Nested discriminated unions

[gligoran]

I've got an object that has discriminated unions within discriminated unions:

[
  {
    "_id": "98439752-0cd4-406b-982f-1bbf1df5480d",
    "type": "data",
    "subtype": "subtype-1",
    "data": {
      "id": "a8d44d3f-c18a-4178-990c-f543ab8f3a8d",
      "url": "https://www.google.com",
      "title": {
        "en": "English title"
      }
    }
  },
  {
    "_id": "4f674fe7-368f-4b15-924b-7e61dd982961",
    "type": "data",
    "subtype": "subtype-2",
    "data": {
      "id": "160a6427-ec74-4488-bceb-8cebac86b55f",
      "path": "/",
      "description": "this is another subtype"
    }
  },
  {
    "_id": "aba34b25-8a33-4046-a62f-c5ff9a6befef",
    "type": "reference",
    "referent": {
      "id": "b940a1e8-3733-425f-b1ef-667c2ecdab04",
      "type": "document"
    }
  },
  {
    "_id": "aba34b25-8a33-4046-a62f-c5ff9a6befef",
    "type": "reference",
    "referent": {
      "id": "b940a1e8-3733-425f-b1ef-667c2ecdab04",
      "type": "file"
    }
  }
]

On the first level the type discriminator is the field type. For type: 'data', we can further discriminate the type by the field subtype.

When I try to do this with nested usage of discriminatedUnion like this:

import { z } from 'zod';

import data from './data.json';

const ReferenceSchema = z.object({
  _id: z.string(),
  type: z.literal('reference'),
  referent: z.object({
    id: z.string(),
    type: z.enum(['document', 'file']),
  }),
});

const Subtype1Schema = z.object({
  _id: z.string(),
  type: z.literal('data'),
  subtype: z.literal('subtype-1'),
  data: z.object({
    id: z.string(),
    url: z.string().url(),
    title: z.object({
      en: z.string(),
    }),
  }),
});

const Subtype2Schema = z.object({
  _id: z.string(),
  type: z.literal('data'),
  subtype: z.literal('subtype-2'),
  data: z.object({
    id: z.string(),
    path: z.string(),
    description: z.string(),
  }),
});

const DataSchemma = z.discriminatedUnion('subtype', [
  Subtype1Schema,
  Subtype2Schema,
]);

export const Schema = z.array(
  z.discriminatedUnion('type', [ReferenceSchema, DataSchemma])
);

const rc = Schema.parse(data);

I get an error saying:

Error: The discriminator value could not be extracted from all the provided schemas

How can I achieve that once my code checks if type === 'data' TypeScript knows that now, there's a field subtype and an object called data?

You can play with this example here: https://stackblitz.com/edit/typescript-piewve?devToolsHeight=33&file=index.ts

[maxArturo]

There's an open PR for this @gligoran https://github.com/colinhacks/zod/pull/1589. The functionality will hopefully also be upgraded with intersections and other Zod types that make sense.

[stale[bot]]

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