arktype•2mo ago

Easy way to validate enums

Brand new to Arktype(migrating over from Zod for perf reasons), and have a question about about handling enums. We have a fair number of enums that we use in our validation, example with Zod might be something like:

  period: z.nativeEnum(Period),

  period: z.nativeEnum(Period),

Seems like a way to do this in ArkType might be something like:

period: `"${Object.values(Period).join('"|"')}"`,

period: `"${Object.values(Period).join('"|"')}"`,

I tried to create a helper function so I don't have to do Object.values thing everywhere:

export const enumToArktype = (enumObj: Record<string, string>) => {
  return `"${Object.values(enumObj).join('"|"')}"`;
};

export const enumToArktype = (enumObj: Record<string, string>) => {
  return `"${Object.values(enumObj).join('"|"')}"`;
};

But Arktype doesn't seem to like the return type on this. Any ideas as to how to easily handle this use case?

15 Replies

ssalbdivad•2mo ago

Welcome! To get something like that to infer precisely you'd have to write type-level logic to make sure the return type is a narrowed string. Luckily, there is an easier way 😊 You can either use type.enumerated(... values) or an inline expression like punctuation: ["===", ".", "!"] https://arktype.io/docs/expressions#enumerated

ArkType Docs

Optimized runtime validation for TypeScript syntax

BenOP•2mo ago

Hmm, okay gonna need a little more hand holding here 😅 Specifically when it comes to the enums values specifically.

const enum Role = {
  user = "User"
  admin = "Admin"
  superAdmin = "Super Admin"
}

  type({
        id: "string",
        user: type.enumerated(...Object.values(Role))
      }),

const enum Role = {
  user = "User"
  admin = "Admin"
  superAdmin = "Super Admin"
}

  type({
        id: "string",
        user: type.enumerated(...Object.values(Role))
      }),

This works, but I'm guessing this isn't really what you meant since I'm back to using Object.values, and also I feel like an inline expression would work a lot better here, as compared to using the type in a type

ssalbdivad•2mo ago

ArkType doesn't have TS enums as a fist class concept because the ecosystem is trending toward --erasableSyntaxOnly with no compiled TS features like that. TBH I've never used them myself but essentially, just use whatever the easiest way is to get the narrowed list of values then pass that type.enumerated. Maybe Object.values is that in which case you pretty much have the optimal solution, but if you have many enums like that you may want a wrapper to make it more convenient. I know there have been a lot of utilities people have created over time, let me just double check what the most efficient thing to do would be for const enum

BenOP•2mo ago

Ya, we've moved away from them as well in favor of an object with as const, but we have like a dozen left in the codebase that we haven't gotten around to cleaning up. Really appreciate your help!

ssalbdivad•2mo ago

Are you sure it was a const enum? It looks like TS won't even compile that without a reference

BenOP•2mo ago

Ya seems like this working just fine for me

export enum Period {
  Week = "Week",
  PayPeriod = "Pay Period",
  SchedulePeriod = "Schedule Period",
}

export enum Period {
  Week = "Week",
  PayPeriod = "Pay Period",
  SchedulePeriod = "Schedule Period",
}

ssalbdivad•2mo ago

That isn't a const enum though hehe

BenOP•2mo ago

Oh woops My b Wow didn't even realize that was a thing

ssalbdivad•2mo ago

enum Role {
    user = "User",
    admin = "Admin",
    superAdmin = "Super Admin"
}

const valueOf = <obj extends object>(obj: obj): type<obj[keyof obj]> =>
    type.enumerated(...Object.values(obj)) as never

const t = type({
    id: "string",
    user: valueOf(Role)
})

enum Role {
    user = "User",
    admin = "Admin",
    superAdmin = "Super Admin"
}

const valueOf = <obj extends object>(obj: obj): type<obj[keyof obj]> =>
    type.enumerated(...Object.values(obj)) as never

const t = type({
    id: "string",
    user: valueOf(Role)
})

BenOP•2mo ago

Just went on autopilot lol

ssalbdivad•2mo ago

It's better you forget about it 😛

BenOP•2mo ago

Beautiful Thanks David!

ssalbdivad•2mo ago

So just reuse valueOf any time you want to reference an enum No problem!

BenOP•2mo ago

Excited to see my TS server go brrrr again soon 😉

ssalbdivad•2mo ago

Just wait until tomorrow, I hear there are some big announcements coming about that 🤫

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Easy way to validate enums

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