Default value for an invalid field of object

[Senbonzakura1234]

In zod there is a pattern to set initial value in case undefined and default value on error
Example:

export const searchQueryValidator = z.object({
    sortBy: z.enum(['index', 'name', 'level', 'price']).nullish().catch(null).default(null),
    direction: z.enum(['asc', 'desc']).nullish().catch(null).default(null),
});

If either sortBy or direction was invalid or undefined, they will be set to null and not throw error on parse execution.
This behavior really useful to parse URL queries since it prevents the URL queries getting crowded by empty field when value was undefined which makes the URL looks ugly.

Is there a way to achieve this in arktype?

[ssalbdivad]

Unfortunately we have "catch morphs" planned but not available yet (still need to add a description😅):

#611

For right now the best workaround would be to use a broad input type like unknown, then call the simple validator from a morph to check whether the value is allowed:

const validSortBy = type(
    "'index' | 'name' | 'level' | 'price' | null | undefined"
)

const validDirection = type("'asc' | 'desc' | null | undefined")

export const myType = type({
    sortBy: morph("unknown", (value) =>
        validSortBy.allows(value) ? value : null
    ),
    orderBy: morph("unknown", (value) =>
        validDirection.allows(value) ? value : null
    )
})

You can mess around with the approach on StackBlitz here:

https://stackblitz.com/edit/mrvfrm-ytjzwk?file=type.ts

Note that the upcoming #763 would be separate, since for now it does not apply if the key is present but has a value of undefined, like TypeScript's extractOptionalPropertyTypes (I'm considering changing this though as I could imagine it being a point of confusion). If you need to set a key that is not present in an object, you currently have to "up a level" and morph the object it belongs to:

const PersonArktype = morph(
  {
    name: "string"
  },
  (person) => ({ ...person, lengthOfName: person.name.length })
);

[Senbonzakura1234]

@ssalbdivad tks, i think i will wait for the next update though

[Senbonzakura1234]

@ssalbdivad btw, when this feature is ready, please inform me here in this discussion. Tks

[airtonix]

@Senbonzakura1234 were you ever informed that this feature was deployed?

[airtonix]

It looks like you can do this with

const page = type("number>1").default(1)

or am I missing something?

or is this the right way?

export const ThemeSchema = type({ 
    'name': '"light" | "dark" | "system" = "system"' 
});

btw @ssalbdivad I couldn't find this in the docs, does that mean this is not the right way to achieve this?

[ssalbdivad]

The docs for default values are here:

https://arktype.io/docs/objects#properties-defaultable

But that's not the same as a fallback for an invalid value which hasn't been implemented yet.