ts-toolbelt/out/Function/ValidPath.d.ts

TypeScript's largest utility library

import { IterationOf } from '../Iteration/IterationOf';
import { Iteration } from '../Iteration/Iteration';
import { Next } from '../Iteration/Next';
import { Pos } from '../Iteration/Pos';
import { At } from '../Any/At';
import { Cast } from '../Any/Cast';
import { NonNullable } from '../Union/NonNullable';
import { Update } from '../List/Update';
import { Key } from '../Iteration/Key';
import { Key as AKey } from '../Any/Key';
import { List } from '../List/List';
import { Length } from '../List/Length';
import { Extends } from '../Any/Extends';
/**
 * @hidden
 */
declare type ValidatePath<O, Path extends List<AKey>, I extends Iteration> = Update<Path, Key<I>, [
    At<O & {}, Path[Pos<I>]>
] extends [never] ? keyof O : Path[Pos<I>]>;
/**
 * @hidden
 */
declare type __ValidPath<O, Path extends List<AKey>, I extends Iteration = IterationOf<0>> = {
    0: __ValidPath<NonNullable<At<O & {}, Path[Pos<I>]>>, ValidatePath<O, Path, I>, Next<I>>;
    1: Path;
}[Extends<Pos<I>, Length<Path>>];
/**
 * @hidden
 */
export declare type _ValidPath<O extends object, Path extends List<AKey>> = __ValidPath<O, Path> extends infer X ? Cast<X, List<AKey>> : never;
/**
 * Replaces invalid parts of a path with `never`
 * @param O to be inspected
 * @param Path to be validated
 * @returns [[Index]][]
 * @example
 * ```ts
 * import {A, L, O} from 'ts-toolbelt'
 *
 * // Get a property in an object `o` at any depth with `path`
 * // `A.Cast<P, O.ValidPath<O, P>>` makes sure `path` is valid
 * const getAt = <
 * O extends object,
 * P extends L.List<A.Index>
 * >(o: O, path: A.Cast<P, O.ValidPath<O, P>>): O.Path<O, P> => {
 *     let valueAt = o
 *
 *     for (const p of path)
 *         valueAt = valueAt[p]
 *
 *     return valueAt as any
 * }
 *
 * const test0 = getAt({a: {b: {c: 1}}},          ['a', 'b'] as const) // {c: number}
 * const test1 = getAt({a: {b: {c: 1}}} as const, ['a', 'b'] as const) // {c: 1}
 * const test2 = getAt({a: {b: {c: 1}}},          ['x'] as const)      // error
 * ```
 */
export declare type ValidPath<O extends object, Path extends List<AKey>> = O extends unknown ? Path extends unknown ? _ValidPath<O, Path> : never : never;
export {};