discriminatedUnion errors with z.object().transform()

[caillou]

Playground

import { z } from 'zod';

const ZodFoo = z.object({type: z.literal('foo'), foo: z.string()})
  .transform(({type, foo}) => ({type, value: foo}));
const ZodBar = z.object({type: z.literal('bar'), bar: z.string()})
  .transform(({type, bar}) => ({type, value: bar}));

const ZodBaz = z.discriminatedUnion('type', [ZodFoo, ZodBar]);

I am not sure if this is even possible.

If not, is there a recommended workaround?

[azhiv]

What exactly are you trying to achieve? Discriminating types usually result in several different types. In your case they are both of the same one:

{
  type: 'foo' | 'bar',
  value: string;
}

If the main purpose of the transformations are further manipulations/refinements, will this be suitable for your needs:

const ZodFoo = zod.object({type: zod.literal('foo'), foo: zod.string()});
const ZodBar = zod.object({type: zod.literal('bar'), bar: zod.string()});
const ZodBaz = zod.discriminatedUnion('type', [ZodFoo, ZodBar])
  .transform(obj => ({
      type: obj.type,
      value: obj.type === 'foo' ? obj.foo : obj.bar,
  }));

?

[caillou]

@azhiv thanks for your feedback. I tried to reduce the example to a minimum for the sake of simplicity. Yet I did not succeed ;)

Let me try again:

Playground

const ZodFoo = z.object({type: z.literal('foo'), foo: z.string()});
const ZodBar = z.object({type: z.literal('bar'), bar: z.string().optional(), fallback: z.string()})
  .transform(({type, bar, fallback}) => ({type, bar: bar || fallback}));
const ZodBaz = z.discriminatedUnion('type', [ZodFoo, ZodBar]);

[azhiv]

Ok, I couldn't find a way to combine transform with discriminatedUnion, maybe you're right and this is simply not supported.
The approach below is not that elegant and may be not something you were looking for, but If you possess control over the input types, I'd suggest defining a type with all transformations applied, so that the validation schema could be simplified. In the example above, you could define a separate getter like deducedBar returning bar || fallback, and then define a schema for this object, providing it to discriminatedUnion. Hope that helps!

[roblabat]

Duplicate of #1171 with the openned PR #1290 fixing this issue and waiting for feed back or merge.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.