A library for safer and smarter error- and "nothing"-handling in TypeScript.
.value (@chriskrycho)null and undefined (@chriskrycho)Result.ok() (@chriskrycho)Result.ok() (@chriskrycho)main and next with Dependabot (@chriskrycho)true-myth/toolbelt module for better tree shaking (@chriskrycho)package.json to exports (@chriskrycho)package.json to exports by @chriskrycho in https://github.com/true-myth/true-myth/pull/243
Full Changelog: https://github.com/true-myth/true-myth/compare/v5.0.0...v5.0.1
The top-level namespace-style export has been removed. If you were relying on the static members to be present when doing import Maybe from 'true-myth/maybe' or import Result from 'true-myth/result';, you can replace them with import * as Maybe from 'true-myth/maybe'; or import * as Result from 'true-myth/result';. This should make for much better tree-shaking with bundlers like Rollup, which can see “through” a namespace import in a way they cannot with a manually-created namespace object. Where you want to maintain the type and namespace imports, you can do this:
import * as Maybe from 'true-myth/maybe';
type Maybe<T> = Maybe.Maybe<T>; // convenience alias
In general, though, you should prefer to simply import the named functions instead:
import Maybe, { transposeArray } from 'true-myth/maybe';
There are no longer separate classes for Just, Nothing, Ok, and Err. This substantially reduces the size of the library, and should hopefully improve browsers' ability to optimize code using these, since there is now only one class in each case: Maybe and Result. The public API for the classes is unchanged, but if you relied on instanceof checks against those classes anywhere, those checks will no longer work.
The exported Variant types are now frozen, constant objects, not TypeScript enums. This should not break anyone, since the only difference in observable behavior between an enum and a const is the ability to do a “reverse lookup” on an enum—but since the field names and their values are identical, this just means shipping less, and faster, code.
The isJust, isNothing, isOk, and isErr methods have been converted to getters. This makes them muchmore immediately useful in contexts where invoking a function is annoying, for any reason—for example, in Ember templates.
We no longer publish CommonJS modules, only ES Modules.
Dropped support for Node versions earlier than Node 12 LTS.
Support for versions of TypeScript before 4.0 have been removed, to enable the type-safe re-implementation of Maybe.all.
The MaybeShape and ResultShape interfaces are no longer exported. These were never intended for public reimplementation, and there is accordingly no value in their continuing to be public.
A number of aliases (originally designed to make migration from e.g. Folktale easier) have been removed:
cata: use match
chain and flatMap: use andThen
maybeify and transmogrify: use wrapReturn
unsafelyGet, unsafeGet, and unsafelyUnwrap: use .isJust/.isOk then .value
unsafelyGetErr and unsafelyUnwrapErr: use .isErr then .error
getOr: use unwrapOr
getOrElse: use unwrapOrElse
fromNullable and maybe:
Maybe and use its static constructor Maybe.of
Maybe.of
of and alias it as you likeWe introduced a new Maybe.transposeArray, which is a type-safe, renamed, merged version of Maybe.tuple and Maybe.all which can correctly handle both array and tuple types. To support this change, it now accepts arrays or tuples directly, and the variadic/spread arguments to all have been replaced with taking an array or tuple directly. While tuple and all are unchanged, they are also deprecated (see below).
Before:
import Maybe, { all, just, nothing, tuple } from 'true-myth/maybe';
// arrays
type ArrayResult = Maybe<Array<string | number>>;
let mixedArray = [just("hello"), nothing<number>()];
let mixedArrayResult: ArrayResult = all(...arrayOfMaybes);
let allJustArray = [just("hello"), just(12)];
let allJustArrayResult: ArrayResult = all(...allJustArray);
type Tuple = [Maybe<number>, Maybe<string>];
type TupleResult = Maybe<[number, string]>;
let mixedTuple: Tuple = [just(12), just("hi")];
let mixedTupleResult: TupleResult = tuple(mixedTuple);
After:
import Maybe, { arrayTranspose, just, nothing } from 'true-myth/maybe';
// arrays
type ArrayResult = Maybe<Array<string | number>>;
let mixedArray = [just("hello"), nothing<number>()];
let mixedArrayResult: ArrayResult = arrayTranspose(arrayOfMaybes);
let allJustArray = [just("hello"), just(12)];
let allJustArrayResult: ArrayResult = arrayTranspose(allJustArray);
// Tuples now work with `arrayTranspose` as well.
type Tuple = [Maybe<number>, Maybe<string>];
type TupleResult = Maybe<[number, string]>;
let mixedTuple: Tuple = [just(12), just("hi")];
let mixedTupleResult: TupleResult = arrayTranspose(mixedTuple);
Maybe.transpose and Result.transpose: for when you have a Maybe<Result<T, E>> or a Result<Maybe<T>, E> and need to invert them.
import Maybe, { just, nothing } from 'true-myth/maybe';
import Result, { ok, err } from 'true-myth/result';
let anOkJust: Result<Maybe<number>, string> = ok(just(12));
let maybe: Maybe<number>, string> = Maybe.transposeResult(anOkJust);
console.log(maybe); // Just(Ok(12))
let aJustOk: Maybe<Result<number, string>> = just(ok(12));
let result: Maybe<Result<number, string>> = Result.transposeMaybe(aJustOk);
console.log(result); // Ok(Just(12))
See the docs for further details!
Note: these are standalone functions, not methods, because TypeScript does not support conditionally supplying a method only for one specific type parameterization.
Maybe.tuple and Maybe.all are deprecated in favor of Maybe.arrayTranspose now correctly handles both arrays and tuples. They will be removed not earlier than 6.0.0 (timeline not decided, but not sooner than when Node 12 LTS reaches end of life on April 30, 2022).Maybe.all implementation by @chriskrycho in https://github.com/true-myth/true-myth/pull/88
*Shape interface exports by @chriskrycho in https://github.com/true-myth/true-myth/pull/93
any from the codebase by @chriskrycho in https://github.com/true-myth/true-myth/pull/94
engines, fix authors/contributors by @chriskrycho in https://github.com/true-myth/true-myth/pull/121
ap docs about currying by @chriskrycho in https://github.com/true-myth/true-myth/pull/216
transpose handling by @chriskrycho in https://github.com/true-myth/true-myth/pull/219
Full Changelog: https://github.com/true-myth/true-myth/compare/v4.1.1...v5.0.0