Support config the behaviours for the option type

[rainbowatcher]

Hi, Thanks for the amazing project, I'm building a project using Axum and Specta, I've created a request body with optional fields, However, Specta is converting id: Option<i32> to id: number | null, but I'm expecting id?: number. Could you please add support for configuring this behavior in export::ts_with_cfg()?

Or do you have a better idea?

[oscartbeaumont]

#[serde(optional)] is the best we have right now. I think it exports as id?: number | null.

This is way more of Serde thing than a Specta thing. We are required to copy what is decides to serialize/deserialize the value as although here is some possible improvements around types that implement one and not the other trait.

[rainbowatcher]

Thank you for your reply.

I've used #[specta(optional)], which is good, but sometimes it's still not perfect. I get confused when I define a function and call it like this:

type User = { name?: string | null }
// ^ this is specta output type

const user = { name: "tony" }

function foo(a?: string) {
	console.log(a)
}

foo(user.name) // this line will throw a error: Type 'null' is not assignable to type 'string | undefined'

it must be declare like follow to avoid that error

function foo(a?: string | null) {
	console.log(a)
}

When I call a third-party function within this function, I encounter exceptions again.
as developers often eschew the use of null,
So the function can only be as follows.

function foo(a?: any) {
	thirdPartyFn(a)
}

I have read the issue from rspc specta-rs/rspc#100, And I think the TypeScript modules are specifically designed for generating TypeScript types, so generating more natural TypeScript types should be considered.

[oscartbeaumont]

You can use ?? undefined instead, using any is very rarely a good solution (playground).

but yeah as discussed in that other issue we will probaly split the handling of serialization and deserialization so we can potentially automatically apply #[specta(optional)] when using using#[serde(skip_serializing_if = "")] or similar although many questions still remain about how we are going to actually make that work.