Proposal: `AppendKeys` `PrependKeys`

[pkuczynski]

Would allow to easily modify all the keys of an interface by appending or prepending the given string:

interface Operations {
  get: () => any
  update: () => any
}

type CustomOperations = AppendKeys<Operations, 'Something'>

would produce a type equivalent to:

interface CustomOperations {
  getSomething: Operations['get']
  updateSomething: Operations['update']
}

My use case is that I have a generator function, which produces an object of methods and I would like to re-export the same interface with some custom names:

const operations = (id: number): Operations => {
  get: () => { ... }
  update: () => { ... }
}

const ship = (id: number): Operations<'Ship>> => {
  const { get, update } = operations(id)
  
  return {
     getShip: get
     updateShip: update
  }
}

I am willing to create PR once this is accepted...

[sindresorhus]

I cannot say I ever needed this, and I kinda feel like there must be a better way of solving this. For example, I don't see why the method names should change. It's already a unique instance. ship.getShip() feels moot. ship.get() would be clear enough.

I'll leave this open for others to comment.

Also, this should be AppendToKeys, not AppendKeys.

[pkuczynski]

Yeah, didn't like the naming myself but could not figure something else...

As for the usage, in my case, I have a core useApi hook that exports generic get, create, etc. And then I have useX and useY hooks, which use the useApi hook, initialize it with some values, and re-export those methods as getX, getY etc, so I can use them independently on one page. I could of course export with [] instead of {}, so giving custom names on the spread would be easily possible, yet I wanted the flexibility to easier cherry pick from {}.

Regardless of my exact usage, the implementation of that type would be fairly easy:

type AppendToKeys<Name extends string, T> = { [key in keyof T as ${string & key}${Name}]: T[key] }

Its just a proposal, so if anybody finds it useful, I can fire up PR...