Drop the experimental env var for onRequestError API (#67856)

### What

Since the API is getting more stablized with few past iteration and it's
still under the experimental flag, it's good to ship as a API along with
the `instrumentation.js`

Author: huozhi

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

@@ -836,10 +836,7 @@ export default abstract class Server<
   ) {
     const [err, req, ctx] = args
 
-    if (
-      process.env.__NEXT_EXPERIMENTAL_INSTRUMENTATION &&
-      this.instrumentation
-    ) {
+    if (this.instrumentation) {
       try {
         await this.instrumentation.onRequestError?.(
           err,

packages/next/src/server/instrumentation/types.ts

@@ -23,3 +23,7 @@ export type InstrumentationModule = {
   register?(): void
   onRequestError?: InstrumentationOnRequestError
 }
+
+export namespace Instrumentation {
+  export type onRequestError = InstrumentationOnRequestError
+}

packages/next/src/server/web/globals.ts

@@ -37,12 +37,7 @@ export async function edgeInstrumentationOnRequestError(
 ) {
   const instrumentation = await getEdgeInstrumentationModule()
   try {
-    if (
-      process.env.__NEXT_EXPERIMENTAL_INSTRUMENTATION &&
-      instrumentation?.onRequestError
-    ) {
-      await instrumentation.onRequestError(...args)
-    }
+    await instrumentation?.onRequestError?.(...args)
   } catch (err) {
     // Log the soft error and continue, since the original error has already been thrown
     console.error('Error in instrumentation.onRequestError:', err)

packages/next/src/types.ts

@@ -38,6 +38,8 @@ export type {
   ResolvedViewport,
 } from './lib/metadata/types/metadata-interface'
 
+export type { Instrumentation } from './server/instrumentation/types'
+
 /**
  * Stub route type for typedRoutes before `next dev` or `next build` is run
  * @link https://nextjs.org/docs/app/building-your-application/configuring/typescript#statically-typed-links

test/e2e/on-request-error/basic/basic.test.ts

@@ -6,9 +6,6 @@ describe('on-request-error - basic', () => {
   const { next, skipped } = nextTestSetup({
     files: __dirname,
     skipDeployment: true,
-    env: {
-      __NEXT_EXPERIMENTAL_INSTRUMENTATION: '1',
-    },
   })
 
   if (skipped) {

test/e2e/on-request-error/basic/instrumentation.js renamed to test/e2e/on-request-error/basic/instrumentation.ts

@@ -1,8 +1,14 @@
-export function onRequestError(err, request, context) {
+import { type Instrumentation } from 'next'
+
+export const onRequestError: Instrumentation.onRequestError = (
+  err,
+  request,
+  context
+) => {
   fetch(`http://localhost:${process.env.PORT}/write-log`, {
     method: 'POST',
     body: JSON.stringify({
-      message: err.message,
+      message: (err as Error).message,
       request,
       context,
     }),

test/e2e/on-request-error/dynamic-routes/dynamic-routes.test.ts

@@ -6,9 +6,6 @@ describe('on-request-error - dynamic-routes', () => {
   const { next, skipped } = nextTestSetup({
     files: __dirname,
     skipDeployment: true,
-    env: {
-      __NEXT_EXPERIMENTAL_INSTRUMENTATION: '1',
-    },
   })
 
   if (skipped) {

test/e2e/on-request-error/server-action-error/server-action-error.test.ts

@@ -6,9 +6,6 @@ describe('on-request-error - server-action-error', () => {
   const { next, skipped } = nextTestSetup({
     files: __dirname,
     skipDeployment: true,
-    env: {
-      __NEXT_EXPERIMENTAL_INSTRUMENTATION: '1',
-    },
   })
 
   if (skipped) {

test/e2e/on-request-error/skip-next-internal-error/skip-next-internal-error.test.ts

@@ -4,9 +4,6 @@ describe('on-request-error - skip-next-internal-error', () => {
   const { next, skipped } = nextTestSetup({
     files: __dirname,
     skipDeployment: true,
-    env: {
-      __NEXT_EXPERIMENTAL_INSTRUMENTATION: '1',
-    },
   })
 
   if (skipped) {