feature request: Check if a file is sorted already

[tylerbutler]

Thanks for the great library! I am using it to add some determinism to our tsconfig files in our monorepo. One thing that would be helpful for us is a faster way to check if a file is already sorted. We run checks in CI to verify that files are in the right state, and while we can just "always sort" it is a little slow compared to our other "checks."

I was thinking that it would be easiest to implement something like this in the core library. I am willing to open a PR if you have suggestions for where and how to implement this.

There should probably be a corresponding flag on the CLI package, too.

[duniul]

Hey!

I think an isSorted() export could make sense, with e.g. a --check flag on the CLI 👍 The simplest way I can think of would be to basically go through the parsed data like the sorter does, but only comparing fields with their next sibling. If we encounter a value that should be before it's sibling, we exit early.

Since the comments are irrelevant to the order of the fields, there is a possibility that it would be faster to just strip all comments and use a regular JSON.parse, but I'm not sure if that would be worth it.

If you're keen then a PR is of course super welcome! ⭐