feat(app): add experimental.missingSuspenseWithCSRBailout (vercel#57642)

### What?

This PR adds a new flag called
`experimental.missingSuspenseWithCSRBailout`.

### Why?

Via this PR we can break a build when calling `useSearchParams` without
wrapping it in a suspense boundary.

If no suspense boundaries are present, Next.js must avoid doing SSR and
defer the entire page's rendering to the client. This is not a great
default. Instead, we will now break the build so that you are forced to
add a boundary.

### How?

Add an experimental flag. If a `BailoutToCSRError` error is thrown and
this flag is enabled, the build should fail and log an error, instead of
showing a warning and bail the entire page to client-side rendering.

Closes NEXT-1770

---------

Co-authored-by: Balázs Orbán <[email protected]>
Co-authored-by: Wyatt Johnson <[email protected]>

Author: 3 people

errors/missing-suspense-with-csr-bailout.mdx

@@ -0,0 +1,15 @@
+---
+title: Missing Suspense with CSR Bailout
+---
+
+#### Why This Error Occurred
+
+Certain methods like `useSearchParams()` opt Next.js into client-side rendering. Without a suspense boundary, this will opt the entire page into client-side rendering, which is likely not intended.
+
+#### Possible Ways to Fix It
+
+Make sure that the method is wrapped in a suspense boundary. This way Next.js will only opt the component into client-side rendering up to the suspense boundary.
+
+### Useful Links
+
+- [`useSearchParams`](https://nextjs.org/docs/app/api-reference/functions/use-search-params)

packages/next/src/client/components/bailout-to-client-rendering.ts

@@ -1,14 +1,11 @@
-import { throwWithNoSSR } from '../../shared/lib/lazy-dynamic/no-ssr-error'
+import { BailoutToCSRError } from '../../shared/lib/lazy-dynamic/bailout-to-csr'
 import { staticGenerationAsyncStorage } from './static-generation-async-storage.external'
 
-export function bailoutToClientRendering(): void | never {
+export function bailoutToClientRendering(reason: string): void | never {
   const staticGenerationStore = staticGenerationAsyncStorage.getStore()
 
-  if (staticGenerationStore?.forceStatic) {
-    return
-  }
+  if (staticGenerationStore?.forceStatic) return
 
-  if (staticGenerationStore?.isStaticGeneration) {
-    throwWithNoSSR()
-  }
+  if (staticGenerationStore?.isStaticGeneration)
+    throw new BailoutToCSRError(reason)
 }

packages/next/src/client/components/navigation.ts

@@ -92,7 +92,7 @@ export function useSearchParams(): ReadonlyURLSearchParams {
     const { bailoutToClientRendering } =
       require('./bailout-to-client-rendering') as typeof import('./bailout-to-client-rendering')
     // TODO-APP: handle dynamic = 'force-static' here and on the client
-    bailoutToClientRendering()
+    bailoutToClientRendering('useSearchParams()')
   }
 
   return readonlySearchParams

packages/next/src/client/on-recoverable-error.ts

@@ -1,6 +1,6 @@
-import { isBailoutCSRError } from '../shared/lib/lazy-dynamic/no-ssr-error'
+import { isBailoutToCSRError } from '../shared/lib/lazy-dynamic/bailout-to-csr'
 
-export default function onRecoverableError(err: any) {
+export default function onRecoverableError(err: unknown) {
   // Using default react onRecoverableError
   // x-ref: https://github.com/facebook/react/blob/d4bc16a7d69eb2ea38a88c8ac0b461d5f72cdcab/packages/react-dom/src/client/ReactDOMRoot.js#L83
   const defaultOnRecoverableError =
@@ -13,7 +13,7 @@ export default function onRecoverableError(err: any) {
         }
 
   // Skip certain custom errors which are not expected to be reported on client
-  if (isBailoutCSRError(err)) return
+  if (isBailoutToCSRError(err)) return
 
   defaultOnRecoverableError(err)
 }

packages/next/src/export/helpers/is-dynamic-usage-error.ts

@@ -1,10 +1,8 @@
 import { DYNAMIC_ERROR_CODE } from '../../client/components/hooks-server-context'
 import { isNotFoundError } from '../../client/components/not-found'
 import { isRedirectError } from '../../client/components/redirect'
-import { isBailoutCSRError } from '../../shared/lib/lazy-dynamic/no-ssr-error'
 
 export const isDynamicUsageError = (err: any) =>
   err.digest === DYNAMIC_ERROR_CODE ||
   isNotFoundError(err) ||
-  isBailoutCSRError(err) ||
   isRedirectError(err)

packages/next/src/export/index.ts

@@ -506,7 +506,11 @@ export async function exportAppImpl(
       : {}),
     strictNextHead: !!nextConfig.experimental.strictNextHead,
     deploymentId: nextConfig.experimental.deploymentId,
-    experimental: { ppr: nextConfig.experimental.ppr === true },
+    experimental: {
+      ppr: nextConfig.experimental.ppr === true,
+      missingSuspenseWithCSRBailout:
+        nextConfig.experimental.missingSuspenseWithCSRBailout,
+    },
   }
 
   const { serverRuntimeConfig, publicRuntimeConfig } = nextConfig

packages/next/src/export/routes/pages.ts

@@ -15,7 +15,7 @@ import {
   NEXT_DATA_SUFFIX,
   SERVER_PROPS_EXPORT_ERROR,
 } from '../../lib/constants'
-import { isBailoutCSRError } from '../../shared/lib/lazy-dynamic/no-ssr-error'
+import { isBailoutToCSRError } from '../../shared/lib/lazy-dynamic/bailout-to-csr'
 import AmpHtmlValidator from 'next/dist/compiled/amphtml-validator'
 import { FileType, fileExists } from '../../lib/file-exists'
 import { lazyRenderPagesPage } from '../../server/future/route-modules/pages/module.render'
@@ -105,10 +105,8 @@ export async function exportPages(
         query,
         renderOpts
       )
-    } catch (err: any) {
-      if (!isBailoutCSRError(err)) {
-        throw err
-      }
+    } catch (err) {
+      if (!isBailoutToCSRError(err)) throw err
     }
   }
 
@@ -163,10 +161,8 @@ export async function exportPages(
           { ...query, amp: '1' },
           renderOpts
         )
-      } catch (err: any) {
-        if (!isBailoutCSRError(err)) {
-          throw err
-        }
+      } catch (err) {
+        if (!isBailoutToCSRError(err)) throw err
       }
 
       const ampHtml =

packages/next/src/export/worker.ts

@@ -35,6 +35,7 @@ import { createIncrementalCache } from './helpers/create-incremental-cache'
 import { isPostpone } from '../server/lib/router-utils/is-postpone'
 import { isMissingPostponeDataError } from '../server/app-render/is-missing-postpone-error'
 import { isDynamicUsageError } from './helpers/is-dynamic-usage-error'
+import { isBailoutToCSRError } from '../shared/lib/lazy-dynamic/bailout-to-csr'
 
 const envConfig = require('../shared/lib/runtime-config.external')
 
@@ -318,9 +319,11 @@ async function exportPageImpl(
     // if this is a postpone error, it's logged elsewhere, so no need to log it again here
     if (!isMissingPostponeDataError(err)) {
       console.error(
-        `\nError occurred prerendering page "${path}". Read more: https://nextjs.org/docs/messages/prerender-error\n` +
-          (isError(err) && err.stack ? err.stack : err)
+        `\nError occurred prerendering page "${path}". Read more: https://nextjs.org/docs/messages/prerender-error\n`
       )
+      if (!isBailoutToCSRError(err)) {
+        console.error(isError(err) && err.stack ? err.stack : err)
+      }
     }
 
     return { error: true }

packages/next/src/server/app-render/app-render.tsx

@@ -63,7 +63,7 @@ import { parseAndValidateFlightRouterState } from './parse-and-validate-flight-r
 import { validateURL } from './validate-url'
 import { createFlightRouterStateFromLoaderTree } from './create-flight-router-state-from-loader-tree'
 import { handleAction } from './action-handler'
-import { isBailoutCSRError } from '../../shared/lib/lazy-dynamic/no-ssr-error'
+import { isBailoutToCSRError } from '../../shared/lib/lazy-dynamic/bailout-to-csr'
 import { warn, error } from '../../build/output/log'
 import { appendMutableCookies } from '../web/spec-extension/adapters/request-cookies'
 import { createServerInsertedHTML } from './server-inserted-html'
@@ -996,12 +996,19 @@ async function renderToHTMLOrFlightImpl(
           throw err
         }
 
-        // True if this error was a bailout to client side rendering error.
-        const shouldBailoutToCSR = isBailoutCSRError(err)
+        /** True if this error was a bailout to client side rendering error. */
+        const shouldBailoutToCSR = isBailoutToCSRError(err)
         if (shouldBailoutToCSR) {
+          console.log()
+
+          if (renderOpts.experimental.missingSuspenseWithCSRBailout) {
+            error(
+              `${err.message} should be wrapped in a suspense boundary at page "${pagePath}". https://nextjs.org/docs/messages/missing-suspense-with-csr-bailout`
+            )
+            throw err
+          }
           warn(
-            `Entire page ${pagePath} deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering`,
-            pagePath
+            `Entire page "${pagePath}" deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering`
           )
         }
 
@@ -1212,7 +1219,7 @@ async function renderToHTMLOrFlightImpl(
     renderOpts.experimental.ppr &&
     staticGenerationStore.postponeWasTriggered &&
     !metadata.postponed &&
-    (!response.err || !isBailoutCSRError(response.err))
+    (!response.err || !isBailoutToCSRError(response.err))
   ) {
     // a call to postpone was made but was caught and not detected by Next.js. We should fail the build immediately
     // as we won't be able to generate the static part

packages/next/src/server/app-render/create-error-handler.tsx

@@ -3,6 +3,7 @@ import { formatServerError } from '../../lib/format-server-error'
 import { SpanStatusCode, getTracer } from '../lib/trace/tracer'
 import { isAbortError } from '../pipe-readable'
 import { isDynamicUsageError } from '../../export/helpers/is-dynamic-usage-error'
+import { isBailoutToCSRError } from '../../shared/lib/lazy-dynamic/bailout-to-csr'
 
 export type ErrorHandler = (err: any) => string | undefined
 
@@ -34,11 +35,12 @@ export function createErrorHandler({
   return (err) => {
     if (allCapturedErrors) allCapturedErrors.push(err)
 
+    // A formatted error is already logged for this type of error
+    if (isBailoutToCSRError(err)) return
+
     // These errors are expected. We return the digest
     // so that they can be properly handled.
-    if (isDynamicUsageError(err)) {
-      return err.digest
-    }
+    if (isDynamicUsageError(err)) return err.digest
 
     // If the response was closed, we don't need to log the error.
     if (isAbortError(err)) return

packages/next/src/server/app-render/types.ts

@@ -142,7 +142,7 @@ export interface RenderOptsPartial {
   }
   params?: ParsedUrlQuery
   isPrefetch?: boolean
-  experimental: { ppr: boolean }
+  experimental: { ppr: boolean; missingSuspenseWithCSRBailout?: boolean }
   postponed?: string
 }
 

packages/next/src/server/async-storage/static-generation-async-storage-wrapper.ts

@@ -18,7 +18,7 @@ export type StaticGenerationContext = {
     isDraftMode?: boolean
     isServerAction?: boolean
     waitUntil?: Promise<any>
-    experimental: { ppr: boolean }
+    experimental: { ppr: boolean; missingSuspenseWithCSRBailout?: boolean }
 
     /**
      * A hack around accessing the store value outside the context of the

packages/next/src/server/config-schema.ts

@@ -369,6 +369,7 @@ export const configSchema: zod.ZodType<NextConfig> = z.lazy(() =>
         staticWorkerRequestDeduping: z.boolean().optional(),
         useWasmBinary: z.boolean().optional(),
         useLightningcss: z.boolean().optional(),
+        missingSuspenseWithCSRBailout: z.boolean().optional(),
       })
       .optional(),
     exportPathMap: z

packages/next/src/server/config-shared.ts

@@ -351,6 +351,16 @@ export interface ExperimentalConfig {
    * Use lightningcss instead of swc_css
    */
   useLightningcss?: boolean
+
+  /**
+   * Certain methods calls like `useSearchParams()` can bail out of server-side rendering of **entire** pages to client-side rendering,
+   * if they are not wrapped in a suspense boundary.
+   *
+   * When this flag is set to `true`, Next.js will break the build instead of warning, to force the developer to add a suspense boundary above the method call.
+   *
+   * @default false
+   */
+  missingSuspenseWithCSRBailout?: boolean
 }
 
 export type ExportPathMap = {
@@ -811,6 +821,7 @@ export const defaultConfig: NextConfig = {
         ? true
         : false,
     webpackBuildWorker: undefined,
+    missingSuspenseWithCSRBailout: false,
   },
 }
 

packages/next/src/shared/lib/lazy-dynamic/bailout-to-csr.ts

@@ -0,0 +1,14 @@
+// This has to be a shared module which is shared between client component error boundary and dynamic component
+
+const BAILOUT_TO_CSR = 'BAILOUT_TO_CLIENT_SIDE_RENDERING'
+
+/** An error that should be thrown when we want to bail out to client-side rendering. */
+export class BailoutToCSRError extends Error {
+  digest: typeof BAILOUT_TO_CSR = BAILOUT_TO_CSR
+}
+
+/** Checks if a passed argument is an error that is thrown if we want to bail out to client-side rendering. */
+export function isBailoutToCSRError(err: unknown): err is BailoutToCSRError {
+  if (typeof err !== 'object' || err === null) return false
+  return 'digest' in err && err.digest === BAILOUT_TO_CSR
+}

packages/next/src/shared/lib/lazy-dynamic/dynamic-bailout-to-csr.tsx

@@ -0,0 +1,21 @@
+'use client'
+
+import type { ReactElement } from 'react'
+import { BailoutToCSRError } from './bailout-to-csr'
+
+interface BailoutToCSRProps {
+  reason: string
+  children: ReactElement
+}
+
+/**
+ * If rendered on the server, this component throws an error
+ * to signal Next.js that it should bail out to client-side rendering instead.
+ */
+export function BailoutToCSR({ reason, children }: BailoutToCSRProps) {
+  if (typeof window === 'undefined') {
+    throw new BailoutToCSRError(reason)
+  }
+
+  return children
+}

packages/next/src/shared/lib/lazy-dynamic/dynamic-no-ssr.tsx

@@ -1,43 +1,45 @@
-import { Suspense, lazy, Fragment } from 'react'
-import { NoSSR } from './dynamic-no-ssr'
+import { Suspense, lazy } from 'react'
+import { BailoutToCSR } from './dynamic-bailout-to-csr'
 import type { ComponentModule } from './types'
 
 // Normalize loader to return the module as form { default: Component } for `React.lazy`.
 // Also for backward compatible since next/dynamic allows to resolve a component directly with loader
 // Client component reference proxy need to be converted to a module.
 function convertModule<P>(mod: React.ComponentType<P> | ComponentModule<P>) {
-  return { default: (mod as ComponentModule<P>)?.default || mod }
+  return { default: (mod as ComponentModule<P>)?.default ?? mod }
 }
 
-function Loadable(options: any) {
-  const opts = {
-    loader: null,
-    loading: null,
-    ssr: true,
-    ...options,
-  }
+const defaultOptions = {
+  loader: () => Promise.resolve(convertModule(() => null)),
+  loading: null,
+  ssr: true,
+}
 
-  const loader = () =>
-    opts.loader != null
-      ? opts.loader().then(convertModule)
-      : Promise.resolve(convertModule(() => null))
+interface LoadableOptions {
+  loader?: () => Promise<React.ComponentType<any> | ComponentModule<any>>
+  loading?: React.ComponentType<any> | null
+  ssr?: boolean
+}
 
-  const Lazy = lazy(loader)
+function Loadable(options: LoadableOptions) {
+  const opts = { ...defaultOptions, ...options }
+  const Lazy = lazy(() => opts.loader().then(convertModule))
   const Loading = opts.loading
-  const Wrap = opts.ssr ? Fragment : NoSSR
 
   function LoadableComponent(props: any) {
     const fallbackElement = Loading ? (
       <Loading isLoading={true} pastDelay={true} error={null} />
     ) : null
 
-    return (
-      <Suspense fallback={fallbackElement}>
-        <Wrap>
-          <Lazy {...props} />
-        </Wrap>
-      </Suspense>
+    const children = opts.ssr ? (
+      <Lazy {...props} />
+    ) : (
+      <BailoutToCSR reason="next/dynamic">
+        <Lazy {...props} />
+      </BailoutToCSR>
     )
+
+    return <Suspense fallback={fallbackElement}>{children}</Suspense>
   }
 
   LoadableComponent.displayName = 'LoadableComponent'