[svelte-check] cannot force color output

[marekdedic]

Describe the bug

Hi, I am running svelte-check with npm-run-all with output aggregation. This normally removes color support (as it probably should), but I would like to force svelte-check to output colors...

Reproduction

{
  "scripts": {
    "lint:svelte-check": "svelte-check",
    "lint": "run-p --aggregate-output lint:*"
  }
}

Expected behaviour

I'd expect the following to be the same:

npm run lint:svelte-check:

npm run lint:

System Info

• OS: Ubuntu 24.04
• Shell: zsh

Which package is the issue about?

svelte-check

Additional Information, eg. Screenshots

I also tried FORCE_COLOR=1, but that gives an in-between result with some colors. I think it's great to support thing like NO_COLOR, but my suggestion would be to add --color that enables colored output as well.

FORCE_COLOR=1 npm run lint:

[jasonlyu123]

The colouring of the error message for the Sass compiler comes directly from the Sass compiler. So it's out of svelte-check's control. I did some digging and it seems like sass only supports --color while sass-embbed support the FORCE_COLOR variable. Can you check if you were using sass and check if it works if you install sass-embbed?

[marekdedic]

Thanks for the response, sass-embedded doesn't work for me, the results is the same.

it seems like sass only supports --color

All the more reason to add --color to svelte-check and then pass it down :D

[jasonlyu123]

Hmm. It works for me in an empty Sveltekit project. Maybe it has something to do with your preprocess setup. Can you provide a reproduction repository? Maybe the Sass compiler is executed in another child process or something. But if that is the case, we can't pass down the --color argument or the FORCE_COLOR variable since the child process isn't created by svelte-check but from your config.

[marekdedic]

Sorry for the slow response, but to summarize:

• I am not really that interested in fixing a one-off problem with sass-embedded, which I don't regularly use (I only used it to test your hypothesis)
• Independently of that, I think it would be great to support color output with whatever downstream tools are used. I'd be willing to try making a PR if you think that's something you want to support as well.
  Thanks!

[jasonlyu123]

I mentioned sass-embedded because it is the modern alternative to sass. So if sass-embedded could work then the problem is solved. The reason why I asked for a reproduction is that if the problem is your preprocess config runs sass in another thread/child process. Then there is nothing we can do. Supporting --color doesn't help because we can't control the child process to pass down the flag.

I think it's ok to have the --color flag since it is also supported by the coloring libary we used. Just wanted to make sure it can work for you. If you're interested in the PR you can test it yourself. Then I don't need the reproduction anymore. It should just be adding the argument to svelte-check's CLI options so that sade does errors with unknown options.