Add style preprocessor option to disable deprecation warnings in Sass for V19

[L-X-T]

Which @angular/* package(s) are relevant/related to the feature request?

No response

Description

After updating @angular to v19, I’ve encountered a ton SCSS compiler deprecation warnings across many of my Angular projects. This issue occurs because the “sass” dependency in @angular/build/package.json was updated from “1.77.6” to “1.80.6”. As a temporary workaround, I reverted this dependency to “1.77.6” in the project’s node_modules directory, although this is - quite obvious - not ideal.

Ideally, we should remove deprecated SCSS code in our scss files and 3rd party dependencies (this is where it becomes a nightmare). However, as a temporary solution to silence these deprecation warnings and be relieved when running “ng s“, it would be helpful to pass a “stylePreprocessorOptions” (already exists) flag via “angular.json“ into the Sass compiler.

Please note that in Nuxt/Vite and Ember, disabling these deprecation warnings is already possible, see here and here.

Proposed solution

Additional option in “angular.json". (Should default to false.)

"stylePreprocessorOptions": {
  "silenceDeprecations": true
},

This should result in passing the flag "--quiet-deps" to the sass compiler. How to silence this warnings internally can be learned here: https://sass-lang.com/documentation/breaking-changes/mixed-decls/#silencing-deprecations-in-dependencies

Alternatives considered

Downgrade sass dep to “1.77.6“.

[JeanMeche]

Hi Alex !
Have you seen the changes introduced by #28627 ?

[L-X-T]

Oops. No, sorry, I did not find that in my search.

[L-X-T]

Okay, thanks to @JeanMeche ❤️ and some extra googleing, I found this setting to do the job for me:

"stylePreprocessorOptions": {
  "sass": {
    "silenceDeprecations": ["mixed-decls", "color-functions", "global-builtin", "import"]
  }
},

So the is already implemented and working :-)

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