Reset not-found and error boundary when navigating (#49855)

## What?

Currently the error boundary state does not reset when a navigation
happens because the `key` does not change. Because of that navigating
using next/link when the error boundary is in the open state ends up not
rendering the contents of the new navigation, instead it keeps the error
boundary contents.

## How?

This PR uses a pattern that is recommended in the React docs (setState
during render) to reset the error boundary if the `usePathname` value
has changed, it is used as a proxy for a new navigation.

Fixes #47862
Fixes NEXT-963
Fixes #49736
Fixes #49732
Fixes #49599


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packages/next/src/client/components/error-boundary.tsx

@@ -1,6 +1,7 @@
 'use client'
 
 import React from 'react'
+import { usePathname } from './navigation'
 
 const styles = {
   error: {
@@ -36,19 +37,50 @@ export interface ErrorBoundaryProps {
   errorStyles?: React.ReactNode | undefined
 }
 
+interface ErrorBoundaryHandlerProps extends ErrorBoundaryProps {
+  pathname: string
+}
+
+interface ErrorBoundaryHandlerState {
+  error: Error | null
+  previousPathname: string
+}
+
 export class ErrorBoundaryHandler extends React.Component<
-  ErrorBoundaryProps,
-  { error: Error | null }
+  ErrorBoundaryHandlerProps,
+  ErrorBoundaryHandlerState
 > {
-  constructor(props: ErrorBoundaryProps) {
+  constructor(props: ErrorBoundaryHandlerProps) {
     super(props)
-    this.state = { error: null }
+    this.state = { error: null, previousPathname: this.props.pathname }
   }
 
   static getDerivedStateFromError(error: Error) {
     return { error }
   }
 
+  static getDerivedStateFromProps(
+    props: ErrorBoundaryHandlerProps,
+    state: ErrorBoundaryHandlerState
+  ): ErrorBoundaryHandlerState | null {
+    /**
+     * Handles reset of the error boundary when a navigation happens.
+     * Ensures the error boundary does not stay enabled when navigating to a new page.
+     * Approach of setState in render is safe as it checks the previous pathname and then overrides
+     * it as outlined in https://react.dev/reference/react/useState#storing-information-from-previous-renders
+     */
+    if (props.pathname !== state.previousPathname && state.error) {
+      return {
+        error: null,
+        previousPathname: props.pathname,
+      }
+    }
+    return {
+      error: state.error,
+      previousPathname: props.pathname,
+    }
+  }
+
   reset = () => {
     this.setState({ error: null })
   }
@@ -105,9 +137,11 @@ export function ErrorBoundary({
   errorStyles,
   children,
 }: ErrorBoundaryProps & { children: React.ReactNode }): JSX.Element {
+  const pathname = usePathname()
   if (errorComponent) {
     return (
       <ErrorBoundaryHandler
+        pathname={pathname}
         errorComponent={errorComponent}
         errorStyles={errorStyles}
       >

packages/next/src/client/components/not-found-boundary.tsx

@@ -1,4 +1,5 @@
 import React from 'react'
+import { usePathname } from './navigation'
 
 interface NotFoundBoundaryProps {
   notFound?: React.ReactNode
@@ -7,13 +8,25 @@ interface NotFoundBoundaryProps {
   children: React.ReactNode
 }
 
+interface NotFoundErrorBoundaryProps extends NotFoundBoundaryProps {
+  pathname: string
+}
+
+interface NotFoundErrorBoundaryState {
+  notFoundTriggered: boolean
+  previousPathname: string
+}
+
 class NotFoundErrorBoundary extends React.Component<
-  NotFoundBoundaryProps,
-  { notFoundTriggered: boolean }
+  NotFoundErrorBoundaryProps,
+  NotFoundErrorBoundaryState
 > {
-  constructor(props: NotFoundBoundaryProps) {
+  constructor(props: NotFoundErrorBoundaryProps) {
     super(props)
-    this.state = { notFoundTriggered: !!props.asNotFound }
+    this.state = {
+      notFoundTriggered: !!props.asNotFound,
+      previousPathname: props.pathname,
+    }
   }
 
   static getDerivedStateFromError(error: any) {
@@ -24,6 +37,28 @@ class NotFoundErrorBoundary extends React.Component<
     throw error
   }
 
+  static getDerivedStateFromProps(
+    props: NotFoundErrorBoundaryProps,
+    state: NotFoundErrorBoundaryState
+  ): NotFoundErrorBoundaryState | null {
+    /**
+     * Handles reset of the error boundary when a navigation happens.
+     * Ensures the error boundary does not stay enabled when navigating to a new page.
+     * Approach of setState in render is safe as it checks the previous pathname and then overrides
+     * it as outlined in https://react.dev/reference/react/useState#storing-information-from-previous-renders
+     */
+    if (props.pathname !== state.previousPathname && state.notFoundTriggered) {
+      return {
+        notFoundTriggered: false,
+        previousPathname: props.pathname,
+      }
+    }
+    return {
+      notFoundTriggered: state.notFoundTriggered,
+      previousPathname: props.pathname,
+    }
+  }
+
   render() {
     if (this.state.notFoundTriggered) {
       return (
@@ -45,8 +80,10 @@ export function NotFoundBoundary({
   asNotFound,
   children,
 }: NotFoundBoundaryProps) {
+  const pathname = usePathname()
   return notFound ? (
     <NotFoundErrorBoundary
+      pathname={pathname}
       notFound={notFound}
       notFoundStyles={notFoundStyles}
       asNotFound={asNotFound}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/error.tsx

@@ -0,0 +1,13 @@
+'use client'
+import Link from 'next/link'
+
+export default function ErrorComponent() {
+  return (
+    <>
+      <h1 id="error-component">Error Happened!</h1>
+      <Link href="/result" id="to-result">
+        To Result
+      </Link>
+    </>
+  )
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/layout.tsx

@@ -0,0 +1,7 @@
+export default function Root({ children }: { children: React.ReactNode }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  )
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/not-found.tsx

@@ -0,0 +1,12 @@
+import Link from 'next/link'
+
+export default function NotFound() {
+  return (
+    <>
+      <h1 id="not-found-component">Not Found!</h1>
+      <Link href="/result" id="to-result">
+        To Result
+      </Link>
+    </>
+  )
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/page.tsx

@@ -0,0 +1,3 @@
+export default function Page() {
+  return <h1 id="homepage">Home</h1>
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/result/page.tsx

@@ -0,0 +1,3 @@
+export default function Page() {
+  return <h1 id="result-page">Result Page!</h1>
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/trigger-404/page.tsx

@@ -0,0 +1,7 @@
+import { notFound } from 'next/navigation'
+
+export const dynamic = 'force-dynamic'
+
+export default function Page() {
+  notFound()
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/app/trigger-error/page.tsx

@@ -0,0 +1,5 @@
+export const dynamic = 'force-dynamic'
+
+export default function Page() {
+  throw new Error('This is an error')
+}

test/e2e/app-dir/error-boundary-and-not-found-linking/error-boundary-and-not-found-linking.test.ts

@@ -0,0 +1,39 @@
+import { createNextDescribe } from 'e2e-utils'
+
+createNextDescribe(
+  'not-found-linking',
+  {
+    files: __dirname,
+  },
+  ({ next }) => {
+    it('should allow navigation on not-found', async () => {
+      const browser = await next.browser('/trigger-404')
+      expect(await browser.elementByCss('#not-found-component').text()).toBe(
+        'Not Found!'
+      )
+
+      expect(
+        await browser
+          .elementByCss('#to-result')
+          .click()
+          .waitForElementByCss('#result-page')
+          .text()
+      ).toBe('Result Page!')
+    })
+
+    it('should allow navigation on error', async () => {
+      const browser = await next.browser('/trigger-error')
+      expect(await browser.elementByCss('#error-component').text()).toBe(
+        'Error Happened!'
+      )
+
+      expect(
+        await browser
+          .elementByCss('#to-result')
+          .click()
+          .waitForElementByCss('#result-page')
+          .text()
+      ).toBe('Result Page!')
+    })
+  }
+)

test/e2e/app-dir/error-boundary-and-not-found-linking/next.config.js

@@ -0,0 +1,10 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {
+  typescript: {
+    ignoreBuildErrors: true,
+  },
+}
+
+module.exports = nextConfig

test/e2e/app-dir/navigation/app/not-found/not-found.js

@@ -1,9 +1,15 @@
+import Link from 'next/link'
 import styles from './style.module.css'
 
 export default function NotFound() {
   return (
-    <h1 id="not-found-component" className={styles.red}>
-      Not Found!
-    </h1>
+    <>
+      <h1 id="not-found-component" className={styles.red}>
+        Not Found!
+      </h1>
+      <Link href="/not-found/result" id="to-result">
+        To Result
+      </Link>
+    </>
   )
 }

test/e2e/app-dir/navigation/app/not-found/result/page.js

@@ -0,0 +1,3 @@
+export default function Page() {
+  return <h1 id="result-page">Result Page!</h1>
+}

test/e2e/app-dir/navigation/app/not-found/servercomponent/page.js

@@ -1,4 +1,3 @@
-// TODO-APP: enable when flight error serialization is implemented
 import { notFound } from 'next/navigation'
 
 export default function Page() {

test/e2e/app-dir/navigation/app/not-found/with-link/page.js

@@ -0,0 +1,8 @@
+import { notFound } from 'next/navigation'
+
+export const dynamic = 'force-dynamic'
+
+export default function Page() {
+  notFound()
+  return <></>
+}