incorrect detection of zoneless app

[DibyodyutiMondal]

Command

build

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

Including any js/ts file in the polyfills array causes the angular server to incorrectly identify the app as a non-zoneless app. Thus it tries to include zone.js, which is deleted, because I uninstall the package as per the guide.

Minimal Reproduction

Exception or Error

Your Environment

Angular CLI: 20.1.0
Node: 22.14.0
Package Manager: pnpm 10.13.1
OS: linux x64

Angular: 20.1.0
... animations, build, cdk, cli, common, compiler, compiler-cli
... core, forms, language-service, material
... material-luxon-adapter, platform-browser
... platform-browser-dynamic, platform-server, router, ssr

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.2001.0
@angular-devkit/build-angular   20.1.0
@angular-devkit/core            20.1.0
@angular-devkit/schematics      20.1.0
@schematics/angular             20.0.6
ng-packagr                      20.0.1
rxjs                            7.8.1
typescript                      5.8.3

Anything else relevant?

TLDR

This is essentially a re-open of #28898. Developers are forced to avoid adding any js/ts file to the polyfills array. Instead, they have to create js scripts inline inside index.html, or write js files, and include them as assets with index.html

---

The problem is within these lines:

angular-cli/packages/angular/build/src/tools/esbuild/utils.ts

Lines 469 to 478 in 2c3a46b

	/**
	* Ascertain whether the application operates without `zone.js`, we currently rely on the polyfills setting to determine its status.
	* If a file with an extension is provided or if `zone.js` is included in the polyfills, the application is deemed as not zoneless.
	* @param polyfills An array of polyfills
	* @returns true, when the application is considered as zoneless.
	*/
	export function isZonelessApp(polyfills: string[] | undefined): boolean {
	// TODO: Instead, we should rely on the presence of zone.js in the polyfills build metadata.
	return !polyfills?.some((p) => p === 'zone.js' || /\.[mc]?[jt]s$/.test(p));
	}

The presence of any js/ts file in the polyfills array causes zone to be included, even though I uninstalled zone.js and do everything zone-less-ly.

I had a file called polyfill-buffer.ts which I used to add to the polyfill array:

import { Buffer } from 'buffer';

if (!globalThis.Buffer) {
  Object.assign(globalThis, { Buffer });
}

Now I have to add it to index.html as a script

import { Buffer } from 'https://cdn.jsdelivr.net/npm/buffer/+esm';

if (!globalThis.Buffer) {
  Object.assign(globalThis, { Buffer });
}

This is maintainable for small scripts like these. But it eliminates the possibility of using any file-based polyfill stuff.