Is there any way to know the given object is Valibot schema?

[chrg1001]

Is there any way to know the given object is Valibot schema?

I want to do something like this

const isValibotSchema = (input: unknown): input is ValibotSchema => {
  // like `input instanceof $ZodType`
  return ...
}

[dosubot[bot]]

Hi @chrg1001! I'm Dosu and I’m helping the valibot team.

Valibot doesn't have a built-in instanceof or isSchema method for runtime schema detection, but you can reliably identify a Valibot schema by checking for the presence of the internal symbol Symbol.for('ValiType') on the object. This is the canonical marker used by Valibot for schema objects¹.

Here's a TypeScript-compatible type guard you can use:

import type { GenericSchema } from 'valibot';

export function isValibotSchema(input: unknown): input is GenericSchema<unknown> {
  return (
    typeof input === 'object' &&
    input !== null &&
    Symbol.for('ValiType') in input
  );
}

This approach works for all standard Valibot schemas. If you use custom schemas or deeply composed schemas, make sure they preserve this symbol. For TypeScript type safety, you can use GenericSchema as the schema type².

To reply, just mention @dosu.

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Footnotes

1. Valibot schemas use Symbol.for('ValiType') for identification ↩

2. GenericSchema is recommended for TS safety ↩