optional handling in object

[jordan-boyer]

given the following snippet

const person = object({
    name: string().or(optional()),
    age: number(),
  });

type Person = Infer<typeof person>;

we have the resulting person type

type Person = {
    name: string | undefined;
    age: number;
}

where we could have

type Person = {
    name?: string | undefined;
    age: number;
}

what do you think ?

[adversinc]

I second that. Infer<> does not generate the optional parameters so the following code results an error:

const person = object({
    name: string().or(optional()),
    age: number().or(optional()),
  });

type Person = Infer<typeof person>;

function updatePerson(personData: Person = {}) { ... }

It would be great to get it fixed.

[thoughtspile]

Ouch, looks like superstruct typetest suite has failed me:

banditypes/tests/typings/optional.ts

Lines 6 to 12 in 0b992f7

	test<{
	a?: number | undefined
	b: string
	}>(object({
	a: number().or(optional()),
	b: string(),
	}))

The inferred type is assignable to the target one, but they're not equal.

[jordan-boyer]

If you want a better test you can add this "exactOptionalPropertyTypes": true and write the test like this:

test<{
  a?: number
  b: string
}>(object({
  a: number().or(optional()),
  b: string(),
}))

which typescript complain without a proper fix for the optional on object

[thoughtspile]

Fixed in 0.2.3

I also updated the typetest suite for strict checks, and opened an issue in superstruct in case they'd like to avoid problems like these.