refactor: add warning helper for removed experimental option

[SukkaW]

Continues #44202, implements #44202 (comment).

cc @styfle

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have a helpful link attached, see contributing.md

Feature

• Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• e2e tests added
• Documentation added
• Telemetry added. In case of a feature if it's used or not.
• Errors have a helpful link attached, see contributing.md

Documentation / Examples

• Make sure the linting passes by running pnpm build && pnpm lint
• The "examples guidelines" are followed from our contributing doc

[styfle]

I think the isCompilerFeature is too specific. Instead, we should be able to reference any part of the config.

Perhaps we could use a dot syntax like key: 'compiler.relay'

[SukkaW]

Done in 335c35a (#44213). But there will be no strict type check for oldKey and newKey.

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
buildDuration	36.5s	37.9s	⚠️ +1.4s
buildDurationCached	10.5s	10.6s	⚠️ +133ms
nodeModulesSize	95 MB	95 MB	✓
nextStartRea..uration (ms)	279ms	290ms	⚠️ +11ms

Client Bundles (main, webpack)

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
152-HASH.js gzip	64.5 kB	64.5 kB	✓
53.HASH.js gzip	182 B	182 B	✓
main-app-HASH.js gzip	205 B	205 B	✓
main-HASH.js gzip	79.2 kB	79.2 kB	✓
webpack-HASH.js gzip	1.7 kB	1.7 kB	✓
Overall change	146 kB	146 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
_app-HASH.js gzip	192 B	192 B	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	484 B	484 B	✓
css-HASH.js gzip	804 B	804 B	✓
dynamic-HASH.js gzip	2.29 kB	2.29 kB	✓
edge-ssr-HASH.js gzip	255 B	255 B	✓
head-HASH.js gzip	827 B	827 B	✓
hooks-HASH.js gzip	848 B	848 B	✓
image-HASH.js gzip	4.3 kB	4.3 kB	✓
index-HASH.js gzip	252 B	252 B	✓
link-HASH.js gzip	2.69 kB	2.69 kB	✓
routerDirect..HASH.js gzip	782 B	782 B	✓
script-HASH.js gzip	857 B	857 B	✓
withRouter-HASH.js gzip	781 B	781 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	15.6 kB	15.6 kB	✓

Client Build Manifests

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
_buildManifest.js gzip	481 B	481 B	✓
Overall change	481 B	481 B	✓

Rendered Page Sizes

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
index.html gzip	489 B	489 B	✓
link.html gzip	504 B	504 B	✓
withRouter.html gzip	485 B	485 B	✓
Overall change	1.48 kB	1.48 kB	✓

Edge SSR bundle Size

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
edge-ssr.js gzip	110 kB	110 kB	✓
page.js gzip	98.4 kB	98.4 kB	✓
Overall change	209 kB	209 kB	✓

Middleware size

	vercel/next.js canary	SukkaW/next.js load-config-deprecation-helper	Change
middleware-b..fest.js gzip	585 B	585 B	✓
middleware-r..fest.js gzip	145 B	145 B	✓
middleware.js gzip	27 kB	27 kB	✓
edge-runtime..pack.js gzip	1.83 kB	1.83 kB	✓
Overall change	29.6 kB	29.6 kB	✓

Diffs

Diff for page.js

@@ -8618,16 +8618,16 @@ Learn More: https://nextjs.org/docs/messages/node-module-in-edge-runtime`;
       /***/
     },
 
-    /***/ 199: /***/ (
+    /***/ 1036: /***/ (
       __unused_webpack_module,
       __unused_webpack_exports,
       __webpack_require__
     ) => {
       Promise.resolve(/* import() eager */).then(
-        __webpack_require__.bind(__webpack_require__, 2973)
+        __webpack_require__.bind(__webpack_require__, 1210)
       );
       Promise.resolve(/* import() eager */).then(
-        __webpack_require__.bind(__webpack_require__, 1210)
+        __webpack_require__.bind(__webpack_require__, 2973)
       );
       Promise.resolve(/* import() eager */).then(
         __webpack_require__.bind(__webpack_require__, 6448)

Diff for middleware-b..-manifest.js

@@ -9,7 +9,7 @@ self.__BUILD_MANIFEST = {
   rootMainFiles: [
     "static/chunks/webpack-c452a3e31b73f504.js",
     "static/chunks/152-4025b906f33b8271.js",
-    "static/chunks/main-app-ec4ed0640c5bbc2a.js"
+    "static/chunks/main-app-c9a0aaff35eafcb5.js"
   ],
   pages: {
     "/": [

Diff for main-app-HASH.js

@@ -1,16 +1,16 @@
 (self["webpackChunk_N_E"] = self["webpackChunk_N_E"] || []).push([
   [744],
   {
-    /***/ 9421: /***/ function(
+    /***/ 9915: /***/ function(
       __unused_webpack_module,
       __unused_webpack_exports,
       __webpack_require__
     ) {
       Promise.resolve(/* import() eager */).then(
-        __webpack_require__.t.bind(__webpack_require__, 1161, 23)
+        __webpack_require__.t.bind(__webpack_require__, 429, 23)
       );
       Promise.resolve(/* import() eager */).then(
-        __webpack_require__.t.bind(__webpack_require__, 429, 23)
+        __webpack_require__.t.bind(__webpack_require__, 1161, 23)
       );
       Promise.resolve(/* import() eager */).then(
         __webpack_require__.t.bind(__webpack_require__, 8138, 23)
@@ -28,7 +28,7 @@
       return __webpack_require__((__webpack_require__.s = moduleId));
     };
     /******/ __webpack_require__.O(0, [152], function() {
-      return __webpack_exec__(7070), __webpack_exec__(9421);
+      return __webpack_exec__(7070), __webpack_exec__(9915);
     });
     /******/ var __webpack_exports__ = __webpack_require__.O();
     /******/ _N_E = __webpack_exports__;

Commit: fc6b678

[styfle]

Instead of while and newKeys.shift(), could you use for (const key of newKeys)?

[SukkaW]

@styfle I was considering using for, but it can't stop before the last key.

Take compiler.relay (['compiler', 'relay']) as an example. We will need to stop at ['relay'], as only compiler requires current.compiler ||= {}. The last key relay requires current.relay = config.experimental.relay instead of current.relay ||= {}.

That's why I use while (.length > 1) here.

[styfle]

Thanks! Could you write a couple unit tests to ensure this is working as expected?

[SukkaW]

@styfle Sure! I just add the unit test in 672dfc7 (#44213).

[styfle]

I'm not seeing an option for allowMiddlewareResponseBody.

Where is that used?

[SukkaW]

Oh, my bad. allowMiddlewareResponseBody was removed in #44224. I must have missed it when rebasing my PR.
Fixed in 7e9482f (#44213).

[ijjk]

Looks good, thanks for the PR!