Angular 20 build mangles class names

[wein2011]

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

19.2.14

Description

The name of the class provided by a ClassDecoratorContext is mangled in 20.0.0.

Unfortunately, this renders the new stage 3 class decorators useless.

Minimal Reproduction

1. Create an Angular sample application and add the following code to main.ts

export const setClassDef = () => (_target: unknown, context: ClassDecoratorContext) => {
  console.log(context.name);
};

@setClassDef()
export class MyClass {
}`

2. In tsconfig.json, set experimentalDecorators to false. This will allow the use of the new stage 3 decorators.
3. Install the packages
4. Serve the application with npm run start
5. Review the console output in the developer tools of the browser

I have attached a reproduction package:

code.zip

Exception or Error

When running with Angular 19.2.14, the output will show "MyClass2". This is the actual name of the class and a numeric suffix.

When running with Angular 20.0.0, the output will show "_a".

However, Angular 20.0.0 should also output "MyClass2".

Your Environment

Angular CLI: 20.0.0
Node: 22.16.0
Package Manager: npm 10.9.2
OS: win32 x64

Angular: 20.0.0
... build, cli, common, compiler, compiler-cli, core, forms
... platform-browser, router

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.2000.0
@angular-devkit/core         20.0.0
@angular-devkit/schematics   20.0.0
@schematics/angular          20.0.0
rxjs                         7.8.2
typescript                   5.8.3
zone.js                      0.15.1

Anything else relevant?

This could be related to the Vite/esbuild configuration for 20.0.0. for keepNames.

[JeanMeche]

This is due to the switch to baseline (see docs) in v20, with includes Safari 16.0 again.

If you generate a ng generate config browserslist and bump Safari/iOS to >= 16.4 you'll fix that issue.