[Feature suggestion] A way to chain/pipe validations

Hello,

First of all, thank you for making and maintaining this awesome library.

I started using zod to validate forms on a frontend project, and found myself doing things like:

const FormData = z.object({
  age: z.string().transform((x, ctx) => {
    const value = parseInt(x)
    if (isNaN(value) || value < 0) {
      ctx.addIssue({code: z.ZodIssueCode.custom, message: 'should be a positif integer'})
      return z.NEVER
    }
    return value
  }),
  worked_days_in_month: z.string().transform((x, ctx) => {
    const value = parseInt(x)
    if (isNaN(value) || value < 0 || value > 31) {
      ctx.addIssue({code: z.ZodIssueCode.custom, message: 'should be an integer between 1 and 31'})
      return z.NEVER
    }
    return value
  }),
})

Since all values coming from the HTML inputs are strings, I have to validate them using z.string then use .transform to convert them to numbers and do additional validation.

I think it will be easier if after converting them to numbers, I could chain them to a z.number with some additional checks, something like:

const FormData = z.object({
  age: z.string().transform(x => parseInt(x)).chain(z.number().int().min(0)),
  worked_days_in_month: z.string().transform(x => parseInt(x)).chain(z.number().int().min(0).max(31)),
})

So my suggestion is to add a method .chain (or .pipe or other name …) that behaves as follows:

const a: ZodType // with types: _input = A and _output = B
const b: ZodType // with types: _input = B and _output = C

const c = a.chain(b) // gives a ZodType with _input = A and _output = C

Let me know if this is something you would be interested in adding to the library, I can try to make a PR for it if you agree.

[timm-stelzer-e-farm]

Looks like pipe is now built-in and should resolve this issue 😃

z.string()
  .transform(val => val.length)
  .pipe(z.number().min(5))

[timm-stelzer-e-farm]

tbh if you need to do that many nests you’re probably overcomplicating your Zod type. Just my 2c.

Fair enough, though this type of composition is fundamental in functional programming, and since zod was explicitly inspired by io-ts (a library where this kind of composition is built-in), it isn’t far-fetched to expect this kind of API.