hoshi Comments - Answer Overflow

hoshi

•Created by hoshi on 8/3/2024 in #questions

How to test nextjs app against dockerized postgres container (Vercel)

Also open to using Github actions. Something like this seems promising https://gist.github.com/2color/537f8ef13ecec80059abb007839a6878

4 replies

TTCTheo's Typesafe Cult

•Created by hoshi on 9/30/2022 in #questions

Typescript Function to make specific nested keys non nullable?

Wow thanks, really appreciate breaking it down for me like that. I think I understand it a lot more now. I was not expecting never to extend everything else but now that I think about it, it makes sense given that never is an empty set. So of course an empty set is a subset of all other sets. I actually wanted GetUniquePaths to filter out the most "shallow" path and retain the deeper paths. So I wanted this output:

type t1 = GetUniquePaths<"a.c" | "a" | "c"> // => "a.c" | "c"

type t1 = GetUniquePaths<"a.c" | "a" | "c"> // => "a.c" | "c"

Thanks to your explanation, I ended up implementing it like this:

type IsSubPath<Paths extends string, P extends string> = Paths extends unknown
  ? Paths extends `${P}.${string}`
    ? true
    : false
  : never

type GetUniquePaths<T extends string, P extends string = T> = P extends P
  ? IsSubPath<T, P> extends false
    ? P
    : never
  : never


type t1 = GetUniquePaths<"a" | "a.b" | "c" | "c.a" | "a.b.c" | "c.d"> // "c.a" | "a.b.c" | "c.d"

type IsSubPath<Paths extends string, P extends string> = Paths extends unknown
  ? Paths extends `${P}.${string}`
    ? true
    : false
  : never

type GetUniquePaths<T extends string, P extends string = T> = P extends P
  ? IsSubPath<T, P> extends false
    ? P
    : never
  : never


type t1 = GetUniquePaths<"a" | "a.b" | "c" | "c.a" | "a.b.c" | "c.d"> // "c.a" | "a.b.c" | "c.d"

13 replies

TTCTheo's Typesafe Cult

•Created by hoshi on 9/30/2022 in #questions

Typescript Function to make specific nested keys non nullable?

Trying to come up with a typescript function to filter out "subpaths" now. It seems like it should be easy but I'm getting stuck with the peculiarities with how unions are distributed in a condition.

type FilterForA<T extends string, P = T> = P extends P
  ? P extends "a" ? P : never : never

type FilterForAV2<T extends string, P = T> = P extends P
  ? Exclude<P, "c"> extends "a" ? P : never : never

type t1 = FilterForA<"a.c" | "a" | "c">     // gives "a"
type t2 = FilterForAV2<"a.c" | "a" | "c">   // gives "c" | "a" for some reason

type FilterForA<T extends string, P = T> = P extends P
  ? P extends "a" ? P : never : never

type FilterForAV2<T extends string, P = T> = P extends P
  ? Exclude<P, "c"> extends "a" ? P : never : never

type t1 = FilterForA<"a.c" | "a" | "c">     // gives "a"
type t2 = FilterForAV2<"a.c" | "a" | "c">   // gives "c" | "a" for some reason

13 replies

TTCTheo's Typesafe Cult

•Created by hoshi on 9/30/2022 in #questions

Typescript Function to make specific nested keys non nullable?

13 replies

TTCTheo's Typesafe Cult

•Created by hoshi on 9/30/2022 in #questions

Typescript Function to make specific nested keys non nullable?

13 replies

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