614 lines
20 KiB
JavaScript
614 lines
20 KiB
JavaScript
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/** [[include:doc/result.md]] */
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/** (keep typedoc from getting confused by the import) */
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import * as Maybe from './maybe';
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import Unit from './unit';
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import { _Brand, curry1, isVoid } from './utils';
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// So that it doesn't appear unused but can be exported.
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_Brand; // tslint:disable-line:no-unused-expression
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/**
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Discriminant for `Ok` and `Err` variants of `Result` type.
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You can use the discriminant via the `variant` property of `Result` instances
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if you need to match explicitly on it.
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*/
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export var Variant;
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(function (Variant) {
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Variant["Ok"] = "Ok";
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Variant["Err"] = "Err";
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})(Variant || (Variant = {}));
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/**
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An `Ok` instance is the *successful* variant instance of the
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[`Result`](../modules/_result_.html#result) type, representing a successful
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outcome from an operation which may fail. For a full discussion, see [the
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module docs](../modules/_result_.html).
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@typeparam T The type wrapped in this `Ok` variant of `Result`.
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@typeparam E The type which would be wrapped in an `Err` variant of `Result`.
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*/
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export class Ok {
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/**
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Create an instance of `Result.Ok` with `new`.
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Note: While you *may* create the `Result` type via normal
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JavaScript class construction, it is not recommended for the functional
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style for which the library is intended. Instead, use [`Result.ok`].
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[`Result.ok`]: ../modules/_result_.html#ok
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```ts
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// Avoid:
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const aString = new Result.Ok('characters');
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// Prefer:
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const aString = Result.ok('characters);
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```
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Note that you may explicitly pass `Unit` to the `Ok` constructor to create
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a `Result<Unit, E>`. However, you may *not* call the `Ok` constructor with
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`null` or `undefined` to get that result (the type system won't allow you to
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construct it that way). Instead, for convenience, you can simply call
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`Result.ok()`, which will construct the type correctly.
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@param value
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The value to wrap in a `Result.Ok`.
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Note: `null` and `undefined` are allowed by the type signature so that the
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constructor may `throw` on those rather than constructing a type like
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`Result<undefined>`.
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@throws If you pass `null`.
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*/
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constructor(value) {
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/** `Ok` is always [`Variant.Ok`](../enums/_result_.variant#ok). */
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this.variant = Variant.Ok;
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if (isVoid(value)) {
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throw new Error('Tried to construct `Ok` with `null` or `undefined`. Maybe you want `Maybe.Nothing`?');
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}
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this.value = value;
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}
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/**
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Unwrap the contained value. A convenience method for functional idioms.
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A common scenario where you might want to use this is in a pipeline of
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functions:
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```ts
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import Result, { Ok } from 'true-myth/result';
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function getLengths(results: Array<Result<string, string>>): Array<number> {
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return results
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.filter(Result.isOk)
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.map(Ok.unwrap)
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.map(s => s.length);
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}
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```
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*/
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static unwrap(theOk) {
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return theOk.value;
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}
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/** Method variant for [`Result.isOk`](../modules/_result_.html#isok) */
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isOk() {
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return true;
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}
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/** Method variant for [`Result.isErr`](../modules/_result_.html#iserr) */
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isErr() {
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return false;
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}
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/** Method variant for [`Result.map`](../modules/_result_.html#map) */
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map(mapFn) {
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return map(mapFn, this);
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}
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/** Method variant for [`Result.mapOr`](../modules/_result_.html#mapor) */
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mapOr(orU, mapFn) {
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return mapOr(orU, mapFn, this);
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}
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/** Method variant for [`Result.mapOrElse`](../modules/_result_.html#maporelse) */
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mapOrElse(orElseFn, mapFn) {
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return mapOrElse(orElseFn, mapFn, this);
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}
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/** Method variant for [`Result.match`](../modules/_result_.html#match) */
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match(matcher) {
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return match(matcher, this);
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}
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/** Method variant for [`Result.mapErr`](../modules/_result_.html#maperr) */
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mapErr(mapErrFn) {
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return mapErr(mapErrFn, this);
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}
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/** Method variant for [`Result.or`](../modules/_result_.html#or) */
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or(orResult) {
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return or(orResult, this);
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}
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/** Method variant for [`Result.orElse`](../modules/_result_.html#orelse) */
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orElse(orElseFn) {
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return orElse(orElseFn, this);
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}
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/** Method variant for [`Result.and`](../modules/_result_.html#and) */
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and(mAnd) {
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return and(mAnd, this);
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}
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/** Method variant for [`Result.andThen`](../modules/_result_.html#andthen) */
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andThen(andThenFn) {
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return andThen(andThenFn, this);
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}
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/** Method variant for [`Result.chain`](../modules/_result_.html#chain) */
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chain(chainFn) {
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return chain(chainFn, this);
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}
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/** Method variant for [`Result.flatMap`](../modules/_result_.html#flatmap) */
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flatMap(flatMapFn) {
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return flatMap(flatMapFn, this);
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}
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/** Method variant for [`Result.unwrap`](../modules/_result_.html#unwrap) */
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unsafelyUnwrap() {
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return this.value;
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}
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/** Method variant for [`Result.unwrapErr`](../modules/_result_.html#unwraperr) */
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unsafelyUnwrapErr() {
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throw new Error('Tried to `unsafelyUnwrapErr` an `Ok`');
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}
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/** Method variant for [`Result.unwrapOr`](../modules/_result_.html#unwrapor) */
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unwrapOr(defaultValue) {
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return unwrapOr(defaultValue, this);
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}
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/** Method variant for [`Result.unwrapOrElse`](../modules/_result_.html#unwrapOrElse) */
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unwrapOrElse(elseFn) {
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return unwrapOrElse(elseFn, this);
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}
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/** Method variant for [`Result.toMaybe`](../modules/_result_.html#tomaybe) */
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toMaybe() {
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return toMaybe(this);
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}
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/** Method variant for [`Result.toString`](../modules/_result_.html#tostring) */
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toString() {
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return toString(this);
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}
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/** Method variant for [`Result.toJSON`](../modules/_result_.html#toJSON) */
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toJSON() {
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return toJSON(this);
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}
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/** Method variant for [`Result.equals`](../modules/_result_.html#equals) */
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equals(comparison) {
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return equals(comparison, this);
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}
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/** Method variant for [`Result.ap`](../modules/_result_.html#ap) */
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ap(r) {
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return ap(this, r);
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}
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}
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/**
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An `Err` instance is the *failure* variant instance of the
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[`Result`](../modules/_result_.html#result) type, representing a failure
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outcome from an operation which may fail. For a full discussion, see [the
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module docs](../modules/_result_.html).
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@typeparam T The type which would be wrapped in an `Ok` variant of `Result`.
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@typeparam E The type wrapped in this `Err` variant of `Result`.
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*/
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export class Err {
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/**
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Create an instance of `Result.Err` with `new`.
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Note: While you *may* create the `Result` type via normal
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JavaScript class construction, it is not recommended for the functional
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style for which the library is intended. Instead, use [`Result.err`].
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[`Result.err`]: ../modules/_result_.html#err
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```ts
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// Avoid:
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const anErr = new Result.Err('alas, failure');
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// Prefer:
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const anErr = Result.err('alas, failure');
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```
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Note that you may explicitly pass `Unit` to the `Err` constructor to create
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a `Result<T, Unit>`. However, you may *not* call the `Err` constructor with
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`null` or `undefined` to get that result (the type system won't allow you to
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construct it that way). Instead, for convenience, you can simply call
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`Result.err()`, which will construct the type correctly.
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@param error
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The value to wrap in a `Result.Err`.
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`Note: null` and `undefined` are allowed by the type signature so that the
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constructor may `throw` on those rather than constructing a type like
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`Result<number, undefined>`.
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@throws If you pass `null` or `undefined`.
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*/
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constructor(error) {
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/** `Err` is always [`Variant.Err`](../enums/_result_.variant#err). */
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this.variant = Variant.Err;
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if (isVoid(error)) {
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throw new Error('Tried to construct `Err` with `null` or `undefined`. Maybe you want `Maybe.Nothing`?');
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}
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this.error = error;
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}
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/**
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Unwrap the contained error . A convenience method for functional idioms.
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A common scenario where you might want to use this is in a pipeline of
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functions:
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```ts
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import Result, { Ok } from 'true-myth/result';
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function getMessages(results: Array<Result<string, Error>>): Array<number> {
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return maybeStrings
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.filter(Result.isErr)
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.map(Err.unwrapErr)
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.map(e => e.message);
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}
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```
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*/
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static unwrapErr(theErr) {
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return theErr.error;
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}
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/** Method variant for [`Result.isOk`](../modules/_result_.html#isok) */
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isOk() {
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return false;
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}
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/** Method variant for [`Result.isErr`](../modules/_result_.html#iserr) */
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isErr() {
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return true;
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}
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/** Method variant for [`Result.map`](../modules/_result_.html#map) */
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map(mapFn) {
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return map(mapFn, this);
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}
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/** Method variant for [`Result.mapOr`](../modules/_result_.html#mapor) */
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mapOr(orU, mapFn) {
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return mapOr(orU, mapFn, this);
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}
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/** Method variant for [`Result.mapOrElse`](../modules/_result_.html#maporelse) */
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mapOrElse(orElseFn, mapFn) {
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return mapOrElse(orElseFn, mapFn, this);
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}
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/** Method variant for [`Result.match`](../modules/_result_.html#match) */
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match(matchObj) {
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return match(matchObj, this);
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}
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/** Method variant for [`Result.mapErr`](../modules/_result_.html#maperr) */
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mapErr(mapErrFn) {
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return mapErr(mapErrFn, this);
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}
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/** Method variant for [`Result.or`](../modules/_result_.html#or) */
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or(orResult) {
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return or(orResult, this);
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}
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/** Method variant for [`Result.orElse`](../modules/_result_.html#orelse) */
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orElse(orElseFn) {
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return orElse(orElseFn, this);
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}
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/** Method variant for [`Result.and`](../modules/_result_.html#and) */
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and(mAnd) {
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return and(mAnd, this);
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}
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/** Method variant for [`Result.andThen`](../modules/_result_.html#andthen) */
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andThen(andThenFn) {
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return andThen(andThenFn, this);
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}
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/** Method variant for [`Result.chain`](../modules/_result_.html#chain) */
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chain(chainFn) {
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return this.andThen(chainFn);
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}
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/** Method variant for [`Result.flatMap`](../modules/_result_.html#flatmap) */
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flatMap(flatMapFn) {
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return this.andThen(flatMapFn);
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}
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/** Method variant for [`Result.unsafelyUnwrap`](../modules/_result_.html#unsafelyunwrap) */
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unsafelyUnwrap() {
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throw new Error('Tried to `unsafelyUnwrap an Err`');
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}
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/** Method variant for [`Result.unsafelyUnwrapErr`](../modules/_result_.html#unsafelyunwraperr) */
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unsafelyUnwrapErr() {
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return this.error;
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}
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/** Method variant for [`Result.unwrapOr`](../modules/_result_.html#unwrapor) */
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unwrapOr(defaultValue) {
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return unwrapOr(defaultValue, this);
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}
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/** Method variant for [`Result.unwrapOrElse`](../modules/_result_.html#unwraporelse) */
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unwrapOrElse(elseFn) {
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return unwrapOrElse(elseFn, this);
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}
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/** Method variant for [`Result.toMaybe`](../modules/_result_.html#tomaybe) */
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toMaybe() {
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return toMaybe(this);
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}
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/** Method variant for [`Result.toString`](../modules/_result_.html#tostring) */
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toString() {
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return toString(this);
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}
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/** Method variant for [`Result.toJSON`](../modules/_result_.html#toJSON) */
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toJSON() {
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return toJSON(this);
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}
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/** Method variant for [`Result.equals`](../modules/_result_.html#equals) */
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equals(comparison) {
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return equals(comparison, this);
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}
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/** Method variant for [`Result.ap`](../modules/_result_.html#ap) */
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ap(r) {
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return ap(this, r);
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}
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}
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/**
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Is this `Result` an `Ok` instance?
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In TypeScript, narrows the type from `Result<T, E>` to `Ok<T, E>`.
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*/
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export function isOk(result) {
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return result.variant === Variant.Ok;
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}
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/**
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Is this `Result` an `Err` instance?
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In TypeScript, narrows the type from `Result<T, E>` to `Err<T, E>`.
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*/
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export function isErr(result) {
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return result.variant === Variant.Err;
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}
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export function ok(value) {
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return value === undefined ? new Ok(Unit) : new Ok(value);
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}
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/** `Result.of` is an alias for `Result.ok`. */
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export const of = ok;
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export function err(error) {
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return isVoid(error) ? new Err(Unit) : new Err(error);
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}
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|
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export function tryOr(error, callback) {
|
||
|
|
const op = (cb) => {
|
||
|
|
try {
|
||
|
|
return Result.ok(cb());
|
||
|
|
}
|
||
|
|
catch (_a) {
|
||
|
|
return Result.err(error);
|
||
|
|
}
|
||
|
|
};
|
||
|
|
return curry1(op, callback);
|
||
|
|
}
|
||
|
|
export function tryOrElse(onError, callback) {
|
||
|
|
const op = (cb) => {
|
||
|
|
try {
|
||
|
|
return Result.ok(cb());
|
||
|
|
}
|
||
|
|
catch (e) {
|
||
|
|
return Result.err(onError(e));
|
||
|
|
}
|
||
|
|
};
|
||
|
|
return curry1(op, callback);
|
||
|
|
}
|
||
|
|
export function map(mapFn, result) {
|
||
|
|
const op = (r) => (isOk(r) ? ok(mapFn(r.value)) : r);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
export function mapOr(orU, mapFn, result) {
|
||
|
|
function fullOp(fn, r) {
|
||
|
|
return isOk(r) ? fn(r.value) : orU;
|
||
|
|
}
|
||
|
|
function partialOp(fn, curriedResult) {
|
||
|
|
return curriedResult !== undefined
|
||
|
|
? fullOp(fn, curriedResult)
|
||
|
|
: (extraCurriedResult) => fullOp(fn, extraCurriedResult);
|
||
|
|
}
|
||
|
|
return mapFn === undefined
|
||
|
|
? partialOp
|
||
|
|
: result === undefined
|
||
|
|
? partialOp(mapFn)
|
||
|
|
: partialOp(mapFn, result);
|
||
|
|
}
|
||
|
|
export function mapOrElse(orElseFn, mapFn, result) {
|
||
|
|
function fullOp(fn, r) {
|
||
|
|
return isOk(r) ? fn(r.value) : orElseFn(r.error);
|
||
|
|
}
|
||
|
|
function partialOp(fn, curriedResult) {
|
||
|
|
return curriedResult !== undefined
|
||
|
|
? fullOp(fn, curriedResult)
|
||
|
|
: (extraCurriedResult) => fullOp(fn, extraCurriedResult);
|
||
|
|
}
|
||
|
|
return mapFn === undefined
|
||
|
|
? partialOp
|
||
|
|
: result === undefined
|
||
|
|
? partialOp(mapFn)
|
||
|
|
: partialOp(mapFn, result);
|
||
|
|
}
|
||
|
|
export function mapErr(mapErrFn, result) {
|
||
|
|
const op = (r) => (isOk(r) ? r : err(mapErrFn(r.error)));
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
export function and(andResult, result) {
|
||
|
|
const op = (r) => (isOk(r) ? andResult : r);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
export function andThen(thenFn, result) {
|
||
|
|
const op = (r) => (isOk(r) ? thenFn(r.value) : r);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/** Alias for [`andThen`](#andthen). */
|
||
|
|
export const chain = andThen;
|
||
|
|
/** Alias for [`andThen`](#andthen). */
|
||
|
|
export const flatMap = andThen;
|
||
|
|
export function or(defaultResult, result) {
|
||
|
|
const op = (r) => (isOk(r) ? r : defaultResult);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
export function orElse(elseFn, result) {
|
||
|
|
const op = (r) => (isOk(r) ? r : elseFn(r.unsafelyUnwrapErr()));
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
Get the value out of the `Result`.
|
||
|
|
|
||
|
|
Returns the content of an `Ok`, but **throws if the `Result` is `Err`.**
|
||
|
|
Prefer to use [`unwrapOr`](#unwrapor) or [`unwrapOrElse`](#unwraporelse).
|
||
|
|
|
||
|
|
@throws If the `Result` instance is `Nothing`.
|
||
|
|
*/
|
||
|
|
export function unsafelyUnwrap(result) {
|
||
|
|
return result.unsafelyUnwrap();
|
||
|
|
}
|
||
|
|
/** Alias for [`unsafelyUnwrap`](#unsafelyunwrap) */
|
||
|
|
export const unsafelyGet = unsafelyUnwrap;
|
||
|
|
/** Alias for [`unsafelyUnwrap`](#unsafelyunwrap) */
|
||
|
|
export const unsafeGet = unsafelyUnwrap;
|
||
|
|
/**
|
||
|
|
Get the error value out of the [`Result`](#result).
|
||
|
|
|
||
|
|
Returns the content of an `Err`, but **throws if the `Result` is `Ok`**.
|
||
|
|
Prefer to use [`unwrapOrElse`](#unwraporelse).
|
||
|
|
|
||
|
|
@param result
|
||
|
|
@throws Error If the `Result` instance is `Nothing`.
|
||
|
|
*/
|
||
|
|
export function unsafelyUnwrapErr(result) {
|
||
|
|
return result.unsafelyUnwrapErr();
|
||
|
|
}
|
||
|
|
/** Alias for [`unsafelyUnwrapErr`](#unsafelyunwraperr) */
|
||
|
|
export const unsafelyGetErr = unsafelyUnwrapErr;
|
||
|
|
export function unwrapOr(defaultValue, result) {
|
||
|
|
const op = (r) => (isOk(r) ? r.value : defaultValue);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/** Alias for [`unwrapOr`](#unwrapor) */
|
||
|
|
export const getOr = unwrapOr;
|
||
|
|
export function unwrapOrElse(orElseFn, result) {
|
||
|
|
const op = (r) => (isOk(r) ? r.value : orElseFn(r.error));
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/** Alias for [`unwrapOrElse`](#unwraporelse) */
|
||
|
|
export const getOrElse = unwrapOrElse;
|
||
|
|
/**
|
||
|
|
Convert a [`Result`](#result) to a [`Maybe`](../modules/_maybe_.html#maybe).
|
||
|
|
|
||
|
|
The converted type will be [`Just`] if the `Result` is [`Ok`] or [`Nothing`]
|
||
|
|
if the `Result` is [`Err`]; the wrapped error value will be discarded.
|
||
|
|
|
||
|
|
[`Just`]: ../classes/_maybe_.just.html
|
||
|
|
[`Nothing`]: ../classes/_maybe_.nothing.html
|
||
|
|
[`Ok`]: ../classes/_result_.ok.html
|
||
|
|
[`Err`]: ../classes/_result_.err.html
|
||
|
|
|
||
|
|
@param result The `Result` to convert to a `Maybe`
|
||
|
|
@returns `Just` the value in `result` if it is `Ok`; otherwise `Nothing`
|
||
|
|
*/
|
||
|
|
export function toMaybe(result) {
|
||
|
|
return isOk(result) ? Maybe.just(result.value) : Maybe.nothing();
|
||
|
|
}
|
||
|
|
export function fromMaybe(errValue, maybe) {
|
||
|
|
const op = (m) => Maybe.isJust(m) ? ok(Maybe.unsafelyUnwrap(m)) : err(errValue);
|
||
|
|
return curry1(op, maybe);
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
Create a `String` representation of a `result` instance.
|
||
|
|
|
||
|
|
An `Ok` instance will be printed as `Ok(<representation of the value>)`, and
|
||
|
|
an `Err` instance will be printed as `Err(<representation of the error>)`,
|
||
|
|
where the representation of the value or error is simply the value or error's
|
||
|
|
own `toString` representation. For example:
|
||
|
|
|
||
|
|
call | output
|
||
|
|
--------------------------------- | ----------------------
|
||
|
|
`toString(ok(42))` | `Ok(42)`
|
||
|
|
`toString(ok([1, 2, 3]))` | `Ok(1,2,3)`
|
||
|
|
`toString(ok({ an: 'object' }))` | `Ok([object Object])`n
|
||
|
|
`toString(err(42))` | `Err(42)`
|
||
|
|
`toString(err([1, 2, 3]))` | `Err(1,2,3)`
|
||
|
|
`toString(err({ an: 'object' }))` | `Err([object Object])`
|
||
|
|
|
||
|
|
@typeparam T The type of the wrapped value; its own `.toString` will be used
|
||
|
|
to print the interior contents of the `Just` variant.
|
||
|
|
@param maybe The value to convert to a string.
|
||
|
|
@returns The string representation of the `Maybe`.
|
||
|
|
*/
|
||
|
|
export const toString = (result) => {
|
||
|
|
const body = (isOk(result) ? result.value : result.error).toString();
|
||
|
|
return `${result.variant.toString()}(${body})`;
|
||
|
|
};
|
||
|
|
/**
|
||
|
|
* Create an `Object` representation of a `Result` instance.
|
||
|
|
*
|
||
|
|
* Useful for serialization. `JSON.stringify()` uses it.
|
||
|
|
*
|
||
|
|
* @param result The value to convert to JSON
|
||
|
|
* @returns The JSON representation of the `Result`
|
||
|
|
*/
|
||
|
|
export const toJSON = (result) => {
|
||
|
|
return result.isOk()
|
||
|
|
? { variant: result.variant, value: result.value }
|
||
|
|
: { variant: result.variant, error: result.error };
|
||
|
|
};
|
||
|
|
export function match(matcher, result) {
|
||
|
|
const op = (r) => mapOrElse(matcher.Err, matcher.Ok, r);
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/** Alias for [`match`](#match) */
|
||
|
|
export const cata = match;
|
||
|
|
export function equals(resultB, resultA) {
|
||
|
|
return resultA !== undefined
|
||
|
|
? resultA.match({
|
||
|
|
Err: () => isErr(resultB),
|
||
|
|
Ok: a => isOk(resultB) && resultB.unsafelyUnwrap() === a,
|
||
|
|
})
|
||
|
|
: (curriedResultA) => curriedResultA.match({
|
||
|
|
Err: () => isErr(resultB),
|
||
|
|
Ok: a => isOk(resultB) && resultB.unsafelyUnwrap() === a,
|
||
|
|
});
|
||
|
|
}
|
||
|
|
export function ap(resultFn, result) {
|
||
|
|
const op = (r) => r.match({
|
||
|
|
Ok: val => resultFn.map(fn => fn(val)),
|
||
|
|
Err: e => Result.err(e),
|
||
|
|
});
|
||
|
|
return curry1(op, result);
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
Determine whether an item is an instance of `Just` or `Nothing`.
|
||
|
|
|
||
|
|
@param item The item to check.
|
||
|
|
*/
|
||
|
|
export function isInstance(item) {
|
||
|
|
return item instanceof Ok || item instanceof Err;
|
||
|
|
}
|
||
|
|
export const Result = {
|
||
|
|
Variant,
|
||
|
|
Ok,
|
||
|
|
Err,
|
||
|
|
isOk,
|
||
|
|
isErr,
|
||
|
|
ok,
|
||
|
|
err,
|
||
|
|
tryOr,
|
||
|
|
tryOrElse,
|
||
|
|
map,
|
||
|
|
mapOr,
|
||
|
|
mapOrElse,
|
||
|
|
mapErr,
|
||
|
|
and,
|
||
|
|
andThen,
|
||
|
|
chain,
|
||
|
|
flatMap,
|
||
|
|
or,
|
||
|
|
orElse,
|
||
|
|
unsafelyUnwrap,
|
||
|
|
unsafelyGet,
|
||
|
|
unsafeGet,
|
||
|
|
unsafelyUnwrapErr,
|
||
|
|
unsafelyGetErr,
|
||
|
|
unwrapOr,
|
||
|
|
getOr,
|
||
|
|
unwrapOrElse,
|
||
|
|
getOrElse,
|
||
|
|
toMaybe,
|
||
|
|
fromMaybe,
|
||
|
|
toString,
|
||
|
|
toJSON,
|
||
|
|
match,
|
||
|
|
cata,
|
||
|
|
equals,
|
||
|
|
ap,
|
||
|
|
isInstance,
|
||
|
|
};
|
||
|
|
export default Result;
|
||
|
|
//# sourceMappingURL=result.js.map
|