Zod 3 `transform` breaking change

In version 2 we utilised zod.transform method to transform an object into an array, and validated each array item. Using zod.array directly resulted in parse error ‘Expected an array, received object’.

Background: in Ember Data hasMany relations are essentially objects, but semantically they represent collections: they treat themselves as array-like structures with implementation of map, filter and others, and capable of returning a true array via toArray method.

Version 2 code:

interface SyncHasMany<T> {
  // ...
  toArray(): T[];
}

function hasMany<T extends zod.ZodTypeAny>(itemSchema: T): zod.ZodTransformer<zod.ZodUnknown, zod.ZodArray<T>> {
  return zod.unknown().transform(
    zod.array(itemSchema),
    // In case it is hasMany we should convert it to plain Array so Zod can digest it.
    rel => Array.isArray(rel) ? rel as zod.TypeOf<T>[] : (rel as SyncHasMany<zod.TypeOf<T>>).toArray(),
  );
}

But in ver. 3 this approach is no longer available. The question is how can I achieve the same result now? I want zod to validate a hasMany relation using zod.array(itemSchema) schema as if the content of this relation was a plain array.

[azhiv]

@colinhacks zod.preprocess works great, thank you very much!

[colinhacks]

Excellent!