Karma esbuild builder stack trace sourcemap reference `dist/test-out`

[cexbrayat]

Command

test

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

When using the @angular/build:karma builder, a test in error will show the following sourcemap:

at dist/test-out/29ed73c2-b781-409d-a89d-bfa4055a0227/src/app/app.component.spec.ts:20:23

instead of referencing src/app.component.spec.ts:17:34 which allows to click it and open it directly in the IDE.

Minimal Reproduction

Run:

npx @angular/cli@20.0.0-next.0 new karma-sourcemap --defaults --no-routing

Edit app.component.spec.ts to make a test fail and run ng test:

Chrome 133.0.0.0 (Mac OS 10.15.7) AppComponent should have the 'karma-sourcemap' title FAILED
        Expected 'karma-sourcemap' to equal 'other'.
            at <Jasmine>
            at UserContext.<anonymous> (dist/test-out/29ed73c2-b781-409d-a89d-bfa4055a0227/src/app/app.component.spec.ts:20:23)

Exception or Error

Your Environment

Angular CLI: 20.0.0-next.0
Node: 20.18.3
Package Manager: npm 10.9.0
OS: darwin arm64

Angular: 20.0.0-next.1
... common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.2000.0-next.0
@angular-devkit/core         20.0.0-next.0
@angular-devkit/schematics   20.0.0-next.0
@angular/build               20.0.0-next.0
@angular/cli                 20.0.0-next.0
@schematics/angular          20.0.0-next.0
rxjs                         7.8.2
typescript                   5.8.2
zone.js                      0.15.0

Anything else relevant?

No response

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