Skip internal routes in middleware

Author: devjiwonchoi

packages/next/src/build/entries.ts

@@ -45,6 +45,7 @@ import {
   isInstrumentationHookFilename,
 } from './utils'
 import { getPageStaticInfo } from './analysis/get-page-static-info'
+import { getDefaultMiddlewareMatcher } from '../shared/lib/router/utils/get-default-middleware-matcher'
 import { normalizePathSep } from '../shared/lib/page-path/normalize-path-sep'
 import { normalizePagePath } from '../shared/lib/page-path/normalize-page-path'
 import type { ServerRuntime } from '../types'
@@ -898,7 +899,7 @@ export async function createEntrypoints(
 
       if (isMiddlewareFile(page)) {
         middlewareMatchers = staticInfo.middleware?.matchers ?? [
-          { regexp: '.*', originalSource: '/:path*' },
+          getDefaultMiddlewareMatcher(params.config),
         ]
       }
 

packages/next/src/build/index.ts

@@ -150,6 +150,7 @@ import { isEdgeRuntime } from '../lib/is-edge-runtime'
 import { recursiveCopy } from '../lib/recursive-copy'
 import { lockfilePatchPromise, teardownTraceSubscriber } from './swc'
 import { getNamedRouteRegex } from '../shared/lib/router/utils/route-regex'
+import { getDefaultMiddlewareMatcher } from '../shared/lib/router/utils/get-default-middleware-matcher'
 import { getFilesInDir } from '../lib/get-files-in-dir'
 import { eventSwcPlugins } from '../telemetry/events/swc-plugins'
 import { normalizeAppPath } from '../shared/lib/router/utils/app-paths'
@@ -2580,10 +2581,7 @@ export default async function build(
           functionsConfigManifest.functions['/_middleware'] = {
             runtime: staticInfo.runtime,
             matchers: staticInfo.middleware?.matchers ?? [
-              {
-                regexp: '^.*$',
-                originalSource: '/:path*',
-              },
+              getDefaultMiddlewareMatcher(config),
             ],
           }
 

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

@@ -676,6 +676,7 @@ export const configSchema: zod.ZodType<NextConfig> = z.lazy(() =>
     serverExternalPackages: z.array(z.string()).optional(),
     serverRuntimeConfig: z.record(z.string(), z.any()).optional(),
     skipMiddlewareUrlNormalize: z.boolean().optional(),
+    skipMiddlewareNextInternalRoutes: z.boolean().optional(),
     skipTrailingSlashRedirect: z.boolean().optional(),
     staticPageGenerationTimeout: z.number().optional(),
     expireTime: z.number().optional(),

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

@@ -1236,6 +1236,12 @@ export interface NextConfig {
 
   skipMiddlewareUrlNormalize?: boolean
 
+  /**
+   * Skip Next.js internals route `/_next` from middleware.
+   * @default true
+   */
+  skipMiddlewareNextInternalRoutes?: boolean
+
   skipTrailingSlashRedirect?: boolean
 
   modularizeImports?: Record<
@@ -1515,6 +1521,7 @@ export const defaultConfig = Object.freeze({
   },
   htmlLimitedBots: undefined,
   bundlePagesRouterDependencies: false,
+  skipMiddlewareNextInternalRoutes: true,
 } satisfies NextConfig)
 
 export async function normalizeConfig(phase: string, config: any) {

packages/next/src/server/lib/router-utils/filesystem.ts

@@ -31,6 +31,7 @@ import { pathHasPrefix } from '../../../shared/lib/router/utils/path-has-prefix'
 import { normalizeLocalePath } from '../../../shared/lib/i18n/normalize-locale-path'
 import { removePathPrefix } from '../../../shared/lib/router/utils/remove-path-prefix'
 import { getMiddlewareRouteMatcher } from '../../../shared/lib/router/utils/middleware-route-matcher'
+import { getDefaultMiddlewareMatcher } from '../../../shared/lib/router/utils/get-default-middleware-matcher'
 import {
   APP_PATH_ROUTES_MANIFEST,
   BUILD_ID_FILE,
@@ -314,7 +315,7 @@ export async function setupFsCheck(opts: {
     } else if (functionsConfigManifest?.functions['/_middleware']) {
       middlewareMatcher = getMiddlewareRouteMatcher(
         functionsConfigManifest.functions['/_middleware'].matchers ?? [
-          { regexp: '.*', originalSource: '/:path*' },
+          getDefaultMiddlewareMatcher(opts.config),
         ]
       )
     }

packages/next/src/server/lib/router-utils/setup-dev-bundler.ts

@@ -48,6 +48,7 @@ import {
 } from '../../../shared/lib/constants'
 
 import { getMiddlewareRouteMatcher } from '../../../shared/lib/router/utils/middleware-route-matcher'
+import { getDefaultMiddlewareMatcher } from '../../../shared/lib/router/utils/get-default-middleware-matcher'
 
 import {
   isMiddlewareFile,
@@ -472,7 +473,7 @@ async function startWatcher(
             serverFields.actualMiddlewareFile
           )
           middlewareMatchers = staticInfo.middleware?.matchers || [
-            { regexp: '^/.*$', originalSource: '/:path*' },
+            getDefaultMiddlewareMatcher(opts.nextConfig),
           ]
           continue
         }

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

@@ -71,6 +71,7 @@ import type { LoadComponentsReturnType } from './load-components'
 import isError, { getProperError } from '../lib/is-error'
 import { splitCookiesString, toNodeOutgoingHttpHeaders } from './web/utils'
 import { getMiddlewareRouteMatcher } from '../shared/lib/router/utils/middleware-route-matcher'
+import { getDefaultMiddlewareMatcher } from '../shared/lib/router/utils/get-default-middleware-matcher'
 import { loadEnvConfig } from '@next/env'
 import { urlQueryToSearchParams } from '../shared/lib/router/utils/querystring'
 import { removeTrailingSlash } from '../shared/lib/router/utils/remove-trailing-slash'
@@ -1455,13 +1456,13 @@ export default class NextNodeServer extends BaseServer<
       const middlewareModule = await this.loadNodeMiddleware()
 
       if (middlewareModule) {
+        const matchers = middlewareModule.config?.matchers || [
+          getDefaultMiddlewareMatcher(this.nextConfig),
+        ]
         return {
-          match: getMiddlewareRouteMatcher(
-            middlewareModule.config?.matchers || [
-              { regexp: '.*', originalSource: '/:path*' },
-            ]
-          ),
+          match: getMiddlewareRouteMatcher(matchers),
           page: '/',
+          matchers,
         }
       }
 
@@ -1471,6 +1472,7 @@ export default class NextNodeServer extends BaseServer<
     return {
       match: getMiddlewareMatcher(middleware),
       page: '/',
+      matchers: middleware.matchers,
     }
   }
 
@@ -1679,6 +1681,7 @@ export default class NextNodeServer extends BaseServer<
       return { finished: false }
     }
 
+
     await this.ensureMiddleware(params.request.url)
     const middlewareInfo = this.getEdgeFunctionInfo({
       page: middleware.page,

packages/next/src/shared/lib/router/utils/get-default-middleware-matcher.ts

@@ -0,0 +1,20 @@
+import type { MiddlewareMatcher } from '../../../../build/analysis/get-page-static-info'
+
+export function getDefaultMiddlewareMatcher(config?: {
+  skipMiddlewareNextInternalRoutes?: boolean
+}): MiddlewareMatcher {
+  const skipInternal = config?.skipMiddlewareNextInternalRoutes !== false
+
+  if (skipInternal) {
+    // Match everything except /_next/* (but still match /_next/data/* because it is used for client navigation)
+    return {
+      regexp: '^(?!\\/_next\\/(?!data\\/)).*',
+      originalSource: '/:path*',
+    }
+  }
+
+  return {
+    regexp: '.*',
+    originalSource: '/:path*',
+  }
+}