io-ts-extra/dist/narrow.d.ts

Adds pattern matching, optional properties, and several other helpers and types, to io-ts.

import { TypeOf, RefinementC, Context, Any } from 'io-ts';
/**
 * Like io-ts's refinement type but:
 * 1. Not deprecated (see https://github.com/gcanti/io-ts/issues/373)
 * 2. Passes in `Context` to the predicate argument, so you can check parent key names etc.
 * 3. Optionally allows returning another io-ts codec instead of a boolean for better error messages.
 *
 * @example
 * const CloudResources = narrow(
 *   t.type({
 *     database: t.type({username: t.string, password: t.string}),
 *     service: t.type({dbConnectionString: t.string}),
 *   }),
 *   ({database}) => t.type({
 *     service: t.type({dbConnectionString: t.literal(`${database.username}:${database.password}`)}),
 *   })
 * )
 *
 * const valid = CloudResources.decode({
 *   database: {username: 'user', password: 'pass'},
 *   service: {dbConnectionString: 'user:pass'},
 * })
 * // returns a `Right`
 *
 * const invalid = CloudResources.decode({
 *   database: {username: 'user', password: 'pass'},
 *   service: {dbConnectionString: 'user:wrongpassword'},
 * })
 * // returns a `Left` - service.dbConnectionString expected "user:pass", but got "user:wrongpassword"
 */
export declare const narrow: <C extends Any, D extends Any>(codec: C, predicate: (value: TypeOf<C>, context: Context) => boolean | D, name?: string) => RefinementC<C>;
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