extract-i18n does not extract message from files loaded only server side

在連結的重現應用程式中執行 extract-i18n，並將其輸出與 server-service.service.ts 中的訊息進行比較。追蹤該命令如何發現不直接相依於 app.module 或瀏覽器端程式碼的檔案。當伺服器端服務中的訊息包含在擷取輸出中時，即表示完成。

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• [x ] extract-i18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes, the previous version in which this bug was not present was: ....

Description

The extraction tool does not process files that do not have a direct dependency on the app.module, or, generally, on the browser side.
In my case an abstract service is replaced by two versions of the service, one browser side, the other server side. The server-side one is ignored during the extraction process.

🔬 Minimal Reproduction

I made a simple repro app that reproduce the problem.
Just run extract-i18n to see that message in server-service.service.ts is ignored.

🔥 Exception or Error

🌍 Your Environment

Angular: 12.0.1
... animations, cdk, cli, common, compiler, compiler-cli, core
... forms, language-service, material, platform-browser
... platform-browser-dynamic, platform-server, router
... service-worker

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.1200.5
@angular-devkit/build-angular     12.0.5
@angular-devkit/build-optimizer   0.1200.5
@angular-devkit/core              12.0.1
@angular-devkit/schematics        12.0.1
@angular/flex-layout              12.0.0-beta.34
@angular/localize                 12.0.5
@nguniversal/builders             12.1.3
@nguniversal/common               12.0.0
@nguniversal/express-engine       12.0.0
@schematics/angular               12.0.1
rxjs                              7.4.0
typescript                        4.2.4

Anything else relevant?