How to upgrade to version 9

Source URL: https://nextjs.org/docs/pages/guides/upgrading/version-9

How to upgrade to version 9

To upgrade to version 9, run the following command:

npm i next@9

yarn add next@9

pnpm up next@9

bun add next@9

Good to know: If you are using TypeScript, ensure you also upgrade @types/react and @types/react-dom to their corresponding versions.

Check your Custom App File (pages/_app.js)

If you previously copied the Custom <App> example, you may be able to remove your getInitialProps.

Removing getInitialProps from pages/_app.js (when possible) is important to leverage new Next.js features!

The following getInitialProps does nothing and may be removed:

class MyApp extends App {
  // Remove me, I do nothing!
  static async getInitialProps({ Component, ctx }) {
    let pageProps = {}

    if (Component.getInitialProps) {
      pageProps = await Component.getInitialProps(ctx)
    }

    return { pageProps }
  }

  render() {
    // ... etc
  }
}

Breaking Changes

@zeit/next-typescript is no longer necessary

Next.js will now ignore usage @zeit/next-typescript and warn you to remove it. Please remove this plugin from your next.config.js.

Remove references to @zeit/next-typescript/babel from your custom .babelrc (if present).

The usage of fork-ts-checker-webpack-plugin should also be removed from your next.config.js.

TypeScript Definitions are published with the next package, so you need to uninstall @types/next as they would conflict.

The following types are different:

This list was created by the community to help you upgrade, if you find other differences please send a pull-request to this list to help other users.

From:

import { NextContext } from 'next'
import { NextAppContext, DefaultAppIProps } from 'next/app'
import { NextDocumentContext, DefaultDocumentIProps } from 'next/document'

to

import { NextPageContext } from 'next'
import { AppContext, AppInitialProps } from 'next/app'
import { DocumentContext, DocumentInitialProps } from 'next/document'

The config key is now an export on a page

You may no longer export a custom variable named config from a page (i.e. export { config } / export const config ...). This exported variable is now used to specify page-level Next.js configuration like Opt-in AMP and API Route features.

You must rename a non-Next.js-purposed config export to something different.

next/dynamic no longer renders “loading…” by default while loading

Dynamic components will not render anything by default while loading. You can still customize this behavior by setting the loading property:

import dynamic from 'next/dynamic'

const DynamicComponentWithCustomLoading = dynamic(
  () => import('../components/hello2'),
  {
    loading: () => <p>Loading</p>,
  }
)

withAmp has been removed in favor of an exported configuration object

Next.js now has the concept of page-level configuration, so the withAmp higher-order component has been removed for consistency.

This change can be automatically migrated by running the following commands in the root of your Next.js project:

curl -L https://github.com/vercel/next-codemod/archive/master.tar.gz | tar -xz --strip=2 next-codemod-master/transforms/withamp-to-config.js npx jscodeshift -t ./withamp-to-config.js pages/**/*.js

To perform this migration by hand, or view what the codemod will produce, see below:

Before

import { withAmp } from 'next/amp'

function Home() {
  return <h1>My AMP Page</h1>
}

export default withAmp(Home)
// or
export default withAmp(Home, { hybrid: true })

After

export default function Home() {
  return <h1>My AMP Page</h1>
}

export const config = {
  amp: true,
  // or
  amp: 'hybrid',
}

next export no longer exports pages as index.html

Previously, exporting pages/about.js would result in out/about/index.html. This behavior has been changed to result in out/about.html.

You can revert to the previous behavior by creating a next.config.js with the following content:

module.exports = {
  trailingSlash: true,
}

pages/api/ is treated differently

Pages in pages/api/ are now considered API Routes. Pages in this directory will no longer contain a client-side bundle.

Deprecated Features

next/dynamic has deprecated loading multiple modules at once

The ability to load multiple modules at once has been deprecated in next/dynamic to be closer to React’s implementation (React.lazy and Suspense).

Updating code that relies on this behavior is relatively straightforward! We’ve provided an example of a before/after to help you migrate your application:

Before

import dynamic from 'next/dynamic'

const HelloBundle = dynamic({
  modules: () => {
    const components = {
      Hello1: () => import('../components/hello1').then((m) => m.default),
      Hello2: () => import('../components/hello2').then((m) => m.default),
    }

    return components
  },
  render: (props, { Hello1, Hello2 }) => (
    <div>
      <h1>{props.title}</h1>
      <Hello1 />
      <Hello2 />
    </div>
  ),
})

function DynamicBundle() {
  return <HelloBundle title="Dynamic Bundle" />
}

export default DynamicBundle

After

import dynamic from 'next/dynamic'

const Hello1 = dynamic(() => import('../components/hello1'))
const Hello2 = dynamic(() => import('../components/hello2'))

function HelloBundle({ title }) {
  return (
    <div>
      <h1>{title}</h1>
      <Hello1 />
      <Hello2 />
    </div>
  )
}

function DynamicBundle() {
  return <HelloBundle title="Dynamic Bundle" />
}

export default DynamicBundle

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