Tagging of properties, retrievable at runtime

[nidomiro]

I'm currently using zod, but like the idea of using types only for my project.
So far every thing would work, but I would need to be able to mark properties, so I can identify them at runtime.
My specific usecase is that I have a schema for a db-event in event-sourcing, but want to mark specific fields as PII (Personal Identifiable Data) to be able to store these fields in another store and only the reference to them to the event-stream.

For that to be possible I need the information at runtime.
I currently see two possible solutions:

1. While checking, alter the checked object and annotate the actual properties.
2. Add an additional function to typia that returns the paths of tags.

While 1 would be optimal in usage, I doubt that this is a good idea, since a is check should not alter anything and be pure.
The second approach is a bit more work, and has the challenge of union and array types, but would be pure and does not alter anything.

A possible api:

import typia, { tags } from 'typia';
 
interface IMember {
  id: string & tags.Format<'uuid'>;
  name: string 
    & tags.runtimeTag<'PII'>
    & tags.MinLength<1>
}

const piiTagPaths = typia.getRuntimeTags<'PII'>()

What is your opinion on that?