Infer types

Another cool feature that my schemas allow you to do is to infer the input and output type. This makes your work even easier, because you don't have to create the type definition additionally.

Infer input types

The input type of a schema corresponds to the TypeScript type that the incoming data of a schema must match to be valid. To extract this type you use the utility type InferInput.

You are probably interested in input type only in special cases. I recommend you to use the output type in most cases.

import * as v from 'valibot';

const LoginSchema = v.object({
  email: v.string(),
  password: v.string(),
});

type LoginInput = v.InferInput<typeof LoginSchema>; // { email: string; password: string }

Infer output types

The output type differs from the input type only if you use optional, nullable or nullish with a default value or brand, readonly or transform to transform the input or data type of a schema after validation. The output type corresponds to the output of parse and safeParse. To infer it, you use the utility type InferOutput.

import * as v from 'valibot';
import { hashPassword } from '~/utils';

const LoginSchema = v.pipe(
  v.object({
    email: v.string(),
    password: v.pipe(v.string(), v.transform(hashPassword)),
  }),
  v.transform((input) => {
    return {
      ...input,
      timestamp: new Date().toISOString(),
    };
  })
);

type LoginOutput = v.InferOutput<typeof LoginSchema>; // { email: string; password: string; timestamp: string }

Infer issue types

You can also infer the possible issues of a schema. This can be useful if you want to handle the issues in a particular way. To extract this information from a schema you use the utility type InferIssue.

import * as v from 'valibot';

const LoginSchema = v.object({
  email: v.pipe(v.string(), v.email()),
  password: v.pipe(v.string(), v.minLength(8)),
});

type Issue = v.InferIssue<typeof LoginSchema>; // v.ObjectIssue | v.StringIssue | v.EmailIssue<string> | v.MinLengthIssue<string, 8>

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