Only resolve page runtime for react 18 and error on read failure (#35705

)

* Read the proper page file from either pages directory or from node_modules (inernal pages like _app, _document)
* Only reading page runtime when `reactRoot` is enabled, reduce time for react 17 apps

packages/next/build/entries.ts

@@ -1,4 +1,8 @@
-import type { PageRuntime, NextConfigComplete } from '../server/config-shared'
+import type {
+  PageRuntime,
+  NextConfigComplete,
+  NextConfig,
+} from '../server/config-shared'
 import type { webpack5 } from 'next/dist/compiled/webpack/webpack'
 import fs from 'fs'
 import chalk from 'next/dist/compiled/chalk'
@@ -105,8 +109,11 @@ const cachedPageRuntimeConfig = new Map<string, [number, PageRuntime]>()
 // could be thousands of pages existing.
 export async function getPageRuntime(
   pageFilePath: string,
-  globalRuntimeFallback?: 'nodejs' | 'edge'
+  nextConfig: Partial<NextConfig>
 ): Promise<PageRuntime> {
+  if (!nextConfig.experimental?.reactRoot) return undefined
+
+  const globalRuntime = nextConfig.experimental?.runtime
   const cached = cachedPageRuntimeConfig.get(pageFilePath)
   if (cached) {
     return cached[1]
@@ -118,6 +125,7 @@ export async function getPageRuntime(
       encoding: 'utf8',
     })
   } catch (err) {
+    if (process.env.NODE_ENV === 'production') throw err
     return undefined
   }
 
@@ -183,7 +191,7 @@ export async function getPageRuntime(
 
   if (!pageRuntime) {
     if (isRuntimeRequired) {
-      pageRuntime = globalRuntimeFallback
+      pageRuntime = globalRuntime
     }
   }
 
@@ -217,6 +225,7 @@ export async function createEntrypoints(
   const hasRuntimeConfig =
     Object.keys(config.publicRuntimeConfig).length > 0 ||
     Object.keys(config.serverRuntimeConfig).length > 0
+  const hasReactRoot = !!config.experimental.reactRoot
 
   const defaultServerlessOptions = {
     absoluteAppPath: pages['/_app'],
@@ -242,11 +251,9 @@ export async function createEntrypoints(
       'base64'
     ),
     i18n: config.i18n ? JSON.stringify(config.i18n) : '',
-    reactRoot: config.experimental.reactRoot ? 'true' : '',
+    reactRoot: hasReactRoot ? 'true' : '',
   }
 
-  const globalRuntime = config.experimental.runtime
-
   await Promise.all(
     Object.keys(pages).map(async (page) => {
       const absolutePagePath = pages[page]
@@ -260,11 +267,12 @@ export async function createEntrypoints(
       const isReserved = isReservedPage(page)
       const isCustomError = isCustomErrorPage(page)
       const isFlight = isFlightPage(config, absolutePagePath)
-      const isEdgeRuntime =
-        (await getPageRuntime(
-          join(pagesDir, absolutePagePath.slice(PAGES_DIR_ALIAS.length + 1)),
-          globalRuntime
-        )) === 'edge'
+      const isInternalPages = !absolutePagePath.startsWith(PAGES_DIR_ALIAS)
+      const pageFilePath = isInternalPages
+        ? require.resolve(absolutePagePath)
+        : join(pagesDir, absolutePagePath.replace(PAGES_DIR_ALIAS, ''))
+      const pageRuntime = await getPageRuntime(pageFilePath, config)
+      const isEdgeRuntime = pageRuntime === 'edge'
 
       if (page.match(MIDDLEWARE_ROUTE)) {
         const loaderOpts: MiddlewareLoaderOptions = {

packages/next/build/index.ts

@@ -971,13 +971,9 @@ export default async function build(
                 p.startsWith(actualPage + '.') ||
                 p.startsWith(actualPage + '/index.')
             )
-            const pageRuntime =
-              hasConcurrentFeatures && pagePath
-                ? await getPageRuntime(
-                    join(pagesDir, pagePath),
-                    config.experimental.runtime
-                  )
-                : undefined
+            const pageRuntime = pagePath
+              ? await getPageRuntime(join(pagesDir, pagePath), config)
+              : undefined
 
             if (
               !isMiddlewareRoute &&

packages/next/server/dev/hot-reloader.ts

@@ -509,7 +509,7 @@ export default class HotReloader {
 
             const pageRuntimeConfig = await getPageRuntime(
               absolutePagePath,
-              this.runtime
+              this.config
             )
             const isEdgeSSRPage = pageRuntimeConfig === 'edge' && !isApiRoute
 

packages/next/server/dev/next-dev-server.ts

@@ -285,7 +285,7 @@ export default class DevServer extends Server {
           invalidatePageRuntimeCache(fileName, safeTime)
           const pageRuntimeConfig = await getPageRuntime(
             fileName,
-            this.nextConfig.experimental.runtime
+            this.nextConfig
           )
           const isEdgeRuntime = pageRuntimeConfig === 'edge'
 

packages/next/server/dev/on-demand-entry-handler.ts

@@ -207,7 +207,7 @@ export default function onDemandEntryHandler(
       const isApiRoute = normalizedPage.match(API_ROUTE) && !isMiddleware
       const pageRuntimeConfig = await getPageRuntime(
         absolutePagePath,
-        nextConfig.experimental.runtime
+        nextConfig
       )
       const isEdgeServer = pageRuntimeConfig === 'edge'
 

test/unit/parse-page-runtime.test.ts

@@ -1,26 +1,36 @@
 import { getPageRuntime } from 'next/dist/build/entries'
+import type { PageRuntime } from 'next/dist/server/config-shared'
 import { join } from 'path'
 
 const fixtureDir = join(__dirname, 'fixtures')
 
+function createNextConfig(runtime?: PageRuntime) {
+  return {
+    experimental: { reactRoot: true, runtime },
+  }
+}
+
 describe('parse page runtime config', () => {
   it('should parse nodejs runtime correctly', async () => {
     const runtime = await getPageRuntime(
-      join(fixtureDir, 'page-runtime/nodejs.js')
+      join(fixtureDir, 'page-runtime/nodejs.js'),
+      createNextConfig()
     )
     expect(runtime).toBe('nodejs')
   })
 
   it('should parse edge runtime correctly', async () => {
     const runtime = await getPageRuntime(
-      join(fixtureDir, 'page-runtime/edge.js')
+      join(fixtureDir, 'page-runtime/edge.js'),
+      createNextConfig()
     )
     expect(runtime).toBe('edge')
   })
 
   it('should return undefined if no runtime is specified', async () => {
     const runtime = await getPageRuntime(
-      join(fixtureDir, 'page-runtime/static.js')
+      join(fixtureDir, 'page-runtime/static.js'),
+      createNextConfig()
     )
     expect(runtime).toBe(undefined)
   })
@@ -30,15 +40,15 @@ describe('fallback to the global runtime configuration', () => {
   it('should fallback when gSP is defined and exported', async () => {
     const runtime = await getPageRuntime(
       join(fixtureDir, 'page-runtime/fallback-with-gsp.js'),
-      'edge'
+      createNextConfig('edge')
     )
     expect(runtime).toBe('edge')
   })
 
   it('should fallback when gSP is re-exported from other module', async () => {
     const runtime = await getPageRuntime(
       join(fixtureDir, 'page-runtime/fallback-re-export-gsp.js'),
-      'edge'
+      createNextConfig('edge')
     )
     expect(runtime).toBe('edge')
   })