generic Omit function breaks type inferance

[JaeTLDR]

When using a function to omit shared keys among many schemas z.infer nolonger exports the underlying types correctly

import { z } from "zod";

const metaKeys = {
    _rid: z.string(),
    _self: z.string(),
    _etag: z.string(),
    _attachments: z.string(),
    _ts: z.string(),
};

function omitMetaKeys(schema: z.AnyZodObject): z.AnyZodObject {
    return schema.merge(z.object({...metaKeys})).omit(Object.keys(metaKeys).reduce((prev, curr) => { return { [curr]: true, ...prev } }, {}));
}

export const mySchema = z.object({
    id: z.string(),
});
export interface myType extends z.infer<typeof mySchema> {}
// works correctly complaining about the missing id property
const eg:myType ={}

export const myOmitSchema = omitMetaKeys(z.object({
    id: z.string(),
}));
export interface myOmitType extends z.infer<typeof myOmitSchema> {}
//does not complain, whihc is incorrect behaviour
const egOmit:myOmitType ={} 

if we use the same schema and remove the call to omitMetaKeys, we gain typing within vscode

[m10rten]

Hi,
My first thought is that it 'breaks' because you are returning z.AnyZodObject, and not a generic T extends AnyZodObject.

if you would change it into:

function omitMetaKeys<T extends z.AnyZodObject>(schema: T): Omit<z.infer<T>, 'key_a' | 'key_b'> {
    return schema.merge(z.object({...metaKeys})).omit(Object.keys(metaKeys).reduce((prev, curr) => { return { [curr]: true, ...prev } }, {}));
}

Then I believe it should work.

Try to extract the keys from your metadata, then you can use that in the Omit TS generic type.

[JaeTLDR]

Thanks this seems to be much closer, your code didn't seem to work for me, but the below did, however i am not sure how 'good' it is in comparison in terms of typescript correctness.

function omitMetaKeys<T extends z.AnyZodObject>(schema: T): T {
    return schema.merge(z.object({...metaKeys})).omit(Object.keys(metaKeys).reduce((prev, curr) => { return { [curr]: true, ...prev } }, {})) as T;
}

further suggestions are very welcome,

Thanks again