Angular sourceLocale not compatible with SSR and Native Federation

[M4R1KU]

With what library do you have an issue?

native-federation

Reproduction of the bug/regression with instructions

https://github.com/M4R1KU/nf-ssr-locales
(Changes in this commit: M4R1KU/nf-ssr-locales@84dd0e5)

ng build shell
ng build mfe1

npm run serve:ssr:shell
npm run serve:ssr:mfe1

Open http://localhost:4200

---

Opening the console shows the following error:

Uncaught TypeError: The specifier “@angular/common/locales/global/de-CH” was a bare specifier, but was not remapped to anything. Relative module specifiers must start with “./”, “../” or “/”.

The locales are imported through the polyfills and the corresponding import is automatically added by the angular build process when the projects.<project-name>.i18n.sourceLocale property is set in angular.json

Through debugging the options passed to the angular builder and then subsequently esbuild, I am pretty sure that this is the problematic line.

When the externalDependencies property is set on the build options (i.e. "ssr": true in angular.json), I observe in the angular-locale-data plugin that the import to @angular/common/locales/global/* is considered to be external (here).
If ssr is set to false in the options of the @angular-architects/native-federation:build builder, this is not the case and the locale data is bundled into the polyfills.js output.

Expected behavior

I would expect the polyfills output file to always include the bundled locale data if it is set through the sourceLocale property in angular.json.

Versions of Native/Module Federation, Angular, Node, Browser, and operating system

Native Federation: 20.1.7
Angular: 20.3.7
Node: 22.19.0
Browser: Firefox 143.0.4
Operating System: Linux 6.17.1-arch1-1

Other information

Start of polyfills when ssr: true (contains plain import)

import"@angular/common/locales/global/de-CH";var ot=globalThis;function Je(o){return(ot.__Zone_symbol_prefix||"__zone_symbol__")+o}function os(){let o= ........

Start of polyfills when ssr: false (contains bundled locales)

(function(s){s.ng??={},s.ng.common??={},s.ng.common.locales??={};let o=void 0;function y(a){let p=a,S=Math.floor(Math.abs(a)),I=a.toString().replace(/^[^.]*\.?/,"").length;return S===1&&I===0?1:5}s.ng.common.locales["de-ch"]=["de-CH",[["AM","PM"]],o,[["S","M", ........

I would be willing to submit a PR to fix this issue

• Yes
• No

[Aukevanoost]

I have been digging a bit in the issue but no luck yet.

Here's what I know: The externalDependencies can indeed be problematic, since it's been passed to ESbuild which esbuild is treating as wildcard. The list includes "@angular/common".

This means that --external:@foo/bar implicitly also means --external:@foo/bar/* which matches the import path @foo/bar/baz. So it marks all paths inside the @foo/bar package as external too.
src: https://esbuild.github.io/api/#external

I rarely use SSR so I personally have no idea why the if statement was added in the first place. It came with the "transient" flag feature which is now deprecated so maybe this is too? We'll have to experiment
src: commit