Add support for non optional custom zod types

[pmsfc]

No description provided.

[samchungy]

This looks okay to me, I'll have another look when I have time to properly suss it out.

But would z.coerce.date() be more appropriate in your scenario?

[pmsfc]

This looks okay to me, I'll have another look when I have time to properly suss it out.

But would z.coerce.date() be more appropriate in your scenario?

I'm using LocalDate from the js-joda lib, just used Date as an example here.

[samchungy]

Hmmm I'm not entirely sure I like the approach of treating a custom as non optional by default given it can potentially return anything. Including undefined which in JavaScript world is also optional

[pmsfc]

Hmmm I'm not entirely sure I like the approach of treating a custom as non optional by default given it can potentially return anything. Including undefined which in JavaScript world is also optional

This solution won't do that because it's still calling zod's isOptional(), for example:

it('returns true for a custom undefined without a check', () => {
  const schema = z.custom<undefined>();
  const result = isOptionalSchema(schema, createOutputState());

  expect(result).toEqual({ optional: true });
});

it('returns true for a custom undefined with a check', () => {
  const schema = z.custom<undefined>((_: unknown) => false);
  const result = isOptionalSchema(schema, createOutputState());

  expect(result).toEqual({ optional: false });
});

For ex both of these will pass because zod will call the the safeParse(undefined).success when calling isOptional()

[samchungy]

You could also return something | undefined though in a custom.

[pmsfc]

You could also return something | undefined though in a custom.

From my understanding (I may be wrong) the type you pass to the custom won't matter. If you don't provide a check the schema.isOptional() will return true for custom types. But if you provide a check it won't be, its up to the check function to validate if it's optional by accepting undefined as a parsable input.

This is mainly because a z.custom without a check is a zod type of ZodAny but if it contains a check its a ZodEffects

For custom of string | undefined the following tests pass

  it('returns false for a custom string | undefined without a check', () => {
    const schema = z.custom<string | undefined>();
    const result = isOptionalSchema(schema, createOutputState());

    expect(result).toEqual({ optional: true });
  });

  it('returns false for a custom string | undefined with a check that returns false for undefined', () => {
    const schema = z.custom<string | undefined>(
      (toCheck: string | undefined) => toCheck !== undefined,
    );
    const result = isOptionalSchema(schema, createOutputState());

    expect(result).toEqual({ optional: false });
  });

  it('returns true for a custom string | undefined with a check that returns true for undefined', () => {
    const schema = z.custom<string | undefined>(
      (toCheck: string | undefined) => toCheck === undefined,
    );
    const result = isOptionalSchema(schema, createOutputState());

    expect(result).toEqual({ optional: true });
  });

[samchungy]

Ah awesome. TIL: https://github.com/colinhacks/zod/blob/1f4f0dacf313a2dba45563d78171e6f016096925/src/types.ts#L515

[samchungy]

Thank you for your work looking into this! I will take a final look tomorrow 🙂

[samchungy]

Thanks for this, I might end up re-writing all of the optional checking logic though but I'll keep your test cases