mobx-keystone-mindreframer/src/typeChecking/maybe.ts

A MobX powered state management solution based on data trees with first class support for Typescript, snapshots, patches and much more

import { typesOr } from "./or"
import { typesNull, typesUndefined } from "./primitives"
import type { AnyType, IdentityType } from "./schemas"

/**
 * A type that represents either a type or undefined.
 * Syntactic sugar for `types.or(baseType, types.undefined)`
 *
 * Example:
 * ```ts
 * const numberOrUndefinedType = types.maybe(types.number)
 * ```
 *
 * @typeparam T Type.
 * @param baseType Type.
 * @returns
 */
export function typesMaybe<T extends AnyType>(baseType: T): T | IdentityType<undefined> {
  return typesOr(baseType, typesUndefined)
}

/**
 * A type that represents either a type or null.
 * Syntactic sugar for `types.or(baseType, types.null)`
 *
 *  * Example:
 * ```ts
 * const numberOrNullType = types.maybeNull(types.number)
 * ```
 *
 * @typeparam T Type.
 * @param type Type.
 * @returns
 */
export function typesMaybeNull<T extends AnyType>(type: T): T | IdentityType<null> {
  return typesOr(type, typesNull)
}