Coerce z.string() into a z.number() or similar?

[KATT]

Is there a way to swap the primitive zod type from one to another?

Background

HTML <input />-fields are always string but in my backend, I want to coerce them into other types.

Example

// this work:
const strToNumber = z.string().transform(v => parseFloat(v))

// but I would also want to be able to use `z.number()`s props after transforming
// this does not work because `.min()` won't be a part of 
const strToNumber = z.string().transform(v => parseFloat(v)).min(0);

I would like to do something like:

const number = z.string()
  .transform(v => parseFloat(v))
  .coerce(z.number())
  .min(0)

Added complexity: .optional() and input number being ok

I'd ideally like something like this to work

const reqNumeric = z.numeric().min(0).optional()
const optionalNumeric = z.numeric().min(0).optional()

Where:

• optionalNumeric['_input'] = number | string | undefined
• optionalNumeric['_output'] = number | undefined
• reqNumeric['_input'] = number | string
• reqNumeric['_output'] = number

[KATT]

I am silly, there is .preprocess()!

[KATT]

Actually... that's not really sufficient, I want to define that the _input remains a string even if the _output gets coerced into a number.

import {z} from 'zod';

const castToNumber = z.preprocess((val) => Number(val), z.number());

// I would want this to be a `string`:
type TInput = typeof castToNumber['_input'];
//                                ^?


// And this to be a `number`:
type TOutput = typeof castToNumber['_output'];
//                                  ^?

https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbwF4F84DMoRHA5EiAE1wG4BYAKEoGMIA7AZ3moEMmAVCAOQFcQAjAKZQ4AXjhIAdGCiCZEaoIYMAFCoBuLADYBKMQD44vAcI3adAGgmS6fIVBU6d5KhQD0buAEk4Adwg8WoR+LHTwMAAWwAxwMBBwQnAscAAGTFDAdADmKQBclDAAnmCCcOxedGA88OJFJRDocKwc3HbCANq4APqZVTC4ALouHnCjY+MTk1PjAHoA-JSL7p4AgnTBkdGx8YnJKbYmUHkFxaXsAPLVfWKxpw1NbDCcxvadXQEwfYPDntN--5N5ksgA

[KATT]

I managed to write this that seem to do it https://www.typescriptlang.org/play?#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

But the .min(x), etc aren't available on ZodEffects :(

[KATT]

I also found zod-form-data but it doesn't seem to do the correct input type either:

https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgLwGYBM4F86qhEOAImQnQFpVoRz0BDGOogbgFgAoUSWRZHPAnADkpdEI4cAxhAB2AZ3hzJACwCmIOnAC8KDADoqUEABEGdABQIOcODLohVALl3o9MVQA8Y5gJQAaazg6AHMnFz0ZAFcHKGBJc2QI6IAjVShfPRBgGXMAJgBWH0y6D3N8gAYff0CAG2AAa1U5AAVgZGQ6ZzRXFVVJeuSIUur2LB82dg4lNQ0AbSEAfWywSJghAF15kNUNjgB6PZsj45ObAD0AfiA