Update middleware eval checks

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

@@ -514,7 +514,13 @@ export default class DevServer extends Server {
     parsed: UrlWithParsedQuery
   }): Promise<FetchEventResult | null> {
     try {
-      const result = await super.runMiddleware(params)
+      const result = await super.runMiddleware({
+        ...params,
+        onWarning: (warn) => {
+          this.logErrorWithOriginalStack(warn, 'warning', 'client')
+        },
+      })
+
       result?.waitUntil.catch((error) =>
         this.logErrorWithOriginalStack(error, 'unhandledRejection', 'client')
       )
@@ -589,7 +595,7 @@ export default class DevServer extends Server {
 
   private async logErrorWithOriginalStack(
     err?: unknown,
-    type?: 'unhandledRejection' | 'uncaughtException',
+    type?: 'unhandledRejection' | 'uncaughtException' | 'warning',
     stats: 'server' | 'client' = 'server'
   ) {
     let usedOriginalStack = false
@@ -630,11 +636,15 @@ export default class DevServer extends Server {
             const { file, lineNumber, column, methodName } = originalStackFrame
 
             console.error(
-              chalk.red('error') +
+              (type === 'warning' ? chalk.yellow('warn') : chalk.red('error')) +
                 ' - ' +
                 `${file} (${lineNumber}:${column}) @ ${methodName}`
             )
-            console.error(`${chalk.red(err.name)}: ${err.message}`)
+            console.error(
+              `${(type === 'warning' ? chalk.yellow : chalk.red)(err.name)}: ${
+                err.message
+              }`
+            )
             console.error(originalCodeFrame)
             usedOriginalStack = true
           }
@@ -647,7 +657,9 @@ export default class DevServer extends Server {
     }
 
     if (!usedOriginalStack) {
-      if (type) {
+      if (type === 'warning') {
+        Log.warn(err + '')
+      } else if (type) {
         Log.error(`${type}:`, err + '')
       } else {
         Log.error(err + '')

packages/next/server/next-server.ts

@@ -611,6 +611,7 @@ export default class Server {
     response: ServerResponse
     parsedUrl: ParsedNextUrl
     parsed: UrlWithParsedQuery
+    onWarning?: (warning: Error) => void
   }): Promise<FetchEventResult | null> {
     this.middlewareBetaWarning()
 
@@ -672,6 +673,12 @@ export default class Server {
             page: page,
           },
           ssr: !!this.nextConfig.experimental.concurrentFeatures,
+          onWarning: (warning: Error) => {
+            if (params.onWarning) {
+              warning.message += ` "./${middlewareInfo.name}"`
+              params.onWarning(warning)
+            }
+          },
         })
 
         for (let [key, value] of result.response.headers) {

packages/next/server/web/sandbox/sandbox.ts

@@ -10,6 +10,7 @@ import vm from 'vm'
 let cache:
   | {
       context: { [key: string]: any }
+      onWarning: (warn: Error) => void
       paths: Map<string, string>
       require: Map<string, any>
       sandbox: vm.Context
@@ -34,6 +35,7 @@ export function clearSandboxCache(path: string, content: Buffer | string) {
 
 export async function run(params: {
   name: string
+  onWarning: (warn: Error) => void
   paths: string[]
   request: RequestData
   ssr: boolean
@@ -91,6 +93,7 @@ export async function run(params: {
 
     cache = {
       context,
+      onWarning: params.onWarning,
       paths: new Map<string, string>(),
       require: new Map<string, any>([
         [require.resolve('next/dist/compiled/cookie'), { exports: cookie }],
@@ -121,6 +124,8 @@ export async function run(params: {
         map: { Request: 'Request' },
       },
     ])
+  } else {
+    cache.onWarning = params.onWarning
   }
 
   for (const paramPath of params.paths) {
@@ -233,12 +238,13 @@ function isRequestLike(obj: unknown): obj is Request {
 function __next_eval__(fn: Function) {
   const key = fn.toString()
   if (!cache?.warnedEvals.has(key)) {
-    console.warn(
-      new Error(
-        `Dynamic Code Evaluation (e. g. 'eval', 'new Function') not allowed in Middleware`
-      ).stack
+    const warning = new Error(
+      `Dynamic Code Evaluation (e. g. 'eval', 'new Function') not allowed in Middleware`
     )
+    warning.name = 'DynamicCodeEvaluationWarning'
+    Error.captureStackTrace(warning, __next_eval__)
     cache?.warnedEvals.add(key)
+    cache?.onWarning(warning)
   }
   return fn()
 }

test/integration/middleware/with-eval/test/index.test.js

@@ -1,12 +1,14 @@
 /* eslint-env jest */
 
+import stripAnsi from 'next/dist/compiled/strip-ansi'
 import { join } from 'path'
 import {
   fetchViaHTTP,
   findPort,
   killApp,
   launchApp,
   nextBuild,
+  waitFor,
 } from 'next-test-utils'
 
 const context = {}
@@ -22,6 +24,7 @@ describe('Middleware usage of dynamic code evaluation', () => {
     beforeAll(async () => {
       context.appPort = await findPort()
       context.app = await launchApp(context.appDir, context.appPort, {
+        env: { __NEXT_TEST_WITH_DEVTOOL: 1 },
         onStdout(msg) {
           output += msg
         },
@@ -37,13 +40,20 @@ describe('Middleware usage of dynamic code evaluation', () => {
     it('shows a warning when running code with eval', async () => {
       const res = await fetchViaHTTP(context.appPort, `/using-eval`)
       const json = await res.json()
+      await waitFor(500)
       expect(json.value).toEqual(100)
       expect(output).toContain(DYNAMIC_CODE_ERROR)
+      expect(output).toContain('DynamicCodeEvaluationWarning')
+      expect(output).toContain('pages/_middleware')
+      expect(output).toContain('lib/utils.js')
+      expect(output).toContain('usingEval')
+      expect(stripAnsi(output)).toContain("value: eval('100')")
     })
 
     it('does not show warning when no code uses eval', async () => {
       const res = await fetchViaHTTP(context.appPort, `/not-using-eval`)
       const json = await res.json()
+      await waitFor(500)
       expect(json.value).toEqual(100)
       expect(output).not.toContain(DYNAMIC_CODE_ERROR)
     })
@@ -61,6 +71,8 @@ describe('Middleware usage of dynamic code evaluation', () => {
 
     it('should have middleware warning during build', () => {
       expect(buildResult.stderr).toContain(`Failed to compile`)
+      expect(buildResult.stderr).toContain(`Used by usingEval`)
+      expect(buildResult.stderr).toContain(`./pages/_middleware.js`)
       expect(buildResult.stderr).toContain(DYNAMIC_CODE_ERROR)
     })
   })