Warn if rfs is imported more than once

[MartijnCuppens]

Throw a warning if RFS is imported more than once.

[lucagouty]

hello @MartijnCuppens 😃

I'm a bit confused about this warning, as it's imported from bootstrap/scss/_mixins.scss :
https://github.com/twbs/bootstrap/blob/1ded0d6a4eefb7daca62c44e4e735aec200f0b6f/scss/_mixins.scss#L5-L6

Before that, bootstrap never warned about including ~boostrap/scss/mixins multiple times, but now it does.

If everyone think it's really bad to import mixins multiple times, then I think we should do it in bootstrap/scss/mixins but not only for rfs, what do you think ?

But to be honest, I'm not sure it's necessary, especially for mixins. If we want to add that kind of warning, we should do it in places that "generate" css (to avoid having same rules defined multiple times), it makes more sense. But for now bootstrap don't warn for this, so having it for some mixins seems weird IMO.

PS : Anyway, thank you because it made me realise I was badly importing things on my apps, and now I'm not having the warning anymore, so it's all good for me 😉

[MartijnCuppens]

Hi @lucagouty,

That might be a good idea, can you make an issue on the Bootstrap repo about this, since that is a separate project and we'll need to have a look where we can add that.