Coerce values of certain types while allowing values of other types

[allen-liaoo]

Hi,
I'm new to zod. I want to be able to coerce string to number, but I want to allow the value that is null to remain null. I'm not sure how to specifically allow null to pass through uncoerced because coerce would raise an error.

Without handling null values:

z.string().or(z.number()).pipe(z.coerce.number())

Option 1:

z.union([
    z.string(), 
    z.number(), 
    z.null()
]).pipe(z.coerce.number())

Option 1 doesn't work because Number constructor will be called with either null, which is not what I intended. I want null to remain null.

Option 2:

z.union([
    z.string().or(z.number()).pipe(z.coerce.number()), 
    z.null()
])

Option 2 doesn't work because if null is encountered, z.coerce.number() raises an error.

Any help would be appreciated!

[BrendanC23]

You can write your own transform function:

const schema = z.object({
    field: z
        .string()
        .or(z.number())
        .nullable()
        .transform((data, ctx) => {
            if (data === null || typeof data === "number") return data;

            const asNumber = Number(data);

            if (isNaN(asNumber)) {
                ctx.addIssue({
                    code: z.ZodIssueCode.custom,
                    message: `The value for "data" is not valid.`,
                });

                return z.NEVER;
            }

            return asNumber;
        }),
});

type schemaInput = z.input<typeof schema>; // { field: string | number | null }
type schemaOutput = z.output<typeof schema>; // { field: number | null }

[allen-liaoo]

I see, thank you!
Do you know what the difference is between a ZodEffect and a ZodSchema? like what functions are defined for each? The docs weren't super clear about this.