Function which receives a arktype's 'type'

I'm trying to do something like this:

  async rateLimitedCallApi<T>(url: string, schema: Type<T>): Promise<T> {
    await this.rate_limiter.acquire();
    
    const response = await fetch(url, this.request_data);
    if (!response.ok) {
      throw Error(`Invalid request: ${response}`)
    }
    
    const parsedResponse = schema(await response.json());

  async rateLimitedCallApi<T>(url: string, schema: Type<T>): Promise<T> {
    await this.rate_limiter.acquire();
    
    const response = await fetch(url, this.request_data);
    if (!response.ok) {
      throw Error(`Invalid request: ${response}`)
    }
    
    const parsedResponse = schema(await response.json());

But the parsedResponse isn't of type T, so how do I make this function accept as schema anything created using type({...})

6 Replies

Stuart B•2mo ago

try:

  async rateLimitedCallApi<T extends Type>(url: string, schema: T)

  async rateLimitedCallApi<T extends Type>(url: string, schema: T)

ssalbdivad•2mo ago

What do you mean that it's not of type T? T is not constrained here. Are you just not wanting to cast the return? If that's the case it is likely a limitation of TS. It falls apart very quickly trying to do anything with generic types in a function. See my recommendation here: https://discord.com/channels/957797212103016458/1289555141355241573/1289572327511687208 This will generally work in the default scope, but use type.Any if you want it to accept all type instances

Stuart B•2mo ago

Good to know!

CobainOP•2mo ago

  async rateLimitedCallApi<T>(url: string, schema: Type<T>): Promise<T> {
    await this.rate_limiter.acquire();

    const response = await fetch(url, this.request_data);
    if (!response.ok) {
      throw Error(`Invalid request: ${response}`);
    }

    const json = await response.json();
    const parsedResponse = schema(json);

    if (parsedResponse instanceof type.errors) throw parsedResponse;

    return parsedResponse as T;
  }

  async rateLimitedCallApi<T>(url: string, schema: Type<T>): Promise<T> {
    await this.rate_limiter.acquire();

    const response = await fetch(url, this.request_data);
    if (!response.ok) {
      throw Error(`Invalid request: ${response}`);
    }

    const json = await response.json();
    const parsedResponse = schema(json);

    if (parsedResponse instanceof type.errors) throw parsedResponse;

    return parsedResponse as T;
  }

So casting here is ok if I don't cast it, the parsedResponse has this type: finalizeDistillation<T, _distill<T, { endpoint: "out"; }>>

ssalbdivad•2mo ago

Yeah like I said it's just a TS limitation it can't actually evaluate expressions on generic parameters You can see how there's really no unique arktype logic here so that's not something I control Because if you use the schema on its own it is inferred correctly

CobainOP•2mo ago

Yeah typescript with generic types in functions has never worked well I understand, thanks!

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Function which receives a arktype's 'type'