Zod•12mo ago

janglad - Okay another question 😅 Why does t...

Okay another question 😅 Why does this return a ZodEffect with a possible unnkown?

export const defAString = z.preprocess(
  (val) => "this is def a string",
  z.string(),
);
// const defAString: z.ZodEffects<z.ZodString, string, unknown>

export const defAString = z.preprocess(
  (val) => "this is def a string",
  z.string(),
);
// const defAString: z.ZodEffects<z.ZodString, string, unknown>

18 Replies

Scott Trinh•12mo ago

I don't remember the signature there but I think that is the input type, which makes sense for preprocess

jangladOP•12mo ago

ooh huh yes you're right

jangladOP•12mo ago

this does indeed work as expected

export const stringOrEmptyToNull = z.preprocess(
  (val) => (val && typeof val === "string" ? val : null),
  z.string().nullable()
) 
// as z.ZodEffects<z.ZodNullable<z.ZodString>, string | null>;
// TODO: check above

const test = stringOrEmptyToNull.parse("test");
// const test: string | null

export const stringOrEmptyToNull = z.preprocess(
  (val) => (val && typeof val === "string" ? val : null),
  z.string().nullable()
) 
// as z.ZodEffects<z.ZodNullable<z.ZodString>, string | null>;
// TODO: check above

const test = stringOrEmptyToNull.parse("test");
// const test: string | null

altho somehow it does show up as unknown here, which is fixed by using that as that is commented right now

Scott Trinh•12mo ago

Yeah the output type is string so the type of the parsed value is string Every schema has an input and output type

jangladOP•12mo ago

oohhh yeah I am indeed using z.input hmm this is somewhat annoying lol cause IIRC I do need to do that as there are also transforms but then I'd need the output of that preprocess specifically 😄 altho actually no using z.output it still shows up as unknown there the schema setup is a bit complex so I'll need to do some digging as to where that's happening

Scott Trinh•12mo ago

What's the schema for street here?

jangladOP•12mo ago

that stringOrEmptyToNull but yes in the end it is indeed caused by using z.input which makes sense, output was just giving a different error which also makes sense but I guess I can just lie to TS here and use the as

Scott Trinh•12mo ago

Are you trying to construct a value and using the type as a type annotation without parsing it?

jangladOP•12mo ago

It's being used like this

 const emptyForm = generateEmptyForm(user);

  const defaultValues = create
    ? emptyForm
    :
transFormListing(props.defaultValues, user);

  const formSchema = create
    ? createListingInputSchema
    : updateListingInputSchema;

  type FormType = z.input<typeof formSchema>;

  const form = useForm<FormType>({
    defaultValues,
    resolver: zodResolver(formSchema),
    reValidateMode: "onSubmit",
  });

 const emptyForm = generateEmptyForm(user);

  const defaultValues = create
    ? emptyForm
    :
transFormListing(props.defaultValues, user);

  const formSchema = create
    ? createListingInputSchema
    : updateListingInputSchema;

  type FormType = z.input<typeof formSchema>;

  const form = useForm<FormType>({
    defaultValues,
    resolver: zodResolver(formSchema),
    reValidateMode: "onSubmit",
  });

Scott Trinh•12mo ago

Ahhh. Right. I wonder if instead of preprocess you should have a transform that checks for the empty string so that the input and output type is string | null still 🤔

jangladOP•12mo ago

that's not really ideal either. RHF sends an empty input as an empty string, if I then want to add on things like a min length I wouldn't be able to do say z.string().min(5).nullable().transform(emptyToNull) as when you pass it an empty string it complains about not being 5 long and while I can check for that in a refine, those only get triggered after all the other fields are valid so that's not great UX eitherr mind you I can't chain the min and such now either with the predefined variable but it is possible to do in a preprocess

Scott Trinh•12mo ago

z.union([
  z.literal("").transform(() => null),
  z.string().min(5).nullable(),
]);

z.union([
  z.literal("").transform(() => null),
  z.string().min(5).nullable(),
]);

You could do something like that maybe? Or:

z.string().transform((s) => s || null).pipe(
  z.string().min(5).nullable()
);

z.string().transform((s) => s || null).pipe(
  z.string().min(5).nullable()
);

jangladOP•12mo ago

second one would still have the issue of only validating after all the rest right but I had not thought of the first! that might actually be the most elegant solutioN!

Scott Trinh•12mo ago

I'm not sure what you mean here?

jangladOP•12mo ago

transforms and refines only run once other fields are valid right

Scott Trinh•12mo ago

It will be run in this case as long as it's a string maybe you're thinking about refines/transforms on an object (which requires that all of the properties pass their validations)?

jangladOP•12mo ago

yes I am indeed 😄

Scott Trinh•12mo ago

fwiw, I find the pipe implementation to be a bit more "accurate" to what you're trying to achieve in mapping an empty string to null and then adding addtional string constraints on any remaining strings, but both seem pretty readable. fwiw, i feel like these days pipe and coerce pretty much replace most use cases for preprocess.

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janglad - Okay another question 😅 Why does t...