I have a field where I want the value to either be optional OR have the field have a minimum length of 4
.
I've tried the following:
export const SocialsSchema = z.object({
myField: z.optional(z.string().min(4, "Please enter a valid value")),
});
This passes if I used a value like: "good"
, but if I've got an empty value then it fails.
How do I correctly implement a constraint using zod schemas to make an optional value with a minimum constraint if the value is not empty?
Is it possible to do this without using regex or a regex solution the only way?
In your case, you consider ""
to be the same as undefined
(ie: when the string is empty, it's like there's no string at all).
It's implementable in Zod this way:
import { z } from "zod";
import { strict as assert } from "node:assert";
// `myString` is a string that can be either optional (undefined or missing),
// empty, or min 4
const myString = z
.union([z.string().length(0), z.string().min(4)])
.optional()
.transform(e => e === "" ? undefined : e);
const schema = z.object({ test: myString });
assert( schema.parse({}).test === undefined ); // missing string
assert( schema.parse({ test: undefined }).test === undefined ); // string is undefined
assert( schema.parse({ test: "" }).test === undefined ); // string is empty
assert( schema.parse({ test: "1234" }).test === "1234" ); // string is min 4
// these successfully fail
assert( schema.safeParse({ test: "123" }).success !== true );
assert( schema.safeParse({ test: 3.14 }).success !== true );
Here you are:
import { z } from "zod";
export const SocialsSchema = z.object({
myField: z.string().min(4, "Please enter a valid value").optional()
});
// ok
console.log(SocialsSchema.parse({ myField: undefined }));
// ok
console.log(SocialsSchema.parse({ myField: "1234" }));
// ok
console.log(SocialsSchema.parse({ myField: "" }));
// throws min error
console.log(SocialsSchema.parse({ myField: "123" }));
Based on this Github issue and it's answer
Use the or
-option in-combined with optional & literal, like this.
export const SocialsSchema = z.object({
myField: z.string().min(4, "Please enter a valid value"))
.optional()
.or(z.literal('')),
});
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