Throw an error if client builds retain references to `*.server.ts` files

[AndrewKushnir]

Command

build

Description

When SSR is enabled in an Angular project, there are a few .server.ts files produced (e.g. app.config.server.ts). The .server.ts suffix is also used by different applications as a way to structure and separate client and server code.

The proposal is to update the build pipeline to throw an error in case files with .server.ts suffix are present in the final client build output.

// cc @alan-agius4