Proposed immutable.css functionality/API.

app.css

.u-i-will-be-opened-twice {
  color: yellow;
}

.u-actually-immutable-selector {
  content: 'I am not being reopened';
}

.awesome {
  font-variant: small-caps; /* Raises linting error (opened vendor.css selector) */
}

.u-i-will-be-opened-twice {
  background-color: red; /* Raises linting error (re-opened a util selector) */
}

linting.js

immutableCss.lint('vendor.css', 'app.css', { immutablePrefixes: ['.u-'] })

vendor.css

.awesome {
  color: green;
}

So if I understand correctly, immutablePrefixes would just scope the selectors that it's checking against with a prefix?

To me, altering any style from another file is bad practice. Also thinking about how this would work with Bootstrap.

I was thinking that immutablePrefixes would be in addition to ensuring style altering isn't occurring between files. I will update this gist to make it a bit more clear.

Okay, so now .awesome doesn't have a .u- prefix but would still raise an error. I'm thinking that there are particular prefixes, in addition to ensuring vendor CSS (bootstrap/basscss/etc), that we want to make sure aren't reopened.

Scaffolded out a project and added you as a collaborator, @jxnblk. If you want to move it under your name on Github let me know, I'm happy to transfer it over to you.

https://github.com/johnotander/immutable.css

Okay, I think this makes more sense now...

You're too fast, i'll move convo over to your repo