Nested z.discriminatedUnion

[antoniogiroz]

Hello!

I'm trying to pass from this type:

type Pipe = {
  name: string;
  executionMode: 'Manual' | 'Periodical';
  executionFrequencyMode?: 'Simple' | 'Advanced';
  frequencyValue?: string;
};

To that:

export type PipeModeManual = {
  name: string;
  executionMode: 'Manual';
};

export type PipeModePeriodicalSimple = {
  name: string;
  executionMode: 'Periodical';
  executionFrequencyMode: 'Simple';
  frequencyValue: number;
  frequencyUnit: number;
};

export type PipeModePeriodicalAdvanced = {
  name: string;
  executionMode: 'Periodical';
  executionFrequencyMode: 'Advanced';
  frequencyValue: string;
};

Where executionMode and executionFrequencyMode should be discriminated unions.

I'm trying something like the following, but I get typescript errors:

const PipelineExecutionMode = z.union([z.literal('Manual'), z.literal('Periodical')]);
const PipelineFrequencyUnit = z.union([z.literal('Minute'), z.literal('Hour')]);
const PipelineExecutionFrequencyMode = z.union([z.literal('Simple'), z.literal('Advanced')]);

const SimplePipelineSchema = z.object({
  executionFrequencyMode: z.literal('Simple'),
  frequencyValue: z.number(),
  frequencyUnit: PipelineFrequencyUnit,
});

const AdvancedPipelineSchema = z.object({
  executionFrequencyMode: z.literal('Advanced'),
  frequencyValue: z.number(),
});

const BasePipelineSchema = z.object({
  name: z.string(),
  executionMode: PipelineExecutionMode,
});

const PipelineSchema = z.discriminatedUnion('executionMode', [
  BasePipelineSchema.extend({
    executionMode: z.literal('Manual'),
  }),
  BasePipelineSchema.extend({
    executionMode: z.literal('Periodical'),
    executionFrequencyMode: PipelineExecutionFrequencyMode,
    // How add another discriminator here base on executionFrequencyMode?
  }),
]);

Is it possible to add more nested discriminated unions?

Thanks a lot!

[antoniogiroz]

This works:

const PipelineSchema = z.discriminatedUnion('executionMode', [
  BasePipelineSchema.extend({
    executionMode: z.literal('Manual'),
  }),
  BasePipelineSchema.extend({
    executionMode: z.literal('Periodical'),
    executionFrequencyMode: z.literal('Simple'),
    frequencyValue: z.number(),
    frequencyUnit: PipelineFrequencyUnit,
  }),
  BasePipelineSchema.extend({
    executionMode: z.literal('Periodical'),
    executionFrequencyMode: z.literal('Advanced'),
    frequencyValue: z.string(),
  }),
]);

But I'd like to know if there is a better way.

[yss14]

@antoniogiroz Tried out your proposed workaround, but I receive the following error: Error: Discriminator property executionMode has duplicate value Periodical. How can this work on your side? Do you use an older version of zod?

[antoniogiroz]

Sorry @yss14, but finally the entity changed and I declared the interfaces with Typescript instead of generated by Zod, so I don't remember how the above code worked.

[greym0uth]

For future readers:

The way I got around was just to place the secondary (inner) discriminated union into it's own object so there isn't a duplicate:

const PipelineSchema = z.discriminatedUnion('executionMode', [
  BasePipelineSchema.extend({
    executionMode: z.literal('Manual'),
  }),
  BasePipelineSchema.extend({
    executionMode: z.literal('Periodical'),
    frequency: z.discriminatedUnion('executionFrequencyMode', [
      z.object({
        executionFrequencyMode: z.literal('Simple'),
        frequencyValue: z.number(),
        frequencyUnit: PipelineFrequencyUnit,
      }),
      z.object({
        executionFrequencyMode: z.literal('Advanced'),
        frequencyValue: z.number(),
      }),
    ])
  }),
]);

Now there is no longer a duplicate executionMode. If you must have them both at the same level in the object then I have no clue and bashed my head against a wall for several hours trying to figure out, but I don't think I can come up with a scenario where you can't do the above since you can always just remap afterwards if absolutely necessary.