Bug

Fixes: #31993

* Remove the simple component checking in middleware ssr
* Leverage existing components checking for Component / App / Document, if any of these component is not valid react type or is undefined nextjs will error in dev mode with redbox. Like above.

<img width="826" alt="image" src="https://user-images.githubusercontent.com/4800338/154668945-bcee24ee-17aa-4afd-acda-9f8b249891ac.png">


- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
2022-02-18 15:25:10 +00:00
Gerald Monaco
944c734d04
Add unstable_useFlushEffects hook (#34117)
Implements https://github.com/vercel/next.js/issues/30997 with some minor tweaks to the design:

* The hook is moved to Client Components (e.g. `pages/_app` instead of `pages/_document`). This was a silly oversight in the original design: the hook needs to be called during server prerendering.

* `useFlushEffects` instead of `useFlushEffect` as there isn't a particularly safe way to implement the singular semantics as a Client Component hook given the current implementation of server rendering.

---

Fixes #30997
2022-02-18 00:18:28 +00:00
Balázs Orbán
eddabd98f8
refactor: move HtmlContext (#34482)
The shared utils file included an import from `react` (because it was using `createContext`) which seems to be unnecessary in the Middleware bundle.

With this PR and steps #34425 laid out, the bundle size did decrease without breaking functionality.

![image](https://user-images.githubusercontent.com/18369201/154508389-0a813e3e-1e07-4c45-8b71-444cc54a7f9e.png)

Fixes #34425

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2022-02-17 18:21:40 +00:00
Shu Ding
d4d79b2d9b
Fix chunk buffering for server components (#34474) 2022-02-17 09:05:15 -06:00
Balázs Orbán
9639fe704c
Ensure we don't poll page in development when notFound: true is returned (#34352)
Fixes: #34342

Visiting the following page will call gSSP indefinitely in a loop and logs errors from `on-demand-entries-client`:
```js
const Home = () => null
export default Home
        
export function getServerSideProps() {
  console.log("gssp called")
  return { notFound: true }
}
```

We should not keep fetching the page if it returns 404 as  it can introduce unnecessary data requests.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`



Co-authored-by: JJ Kasper <22380829+ijjk@users.noreply.github.com>
2022-02-16 18:53:48 +00:00
Alex Castle
f516304649
Remove experimental image optimization feature (#34349)
This PR removes the experimental `optimizeImages` flag. This feature was designed to automatically add preload tags for images, but I was never able to get it to do a very good job of selecting the images that actually need preloading.

This feature never graduated from experimental and in fact we never even publicized it as an experimental feature for people to try.

Additionally, even if someone was using this feature, it wouldn't have a functional effect, only a performance effect (removal of some preloads).

For those reasons, I believe it is safe to remove this functionality and that it is not a breaking change.
2022-02-15 01:36:51 +00:00
Shu Ding
6bc7c4d9c2
Optimize the web server size (#34242)
Related to #34185, this PR reduces the size of chunk that contains web-server.ts from 1.14mb to 210.8kb, by splitting base-http and api-utils into different environments.

Only affected thing is we can't have SSG preview mode for the web runtime via `getStaticProps`.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2022-02-11 19:56:25 +00:00
Shu Ding
931666dd3c
Fix uncaught error in getInitialProps when runtime is set to nodejs (#34228)
This PR ensures that the test "should render 500 error correctly" doesn't break when `runtime` is set to `nodejs` with `serverComponents` enabled.

This test case is now moved to the "basic" suite to ensure it doesn't break in both runtimes. And "should not bundle external imports into client builds for RSC" is enabled for the `nodejs` runtime too.

## Bug

- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2022-02-11 18:30:39 +00:00
Jiachi Liu
4f8ffed4bf
Fix reuse of inline flight response and 404 for RSC in node runtime (#34202)
### Fixes

* We need give value for `__flight__` query or it will lost in node runtime
* Match the cache key of flight response (`path + search`, `route, `id`)
* Flight response should return `200` instead of `404` for 404 page

### Tests

* Run rsc for node runtime test suite
* Add more cases for 404
2022-02-10 21:13:52 +00:00
Gerald Monaco
3e6035937a
Fix: Use react-dom/server.browser when reactRoot: true (#34116)
Since we want to use the streaming renderer when `reactRoot: true`, we have to make sure we use the right server implementation too.
2022-02-09 03:48:52 +00:00
JuniorTour
e2d6c311b5
fix: next/image usage from node_modules (#33559)
fix: image config not work for `node_modules`

Co-authored-by: Steven <steven@ceriously.com>
2022-02-08 19:55:53 -05:00
Shu Ding
eb3cba388c
Polyfill pipeTo and pipeThrough (#34112)
* polyfill pipeTo

* add pipeThrough

* covert pipeThrough calls

* use pipe

* invert logic

Co-authored-by: Jiachi Liu <inbox@huozhi.im>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
2022-02-08 22:40:25 +01:00
Gerald Monaco
df29561ae3
Use renderToStream with React 18 (#34106)
As per React 18 recommendation, we should use e.g. `renderToReadableStream` whenever we use `createRoot`. This is particularly important for currently supported suspense features like `React.lazy` to work properly during SSR.

However, unless you have opted in to streaming support (via [the `runtime` flag](https://github.com/vercel/next.js/pull/34068)), we will wait until `onCompleteAll` before sending it (via the `generateStaticHTML` flag).

---

Fixes #33879
2022-02-08 19:39:27 +00:00
Shu Ding
6944074506
Deprecate concurrentFeatures with runtime (#34068) 2022-02-08 14:16:46 +01:00
Gerald Monaco
1aeb230839
Fix suffix ordering while streaming (#34011)
* Fix suffix ordering

* Don't start reading until after resolving

* More yak shaving
2022-02-05 13:17:29 -06:00
Gerald Monaco
7e0b8aa4d1
Use ReadableStream in RenderResult (#34005)
Since we're always using `ReadableStream`, we should just get rid of `ResultPiper`.

This also lets us replace things like `bufferedReadFromReadableStream` with a `TransformStream` that does the same thing, so that it's `TransformStream`s all the way down.

Finally, we can get rid of the one-off call to `renderToReadableStream` and just use `renderToStream` whenever we're rendering a concurrent tree.
2022-02-05 01:13:02 +00:00
Gerald Monaco
0b1d5e17bc
Use react-dom/server.browser in Node.js (#33950)
Instead of branching rendering based on Node.js and browser/web runtimes, we should just use the web version for now, which can run as-is on versions >=16.5.0 of Node.js, polyfilling `ReadableStream` on older versions when necessary.

There are a few potential downsides to this, as React is less able to optimize flushing and execution. We can revisit that in the future though if desired.
2022-02-04 17:52:53 +00:00
Jiachi Liu
41614e52d7
Fix broken html on streaming render for error page (#33399)
## Bug

Fixes: #32515

Previously, we render the `suffix` after consuming 1st chunk, instead we should render it after stream finished

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
2022-01-17 20:27:12 +00:00
Oleg Zuev
8dc46705f2
Replace regexp to plain string for optimization render HTML (#33306)
## Bug

Line `const [renderTargetPrefix, renderTargetSuffix] = documentHTML.split(*)` with RegExp almost 80 times slower than a plain string.

Before:
![telegram-cloud-photo-size-2-5409140542421448593-y](https://user-images.githubusercontent.com/22259080/149506024-84365840-5b0f-481f-b05f-1381d839c579.jpg)


After:
![telegram-cloud-photo-size-2-5409140542421448594-y](https://user-images.githubusercontent.com/22259080/149506036-0df69ae7-e265-40da-a865-73c84496aa58.jpg)
2022-01-17 16:22:44 +00:00
JJ Kasper
25d064f812
Pre-compile more dependencies (#32742)
This ncc's some remaining dependencies bringing us under 20 install time dependencies (including nested dependencies), this also reduces install size by another `2.75 MB`. A follow-up PR will investigate a custom install script for our swc packages to allow us to remove the `optionalDependencies` which is slowing down install time as well. 

x-ref: https://github.com/vercel/next.js/pull/32679
x-ref: https://github.com/vercel/next.js/pull/32627
x-ref: https://github.com/vercel/next.js/issues/31887
x-ref: https://github.com/vercel/styled-jsx/pull/770
2022-01-17 15:17:22 +00:00
JJ Kasper
02405e2247
Fix getServerSideProps hanging in dev on early end (#33366)
This fixes the case where calling `res.end()` is `getServerSideProps` would cause the request to hang in development due to our `Proxy` around `res` causing internal `ServerResponse` fields to not be available ([related post](https://javascript.info/proxy#built-in-objects-internal-slots)). I also migrated our `getServerSideProps` test suite to an e2e suite with a test for this case. 

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`

Fixes: https://github.com/vercel/next.js/issues/15118
Fixes: https://github.com/vercel/next.js/issues/32824
Closes: https://github.com/vercel/next.js/pull/33129
2022-01-16 16:14:21 +00:00
Jiachi Liu
00a843280d
Custom app for server components (#33149)
## Feature

Resolves #30996

- [x] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
2022-01-14 13:01:00 +00:00
Jiachi Liu
6581ba9dae
Bust cache for RSC in each render (#32710)
* flight response should not be cached since it's could be changed per fetching
* delete cache after readRoot has constructed react tree
2021-12-21 23:37:23 +00:00
Jiachi Liu
c5291406aa
Escape from next head in rsc _error page (#32624)
* Don't render `next/head` in _error for RSC
* Save an error in `__next_s` for client to be aware RSC rendering is errored
* Fix `req.url` when errored
* Refactor some changes in middleware ssr loader
2021-12-21 19:24:57 +00:00
Shu Ding
8b12b174e5
Fix writing strings to the writable stream writer (#32637)
Only chunks are allowed to write to writable. This fixes the following error in the web runtime:

```
Uncaught (in promise) TypeError: This TransformStream is being used as a byte stream, but received a string on its
writable side. If you wish to write a string, you'll probably want to explicitly UTF-8-encode it with TextEncoder.
```

It doesn't fail in the Node.js sandbox since we polyfilled this case (which should be reverted back later).

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-12-18 18:39:36 +00:00
Jiachi Liu
b58a3f0b9d
Add options to defaultGetInitialProps and upgrade styled-jsx-with-csp example (#32594)
x-ref: https://github.com/vercel/styled-jsx/issues/763

* Add 2nd arg `options` to `docCtx.defaultGetInitialProps` to make customization easier
* Upgrade styled-jsx to fit typing
* Update styled-jsx csp example
2021-12-17 23:27:56 +00:00
Shu Ding
346670ca6c
Fix ReadableStream.pipeTo() being unimplemented in the web runtime (#32602)
Currently we are using a TransformStream to process the forwarded stream for the inlined data, but unfortunately the `pipeTo` method is not implemented in the web runtime. This PR changes it to a naive way of doing so.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-12-17 12:27:53 +00:00
Shu Ding
8f9aed687a
Fixes for inline embedding data in the web runtime (#32471)
* fix missing renderToString

* workaround tee

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
2021-12-14 00:48:36 +01:00
Oriol Collell
eba9da09eb
Fixes #32338 missing Document components trigger an error for production builds (#32345)
* Only validate _document subcomponents in dev environment

* Replace error by a warning

Co-authored-by: JJ Kasper <jj@jjsweb.site>
2021-12-13 16:47:34 -06:00
Shu Ding
438ee9618f
Inline server data response with partial hydration (#32330)
This PR implements the basic inline embedded server response data (#30994) for RSC, as well as partial hydration (#31338) for RSC and React 18 SSR streaming.

For #30994, `renderTargetSuffix` is passed to the `bodyResult` resolver so the stream can inject corresponding hydration scripts and the closing body tag at the correct time. The expected behavior should be _prefix_, _body shell_, _suffix scripts_, _stream and inlined data_, _close body_.

For #31338, we have to force turn on `disableOptimizedLoading` when `concurrentFeatures` is enabled to opt-out of deferred script tags.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [x] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-12-13 10:48:18 +00:00
Jiachi Liu
6f8cf675d3
Add unstable_useRefreshRoot (#32342)
## Feature

Resolves #32332

- [x] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
2021-12-10 10:22:31 +00:00
Gerald Monaco
aa32deb467
Simplify custom Writable (#32247)
* Simplify custom writable

* Fix draining
2021-12-08 12:03:07 -06:00
Gerald Monaco
9bcf678e64
Revert support for render prop in <Main /> (#32184)
Reverts support for render prop in `<Main />` in `Document`. This was added just to support the `useFlushEffect` hook, but we've tweaked the design a bit, moving it to `App`.
2021-12-06 21:22:05 +00:00
Jiachi Liu
928c77958e
Resolve streaming data for flight requests (#32010)
## Bug

- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
2021-12-01 15:48:31 +00:00
Gerald Monaco
2b5d62dcad
Stop using environment variables in pages/_document (#31946)
Since #31939 is going to move the `Document` components, we can't rely on `DefinePlugin` to provide environment variables. This PR passes them as render opts instead. We can't just force this to be bundled like e.g. `next/dynamic`, because we use it internally.
2021-11-30 17:14:28 +00:00
Shu Ding
d577edd206
Fix auto export condition in edge SSR (#31845)
`isAutoExport` should be `false` when `concurrentFeatures` is enabled.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-11-26 15:53:38 +00:00
Jiachi Liu
7f58a2e49f
Add cookies and headers for request using in RSC (#31623)
* Passdown the request with richer information
* test: access request header as prop from gSSP
2021-11-22 18:53:22 +00:00
JJ Kasper
e8ca334d42
Fix non-concurrent function _document (#31628)
This ensures functional `_document` is rendered correctly when not using concurrent mode. 

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

Fixes: https://github.com/vercel/next.js/issues/31593
x-ref: https://github.com/vercel/next.js/pull/30156
2021-11-19 19:41:19 +00:00
Gerald Monaco
ab712ef310
Move root div to an app wrapper (#31596)
Extracted from #31223.

We need to move the root `<div id="__next">` wrapper to be rendered as part of the page content, rather than the`Document`, so that flush effects (like styles) are flushed before (or after) the div, rather than inside, where they would cause hydration mismatches.
2021-11-19 08:16:05 +00:00
Gerald Monaco
9f7c774665
Minor simplifications to renderToWebStream (#31553)
Simplifies `renderToWebStream` a little bit for #31223
2021-11-18 19:46:15 +00:00
Gerald Monaco
0cf7061859
Make missing Document components an error (#31505)
* Make missing document components an error

* Fix broken tests
2021-11-17 13:34:16 -06:00
Jiachi Liu
055e28ef81
Ensure only one doctype is rendered (#31534)
React-dom renders doctype automatically when `<html>` is detected. We should append `DOCTYPE` prefix only when necessary.
x-ref: https://github.com/facebook/react/pull/21680

## Bug

![image](https://user-images.githubusercontent.com/4800338/142215292-4af4a61d-2d75-48ae-a31a-0af641c72dcf.png)

- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
2021-11-17 14:57:48 +00:00
Shu Ding
16d56e2c49
Refactor server/render for SSR streaming (#31231)
Initial step to refactor the rendering logic by decoupling the handler and renderer:
1. Delegate Flight rendering to server/render
2. Reuse the piper glue code for both Fizz and Flight streams
3. Add buffering for ReadableStream

In 1), this PR also makes sure that gSSP/gSP are correctly executed before the Flight stream and `pageProps` and `router` are correctly delivered to the component.

Related to #30994.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-11-15 15:29:34 +00:00
Jiachi Liu
cf206a8392
Resolve stream piper on complete shell for renderToReadableStream (#31186)
1. Align `renderToReadableStream` with `renderToNodeStream`, resolve promise of `NodeWritablePiper` only when `onCompleteShell` is called.
2. update webpack to disable chunk loading for web runtime

Item 1 is the preparation for middleware-ssr-loader. Then we can do the following there

```js
try {
   result = await renderToHTML(page)
} catch (e) {
   result = await renderToHTML(errorPage)
}
result.pipe(renderResult)
```
2021-11-12 00:00:54 +00:00
Javi Velasco
5fc4325aa6
Fix middleware i18n rewrites (#31174)
Fixes #30897

This PR fixes the linked issue where rewrites are not being applied for locale. It adds the corresponding test but also, as it was added in debugging process, it introduces a helper to read/write into the `request` object.

We are currently writing directly into the request by casting to `any` and then using flags like `_nextRewrote`. Instead, this PR puts all of this metadata under a symbol so it is not directly accessible. This also allows to have a single place where all of this metadata is listed so we can add comments describing the purpose of each flag.

In the same way, there is metadata written in the querystring. This is adding some types for it in order to throw some visibility on where is this metadata accessed. In an upcoming PR we can move all of it to the `request` object if possible to simplify the system.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
2021-11-09 01:28:39 +00:00
Shu Ding
960298b344
Fix useId mismatches on hydration (#31102)
Fixes #30876.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
2021-11-08 23:32:06 +00:00
Gerald Monaco
ad981783ab
Add render prop support to <Main> (#30156)
Adds support for render props to the `<Main>` component, when using the [functional custom `Document`](https://github.com/vercel/next.js/pull/28515) style. This allows you to write something like this:

```tsx
export default function Document() {
  const jsxStyleRegistry = createStyleRegistry()
  return (
    <Html>
      <Head />
      <body>
        <Main>
          {content => (
            <StyledJsxWrapper registry={jsxStyleRegistry}>
              {content}
            </StyledJsxWrapper>
          )}
        </Main>
        <NextScript />
      </body>
    </Html>
  )
}
```

In functional document components, this allows the `<App>` to be wrapped, similar to `enhanceApp` (which is only available via `getInitialProps`, which is not supported by functional document components). The primary use for this is for integrating with 3rd party CSS-in-JS libraries, allowing them to attach an `useFlush` handler to [support React 18](https://github.com/reactwg/react-18/discussions/110):

```tsx
import { unstable_useFlush as useFlush } from 'next/document'

export default function StyledJsxWrapper({ children, registry }) {
  useFlush(() => {
    /* ... */
  })
  return (
    <StyleRegistry registry={registry}>
      {children}
    </StyleRegistry>
  )
}
```

Support for `useFlush` will be added in a follow up PR.
2021-11-07 17:36:39 +00:00