io-ts-extra/dist/narrow.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.narrow = void 0;
const io_ts_1 = require("io-ts");
const Either_1 = require("fp-ts/lib/Either");
const chain = Either_1.either.chain;
/**
 * 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"
 */
const narrow = (codec, predicate, name = `(${codec.name} | ${io_ts_1.getFunctionName(predicate)})`) => {
    return new io_ts_1.RefinementType(name, (u) => {
        if (!codec.is(u)) {
            return false;
        }
        const refined = predicate(u, []);
        if (refined instanceof io_ts_1.Type) {
            return refined.is(u);
        }
        return refined;
    }, (i, c) => chain(codec.validate(i, c), a => {
        const refined = predicate(a, c);
        if (refined instanceof io_ts_1.Type) {
            return refined.validate(a, c);
        }
        if (refined) {
            return io_ts_1.success(a);
        }
        return io_ts_1.failure(a, c);
    }), codec.encode, codec, predicate);
};
exports.narrow = narrow;
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