Angular package executor creates sourcemaps that cause extract-i18n to crash

[daiscog]

Current Behavior

Reopening #32586 as I've since narrowed this down to an issue with the build output of the @nx/angular:package executor.

Given:

• I have a publishable Angular library that uses $localize
• I build that with the @nx/angular:package executor then publish/pack the result
• I install the built package in another Angular (or nx) workspace and consume it in my app

Then when I run ng extract-i18n (or nx extract-i18n) for the app, the process crashes with the following error:

[error] TypeError: Cannot read properties of undefined (reading 'startOfLinePositions')
    at MessageExtractor.getOriginalLocation (file:///.../node_modules/@angular/localize/tools/bundles/chunk-TZHZOBVD.js:183:41)
    ...

After first raising an issue with Angular at angular/angular#64379 I've since done some more digging and have found that the issue occurs when the source maps in the package contain a comment at the end of each sourcesContent entry like so:

//# sourceMappingURL=data:application/json;base64,ey...

If I delete this comment from the sourcemaps, delete the .angular cache, then rerun ng extract-i18n the process completes successfully.

Libraries built with @nx/angular:package version 20.8.2 do not result in this extra comment and therefore work just fine. We've found the problem after upgrading to nx 21.6.3 and Angular 20.

Also, to verify it's a problem with the @nx/angular:package executor and not (for example) tsconfig or similar, I've replaced the executor with Angular's native @angular/build:ng-packagr builder (no other config changes at all) and rebuilt the lib - the output of this builder does not include the sourceMappingURL=data:... comment in the source maps and when packaged and consumed in the app, the extract-i18n command completes successfully.

I'm therefore reopening as it could be argued that the issue is a regression in the @nx/angular:package executor as it's producing content the Angular CLI cannot handle.

Expected Behavior

I can build and publish an Angular library with the @nx/angular:package executor, consume that in another app, and successfully run extract-i18n in that app.

Nx Report

Node           : 22.14.0
OS             : darwin-arm64
Native Target  : aarch64-macos
npm            : 10.9.2

nx                     : 21.6.3
@nx/js                 : 21.6.3
@nx/jest               : 21.6.3
@nx/eslint             : 21.6.3
@nx/workspace          : 21.6.3
@nx/angular            : 21.6.3
@nx/cypress            : 21.6.3
@nx/devkit             : 21.6.3
@nx/eslint-plugin      : 21.6.3
@nx/module-federation  : 21.6.3
@nx/node               : 21.6.3
@nx/playwright         : 21.6.3
@nx/plugin             : 21.6.3
@nx/rollup             : 20.8.2
@nx/rspack             : 21.6.3
@nx/web                : 21.6.3
@nx/webpack            : 21.6.3
@nx/docker             : 21.6.3
nx-cloud               : 19.1.0
@nrwl/nx-cloud         : 19.1.0
typescript             : 5.9.3

---------------------------------------
Registered Plugins:
@nx/jest/plugin
---------------------------------------
Community plugins:
@ng-bootstrap/ng-bootstrap : 19.0.1
@ngneat/spectator          : 19.6.2
@ngrx/component            : 20.0.1
@ngrx/component-store      : 20.0.1
@ngrx/effects              : 20.0.1
@ngrx/entity               : 20.0.1
@ngrx/operators            : 20.0.1
@ngrx/router-store         : 20.0.1
@ngrx/schematics           : 20.0.1
@ngrx/signals              : 20.0.1
@ngrx/store                : 20.0.1
@ngrx/store-devtools       : 20.0.1
@nx/azure-cache            : 4.0.0
angular-eslint             : 20.3.0
ng-mocks                   : 14.13.5
nx-stylelint               : 17.1.5
---------------------------------------
Local workspace plugins:
---------------------------------------
Cache Usage: 669.95 KB / 92.64 GB
---------------------------------------

Operating System

• macOS
• Linux
• Windows
• Other (Please specify)

[daiscog]

🤔 I've tried stepping through nx migrations one minor version at a time from 21.0.0 onwards. I first see the //# sourceMappingURL comment in the sourcemap after migrating to 21.2.0 (which also migrates from Angular 19 to 20).

However, if I revert then migrate to nx 21.2.0 using --interactive to opt-out of the Angular migration I no longer see the //# sourceMappingURL comment in the built sourcemap.

However, if (as noted above) I then replace the @nx/angular:package executor with @angular-devkit/build-angular:ng-packagr and rebuild, the problematic comment in the sourcemap goes away again. So it's not Angular alone that's the problem but a combination of using the @nx/angular:package executor with Angular 20.

[daiscog]

Update

The executor @nx/angular:ng-packagr-lite does not have the same problem so we can switch to using that to build our libs as a workaround.

As an aside, it looks like the difference between the two executors is that package rolls up the build result into a single flat fesm format, whereas ng-packagr-lite produces multiple esm files. It's not immediately clear to me from the documentation why one would opt for one executor over the other. It seems when the packaged libraries in either format are installed in another Angular project, the consuming app builds just fine either way. So for now we'll switch to ng-packagr-lite but it would be great if there were some guidance from nx about the pros and cons of each executor and in which situations one should prefer each one over the other.