io-ts-reporters

Error reporters for io-ts.

Currently this package only includes one reporter. The output is an array of strings in the format of:

Expecting ${expectedType} at ${path} but instead got: ${expectedType}

And for union types:

Expecting one of:
    ${unionType1}
    ${unionType2}
    ${...}
    ${unionTypeN}
at ${path} but instead got: ${actualValue}

Example

import * as t from 'io-ts';
import reporter from 'io-ts-reporters';

const User = t.interface({ name: t.string });

// When decoding fails, the errors are reported
reporter.report(User.decode({ nam: 'Jane' }));
//=> ['Expecting string at name but instead got: undefined']

// Nothing gets reported on success
reporter.report(User.decode({ name: 'Jane' }));
//=> []

To only format the validation errors in case the validation failed (ie. mapLeft) use formatValidationErrors instead.

import * as t from 'io-ts';
import { formatValidationErrors } from 'io-ts-reporters';
import * as E from 'fp-ts/lib/Either';
import { pipe } from 'fp-ts/lib/pipeable';

const User = t.interface({ name: t.string });

const result = User.decode({ nam: 'Jane' }); // Either<t.Errors, User>

E.mapLeft(formatValidationErrors)(result); // Either<string[], User>

For more examples see the tests.

Credits

This library was created by OliverJAsh.