Remove React 17 logic from Pages Router static generation (#82604)

`allReady` is available in all supported React versions so we can remove the conditional check.  The helper type can be replaced with the actual type from React.

Author: eps1lon

packages/next/src/server/render.tsx

@@ -1,5 +1,6 @@
 import type { IncomingMessage, ServerResponse } from 'http'
 import type { ParsedUrlQuery } from 'querystring'
+import type { ReactDOMServerReadableStream } from 'react-dom/server'
 import type { NextRouter } from '../shared/lib/router/router'
 import type { HtmlProps } from '../shared/lib/html-context.shared-runtime'
 import type { DomainLocale } from './config'
@@ -30,7 +31,6 @@ import type {
   SizeLimit,
 } from '../types'
 import type { UnwrapPromise } from '../lib/coalesced-function'
-import type { ReactReadableStream } from './stream-utils/node-web-streams-helper'
 import type { ClientReferenceManifest } from '../build/webpack/plugins/flight-manifest-plugin'
 import type { NextFontManifest } from '../build/webpack/plugins/next-font-manifest-plugin'
 import type { PagesModule } from './route-modules/pages/module'
@@ -1305,7 +1305,7 @@ export async function renderToHTMLImpl(
       renderShell: (
         _App: AppType,
         _Component: NextComponentType
-      ) => Promise<ReactReadableStream>
+      ) => Promise<ReactDOMServerReadableStream>
     ) {
       const renderPage: RenderPage = async (
         options: ComponentsEnhancer = {}

packages/next/src/server/stream-utils/node-web-streams-helper.ts

@@ -1,3 +1,4 @@
+import type { ReactDOMServerReadableStream } from 'react-dom/server'
 import { getTracer } from '../lib/trace/tracer'
 import { AppRenderSpan } from '../lib/trace/constants'
 import { DetachedPromise } from '../../lib/detached-promise'
@@ -17,10 +18,6 @@ function voidCatch() {
   // and be unhandled
 }
 
-export type ReactReadableStream = ReadableStream<Uint8Array> & {
-  allReady?: Promise<void> | undefined
-}
-
 // We can share the same encoder instance everywhere
 // Notably we cannot do the same for TextDecoder because it is stateful
 // when handling streaming data
@@ -221,7 +218,7 @@ export function renderToInitialFizzStream({
   }
   element: React.ReactElement
   streamOptions?: Parameters<typeof ReactDOMServer.renderToReadableStream>[1]
-}): Promise<ReactReadableStream> {
+}): Promise<ReactDOMServerReadableStream> {
   return getTracer().trace(AppRenderSpan.renderToReadableStream, async () =>
     ReactDOMServer.renderToReadableStream(element, streamOptions)
   )
@@ -678,7 +675,7 @@ export type ContinueStreamOptions = {
 }
 
 export async function continueFizzStream(
-  renderStream: ReactReadableStream,
+  renderStream: ReactDOMServerReadableStream,
   {
     suffix,
     inlinedDataStream,
@@ -693,9 +690,8 @@ export async function continueFizzStream(
   // Suffix itself might contain close tags at the end, so we need to split it.
   const suffixUnclosed = suffix ? suffix.split(CLOSE_TAG, 1)[0] : null
 
-  // If we're generating static HTML and there's an `allReady` promise on the
-  // stream, we need to wait for it to resolve before continuing.
-  if (isStaticGeneration && 'allReady' in renderStream) {
+  // If we're generating static HTML we need to wait for it to resolve before continuing.
+  if (isStaticGeneration) {
     await renderStream.allReady
   }