Optional properties become required after merge

[chrchrd]

Hi,

I am testing different libraries that implement the Standard Schema interface to figure out which library to use in my app.

While testing version 11.0.0-alpha.4 of your library, I noticed a difference in output between your library and Zod and Valibot's library.

Using your library, I created a schema with optional properties:

export const SDocMeta = S.schema({
  _id: S.optional(S.string),
  _rev: S.optional(S.string),
  _deleted: S.optional(S.boolean),
})
export type SDocMeta = S.Output<typeof SDocMeta>

As expected, the properties of typeof SDocMeta are optional:

{
    _id?: string | undefined
    _rev?: string | undefined
    _deleted?: boolean | undefined
}

I then merge this schema with another:

export const Product = S.merge(SDocMeta, S.schema({
  code: S.min(S.string, 1, 'Product Code is required'),
  name: S.min(S.string, 1, 'Product Name is required'),
}))
export type Product = S.Output<typeof Product>

Unexpectedly, typeof Product becomes...

{
    _id: string | undefined
    _rev: string | undefined
    _deleted: boolean | undefined
    code: string
    name: string
}

...where the properties of SDocMeta are no longer optional.

This is different from Zod and Valibot's library. In those libraries, the optional properties stay optional after merging/extending a schema.

May you consider matching the behaviour of Zod and Valibot's library? Thanks!

[DZakh]

Thanks for letting me know. This is related to the types logic which should be improved.

[SX-3]

Nullable\nullish it also loses its type.