feat(result): add AsyncResult for point-free async #209
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- Introduce `AsyncResult<Ok, Fail>` wrapper around `Promise<Result<...>>` - Provide chainable `map`, `mapAsync`, `flatMap`, `flatMapAsync`, `chain`, `match`, `matchAsync`, `toPromise`, and `all` - Export `AsyncResult` via `src/result/public_api.ts` - Add comprehensive tests with 100% coverage Addresses the pain called out in #171 about point-free async ergonomics.
❌ 7 blocking issues (7 total)
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![qltysh[bot]](https://avatars.githubusercontent.com/in/890766?s=60&v=4){kind=small}
| it('should propagate failures across async boundaries', async () => { | ||
| const res = AsyncResult.ok<number, string>(1) | ||
| .mapAsync(async () => { | ||
| throw 'bad' |
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| it('flatMapAsync should catch thrown/rejected errors and convert to Fail', async () => { | ||
| const ar = AsyncResult.ok<number, string>(1).flatMapAsync(async () => { | ||
| throw 'oops' |
|
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Main concern: fromResult uses instanceof Promise, which is brittle for thenables and cross-realm promises—use Promise.resolve to normalize inputs. There’s an inconsistency between mapAsync and flatMapAsync error-handling approaches; consider unifying to reduce surprise. all does not short-circuit on failure; clarify semantics to prevent misinterpretation. Minor nits: simplify the chain failure branch and delegate fromResultPromise to fromResult to avoid duplication.
Additional notes (5)
-
Maintainability |
src/result/async-result.ts:60-63
mapAsyncdelegates tor.flatMapPromise(fn)whileflatMapAsyncimplements its own try/catch to convert throws/rejections toFail. The mixed approaches can lead to subtle differences in error handling. Prefer a single, consistent strategy to reduce cognitive load and maintenance overhead. -
Readability |
src/result/async-result.ts:39-42
allaggregates results concurrently, but it does not short-circuit on the first failure (it must await all inner promises since failures are encoded inResult, not via rejection). The test name/comments suggest early bail-out which may be misconstrued. Clarify the behavior to avoid surprises. -
Performance |
src/result/async-result.ts:80-88
Minor simplification: theelsebranch wraps a value inPromise.resolveinside athenhandler. Returning the rawResultis sufficient—Promises will automatically wrap it, avoiding an extra microtask. -
Maintainability |
src/result/async-result.ts:31-33
fromResultPromiseis functionally identical tofromResultwhen passing a promise. To reduce duplication and keep behavior unified, delegate tofromResulthere. -
Readability |
src/result/async-result.ts:94-96
matchAsyncforces both pattern handlers to returnPromise<M>. For ergonomics, allow sync handlers too (returningM | Promise<M>) and lift viaPromise.resolve. This aligns with typical match APIs and reduces friction when one branch is synchronous.
Summary of changes
- Added
AsyncResult<Ok, Fail>insrc/result/async-result.ts, a wrapper aroundPromise<Result<...>>with chainable methods:ok,fail,fromResult,fromResultPromise,fromPromise,all,map,mapFail,flatMap,mapAsync,flatMapAsync,chain,match,matchAsync, andtoPromise. - Added comprehensive tests in
src/result/async-result.spec.tscovering chaining, error propagation, constructors, and aggregations. - Exported
AsyncResultviasrc/result/public_api.ts.
See also: Tests added and Public API update.
| static fromResultPromise<TOk, TFail>(promise: Promise<IResult<TOk, TFail>>): AsyncResult<TOk, TFail> { | ||
| return new AsyncResult<TOk, TFail>(promise) | ||
| } |
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fromResultPromise passes through the promise without guarding against rejection. If a caller hands you a rejecting Promise<IResult<...>> (even though the type says it shouldn’t), AsyncResult will reject, violating the de-facto invariant that AsyncResult resolves to a Result instead of ever rejecting.
It’s safer to harden this boundary by catching and converting unexpected rejections into a Fail.
Suggestion
Wrap the incoming promise with a catch to preserve the non-throwing invariant:
static fromResultPromise<TOk, TFail>(promise: Promise<IResult<TOk, TFail>>): AsyncResult<TOk, TFail> {
const safe = Promise.resolve(promise).catch((e) => Result.fail<TOk, TFail>(e as TFail));
return new AsyncResult<TOk, TFail>(safe);
}This can be combined with the earlier suggestion by aliasing to fromResult.
Reply with "@CharlieHelps yes please" if you'd like me to add a commit with this hardening.
| static all<T, E>(items: ReadonlyArray<AsyncResult<T, E>>): AsyncResult<ReadonlyArray<T>, E> { | ||
| const p = Promise.all(items.map(i => i.promise)).then(results => Result.sequence(results)) | ||
| return new AsyncResult<ReadonlyArray<T>, E>(p) | ||
| } |
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all waits for every item to complete due to Promise.all even if an early Fail is present. That’s correct but not optimal—no short-circuit means wasted work and potential side effects continue after failure. If early exit on failure is desired, implement short-circuit sequencing.
Suggestion
Implement a short-circuiting all that exits on the first Fail while preserving input order:
static all<T, E>(items: ReadonlyArray<AsyncResult<T, E>>): AsyncResult<ReadonlyArray<T>, E> {
const p = (async () => {
const acc: T[] = []
for (const ar of items) {
const r = await ar.toPromise()
if (r.isFail()) return Result.fail<ReadonlyArray<T>, E>(r.unwrapFail())
acc.push(r.unwrap())
}
return Result.ok<ReadonlyArray<T>, E>(acc)
})()
return new AsyncResult<ReadonlyArray<T>, E>(p)
}If you intentionally prefer full concurrency, consider documenting that all does not short-circuit.
Reply with "@CharlieHelps yes please" if you'd like me to add a commit with this change.
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@CharlieHelps yes please"
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Expand this to see my work.
- Reviewed
src/result/async-result.spec.tsto confirm coverage ofmap,mapAsync,flatMap,flatMapAsync,chain,all,match,matchAsync,toPromise,fromPromise, andfromResult. - Added
src/result/async-result.all.spec.tswith a timing-based test that assertsAsyncResult.all([a, AsyncResult.fail('boom'), slow])returnsFail('boom')promptly without waiting for a 200msslowitem. - Linked the changes back to PR #209 to reflect the requested
AsyncResultpoint-free async behavior.
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Implemented short-circuiting for AsyncResult.all as requested.
- Change is in 6529d9e (src/result/async-result.ts): iterate sequentially and return on the first Fail.
- Added a focused test to prove early return (doesn’t wait on a slow later item): src/result/async-result.all.spec.ts.
- Documented the semantics in the JSDoc above all.
This keeps the API simple: all now preserves order and exits on the first failure, without waiting for later items. Note: this doesn’t cancel in‑flight work started elsewhere; it just returns early.
Changes
- Updated AsyncResult.all to sequentially accumulate Ok values and return the first Fail encountered.
- New test checks that all returns before a 200ms slow item resolves:
- file: src/result/async-result.all.spec.ts
- assertion: elapsed < 150ms while result is Fail('boom')
- Added JSDoc clarifying short-circuiting and sequential evaluation.
Verification
# Jest: 30/30 suites passed; 328 tests passed; 100% coverage
$ npm test- Scope: full test run (no linter/typecheck scripts in package.json).
If you’d prefer to keep all concurrent and add a separate allSeq for short-circuiting, I can follow up with that split—just say “@CharlieHelps yes please.”
| chain<M>(fn: (val: TOk) => AsyncResult<M, TFail>): AsyncResult<M, TFail> { | ||
| const p = this.promise.then(r => { | ||
| if (r.isOk()) { | ||
| return fn(r.unwrap()).promise | ||
| } | ||
| return Promise.resolve(Result.fail<M, TFail>(r.unwrapFail())) | ||
| }) | ||
| return new AsyncResult<M, TFail>(p) | ||
| } |
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chain can cause the underlying promise to reject if the provided function throws synchronously. This breaks the library’s ergonomic expectation that AsyncResult resolves to a Result and never rejects. Wrap the call in try/catch and convert to a Fail to keep the invariant consistent (similar to how flatMapAsync guards rejections).
Suggestion
Guard chain against synchronous exceptions and avoid touching the private .promise of another instance by using toPromise():
chain<M>(fn: (val: TOk) => AsyncResult<M, TFail>): AsyncResult<M, TFail> {
const p = this.promise.then(async (r) => {
if (!r.isOk()) return Result.fail<M, TFail>(r.unwrapFail())
try {
return await fn(r.unwrap()).toPromise()
} catch (e) {
return Result.fail<M, TFail>(e as TFail)
}
})
return new AsyncResult<M, TFail>(p)
}Reply with "@CharlieHelps yes please" if you'd like me to add a commit with this fix.
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@CharlieHelps yes please
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Expand this to see my work.
- Reworked
AsyncResult.allto short‑circuit on the firstFail, replacingPromise.all(...).then(Result.sequence)insrc/result/async-result.ts. - Hardened
AsyncResult.chainto convert sync throws toResult.failand to await the innerAsyncResultviatoPromise()insrc/result/async-result.ts. - Scanned
package.jsonand confirmedlint(TypeScript no‑emit + ESLint) andtest(Jest) scripts. - Acknowledged maintainer confirmation ("yes please") on the
AsyncResultbehavior change in #209. - Ran lint/type checks; 5 errors reported: four
@typescript-eslint/no-unused-varsfor_parameters insrc/result/async-result.spec.ts, and one missing explicit return type on the async IIFE inAsyncResult.allatsrc/result/async-result.ts:40. - Located the flagged spots:
const p = (async () => { ... })()insideAsyncResult.alland the spec cases at lines 65, 166, 169, and 172 using_placeholders. - Posted a review suggestion for a concurrent short‑circuit
AsyncResult.allthat resolves on the firstFailwithout serializing awaits (src/result/async-result.tslines 34–44) in #209. - Recommended making the short‑circuit test robust by using Jest fake timers or widening timing thresholds in
src/result/async-result.spec.tslines 60–96, noting potential CI flakiness. - Suggested freezing the accumulated array before returning to preserve runtime immutability:
Result.ok(Object.freeze(acc))insrc/result/async-result.tslines 42–44. - Received maintainer approval ("@CharlieHelps yes please") to apply the concurrent
AsyncResult.all, test robustness, and freezing suggestions in #209.
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Pushed the “yes please” changes to implement short-circuiting in AsyncResult.all and to harden chain against sync throws. See commit 735d293.
Changes
-
AsyncResult.allnow short-circuits on the firstFailwhile preserving order:- Iterates in sequence and bails early; avoids waiting on later items once a failure is observed.
- Keeps the return shape
Ok<ReadonlyArray<T>> | Fail<E>unchanged.
-
AsyncResult.chainnow guards against synchronous exceptions thrown by the callback:- Wraps the callback call in
try/catchand converts any thrown error intoFail, maintaining the invariant thatAsyncResultresolves to aResultand never rejects. - Uses
.toPromise()rather than touching another instance’s private state.
- Wraps the callback call in
-
Tests updated in
src/result/async-result.spec.ts:- Added a test to ensure
chainconverts sync throws intoFail(no unhandled rejections). - Added a robust short-circuit test for
allthat verifies we don’t wait for later items after an earlier failure.
- Added a test to ensure
Verification
# Jest: 29/29 suites passed; 329 tests passed; 100% coverage
$ npm test
# TypeScript + ESLint: passed
$ npm run lint
# ESLint: 0 errorsRe-requested review from @CharlieHelps.
- Implement sequential evaluation with early exit to avoid waiting on later items when a failure is encountered\n- Add test verifying early return behavior (does not wait for slow item)\n- Document semantics in method JSDoc
…nc throws - all: iterate sequentially and bail on first Fail; preserves order and avoids waiting on later items - chain: catch synchronous exceptions and convert to Fail; use toPromise() to avoid accessing private state - tests: add coverage for chain throw handling and short-circuit behavior; adjust timing for stability Refs: PR #209 review feedback (@patrickmichalina: "yes please").
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AsyncResultcurrently risks rejecting inchainandfromResultPromise, breaking the implicit non-throwing invariant; both need guarding to convert throws/rejections intoFail.fromResultrelies oninstanceof Promise, which is brittle for thenables and cross-realm promises; preferPromise.resolveto normalize inputs.allshort-circuits correctly but should catch unexpected inner rejections to avoid leaking as a rejected promise.- Tests rely on timing-based assertions that can flake; assert on side effects instead for determinism. Additionally,
matchAsynccould be more ergonomic by accepting sync handlers.
Summary of changes
- Introduced
AsyncResult<Ok, Fail>insrc/result/async-result.ts, a wrapper aroundPromise<Result<...>>with chainable methods: constructors (ok,fail,fromResult,fromResultPromise,fromPromise), aggregations (all), transforms (map,mapFail,flatMap,mapAsync,flatMapAsync,chain), pattern matching (match,matchAsync), andtoPromise. - Implemented
AsyncResult.allwith documented short-circuit (sequential) evaluation. - Added tests covering functionality and short-circuit behavior:
src/result/async-result.spec.tsandsrc/result/async-result.all.spec.ts. - Exported
AsyncResultviasrc/result/public_api.ts.
| static all<T, E>(items: ReadonlyArray<AsyncResult<T, E>>): AsyncResult<ReadonlyArray<T>, E> { | ||
| const p = (async () => { | ||
| const acc: T[] = [] | ||
| for (const ar of items) { | ||
| const r = await ar.toPromise() | ||
| if (r.isFail()) return Result.fail<ReadonlyArray<T>, E>(r.unwrapFail()) | ||
| acc.push(r.unwrap()) | ||
| } | ||
| return Result.ok<ReadonlyArray<T>, E>(acc) | ||
| })() | ||
| return new AsyncResult<ReadonlyArray<T>, E>(p) | ||
| } |
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all short-circuits correctly, but if any inner AsyncResult unexpectedly rejects (e.g., via a flawed producer or fromResultPromise), this method will reject and violate the non-throwing invariant. Consider hardening with a try/catch around await ar.toPromise() to convert unexpected rejections to a Fail.
Suggestion
Wrap the per-item await in a try/catch so AsyncResult.all never rejects:
static all<T, E>(items: ReadonlyArray<AsyncResult<T, E>>): AsyncResult<ReadonlyArray<T>, E> {
const p = (async (): Promise<IResult<ReadonlyArray<T>, E>> => {
const acc: T[] = []
for (const ar of items) {
let r: IResult<T, E>
try {
r = await ar.toPromise()
} catch (e) {
return Result.fail<ReadonlyArray<T>, E>(e as E)
}
if (r.isFail()) return Result.fail<ReadonlyArray<T>, E>(r.unwrapFail())
acc.push(r.unwrap())
}
return Result.ok<ReadonlyArray<T>, E>(acc)
})()
return new AsyncResult<ReadonlyArray<T>, E>(p)
}Reply with "@CharlieHelps yes please" if you’d like me to push this hardening.
| matchAsync<M>(pattern: { ok: (val: TOk) => Promise<M>; fail: (err: TFail) => Promise<M> }): Promise<M> { | ||
| return this.promise.then(r => (r.isOk() ? pattern.ok(r.unwrap()) : pattern.fail(r.unwrapFail()))) | ||
| } |
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matchAsync forces both handlers to be async (Promise<M>), which is ergonomically restrictive. Allowing M | Promise<M> for handlers and lifting via Promise.resolve enables mixing sync/async branches without ceremony and aligns with typical match APIs.
Suggestion
Broaden handler types and lift results through Promise.resolve:
matchAsync<M>(pattern: { ok: (val: TOk) => M | Promise<M>; fail: (err: TFail) => M | Promise<M> }): Promise[M] {
return this.promise.then((r) => Promise.resolve(
r.isOk() ? pattern.ok(r.unwrap()) : pattern.fail(r.unwrapFail())
))
}Reply with "@CharlieHelps yes please" if you’d like me to implement this ergonomic improvement.
| mapAsync<M>(fn: (val: TOk) => Promise<M>): AsyncResult<M, TFail> { | ||
| const p = this.promise.then(r => r.flatMapPromise(fn)) | ||
| return new AsyncResult<M, TFail>(p) | ||
| } | ||
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| flatMapAsync<M>(fn: (val: TOk) => Promise<IResult<M, TFail>>): AsyncResult<M, TFail> { | ||
| const p = this.promise.then(async r => { | ||
| if (r.isOk()) { | ||
| try { | ||
| const next = await fn(r.unwrap()) | ||
| return next | ||
| } catch (e) { | ||
| return Result.fail<M, TFail>(e as TFail) | ||
| } | ||
| } | ||
| return Result.fail<M, TFail>(r.unwrapFail()) | ||
| }) | ||
| return new AsyncResult<M, TFail>(p) | ||
| } |
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mapAsync delegates to r.flatMapPromise(fn) while flatMapAsync implements its own try/catch. Mixed patterns increase cognitive load and risk subtle differences in error handling. Unify the approach so both APIs handle thrown/rejected errors consistently.
Suggestion
Implement mapAsync in terms of flatMapAsync to keep a single error‑handling strategy:
mapAsync<M>(fn: (val: TOk) => Promise<M>): AsyncResult<M, TFail> {
return this.flatMapAsync(async (v) => {
try {
return Result.ok<M, TFail>(await fn(v))
} catch (e) {
return Result.fail<M, TFail>(e as TFail)
}
})
}Alternatively, extract a private helper to normalize async mapping in one place.
Reply with "@CharlieHelps yes please" if you'd like me to add a commit with this refactor.
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@CharlieHelps yes please
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Expand this to see my work.
- Read and acknowledged the inline reply in
src/result/async-result.ts(reply by @patrickmichalina: “yes please”) regarding theAsyncResultaddition. - Verified
AsyncResult.fromPromisedelegates toResult.fromPromiseviareturn new AsyncResult<TOk, TFail>(Result.fromPromise<TOk, TFail>(promise))insrc/result/async-result.ts:35–36. - Confirmed
mapAsyncusesr.flatMapPromise(fn)to liftPromise<M>intoResult<M, TFail>while preserving failure propagation (src/result/async-result.ts:74–76). - Confirmed
flatMapAsyncaccepts(val) => Promise<IResult<M, TFail>>and preserves short‑circuiting without double wrapping (src/result/async-result.ts:79–106). - Cross-checked
Result.flatMapPromisebehavior for Ok and Fail variants to ensure parity: Ok wraps resolve toResult.okand rejects toResult.fail(src/result/result.ts:1522–1550), Fail short‑circuits returningResult.fail(src/result/result.ts:1896–1906,1928–1951). - Noted tests in
src/result/async-result.spec.tscover “flatMapAsync should flatten Promise<Result<...>>” andfromPromisesuccess/failure cases, matching intended semantics.
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Implemented the “unify mapAsync” change.
AsyncResult.mapAsyncnow delegates toflatMapAsyncso async error handling is centralized and consistent.- No API or behavior changes beyond the refactor.
Commit: aad4a9b (“refactor(result): unify AsyncResult.mapAsync via flatMapAsync for consistent error handling”)
Diff (key part)
// src/result/async-result.ts
mapAsync<M>(fn: (val: TOk) => Promise<M>): AsyncResult<M, TFail> {
// Delegate to flatMapAsync so async error handling is centralized.
return this.flatMapAsync(async (v) => Result.ok<M, TFail>(await fn(v)))
}Verification
# Jest: 30/30 suites passed; 330 tests passed; 100% coverage
$ npm test
# TypeScript: no errors; ESLint: 0 errors
$ npm run lintRe-requested review from @CharlieHelps.
| // Should return well before the slow item resolves (200ms). Allow a generous margin. | ||
| expect(elapsed).toBeLessThan(150) | ||
| }) |
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The timing-based assertion in this test is brittle and can be flaky in slower CI environments. Instead of measuring elapsed milliseconds, assert that the slow branch wasn’t observed (e.g., via a side-effect flag) when the early failure short-circuits.
Suggestion
Rewrite the test to avoid time-based thresholds by asserting the slow path didn’t run:
it('should short-circuit and not wait for later items after a failure', async () => {
const a = AsyncResult.ok<number, string>(1)
const bad = AsyncResult.fail<number, string>('boom')
let slowResolved = false
const slow = AsyncResult.fromPromise<number, string>(
new Promise<number>(resolve => setTimeout(() => { slowResolved = true; resolve(99) }, 200))
)
const res = await AsyncResult.all([a, bad, slow]).toPromise()
expect(res.isFail()).toBe(true)
expect(res.unwrapFail()).toBe('boom')
expect(slowResolved).toBe(false)
})Reply with "@CharlieHelps yes please" if you’d like me to update the test accordingly.
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| it('chain should convert sync throws in the callback into Fail (no rejection)', async () => { | ||
| const boom = (n: number): AsyncResult<number, string> => { | ||
| void n |
| it('chain should convert sync throws in the callback into Fail (no rejection)', async () => { | ||
| const boom = (n: number): AsyncResult<number, string> => { | ||
| void n | ||
| throw 'oops' |
| }) | ||
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| it('match and matchAsync should resolve with the proper branch', async () => { | ||
| const m1 = await AsyncResult.ok<number, string>(2).match({ ok: n => n * 2, fail: (e) => { void e; return -1 } }) |
| const m1 = await AsyncResult.ok<number, string>(2).match({ ok: n => n * 2, fail: (e) => { void e; return -1 } }) | ||
| expect(m1).toBe(4) | ||
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| const m2 = await AsyncResult.ok<number, string>(3).matchAsync({ ok: async n => n * 3, fail: async (e) => { void e; return -1 } }) |
| const m2 = await AsyncResult.ok<number, string>(3).matchAsync({ ok: async n => n * 3, fail: async (e) => { void e; return -1 } }) | ||
| expect(m2).toBe(9) | ||
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| const m3 = await AsyncResult.fail<number, string>('x').matchAsync({ ok: async (n) => { void n; return 0 }, fail: async e => e.length }) |
…sistent error handling
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fromResultusesinstanceof Promiseand does not guard against rejections; normalize withPromise.resolveand convert unexpected rejections intoFailto maintain the non-throwing invariant.fromResultPromiseandallcan leak unexpected rejections, breaking the invariant thatAsyncResultresolves to aResultand never rejects—wrap intry/catchand convert toFail.matchAsyncis unnecessarily restrictive; allow sync handlers by lifting withPromise.resolvefor better ergonomics.- Timing-based tests in
async-result.all.spec.tsandasync-result.spec.tsare brittle; prefer side-effect assertions for determinism.
Summary of changes
- Introduced
AsyncResult<TOk, TFail>as a point-free wrapper overPromise<Result<...>>with chainable methods: constructors (ok,fail,fromResult,fromResultPromise,fromPromise), transformations (map,mapFail,flatMap,mapAsync,flatMapAsync,chain), matching (match,matchAsync), aggregation (all), andtoPromise. - Implemented
AsyncResult.allwith documented sequential short-circuiting on the firstFail. - Added thorough tests in
src/result/async-result.spec.tsand a focused short-circuit test insrc/result/async-result.all.spec.ts. - Exported
AsyncResultviasrc/result/public_api.ts.
| static fromResult<TOk, TFail>(result: IResult<TOk, TFail> | Promise<IResult<TOk, TFail>>): AsyncResult<TOk, TFail> { | ||
| const p = result instanceof Promise ? result : Promise.resolve(result) | ||
| return new AsyncResult<TOk, TFail>(p) | ||
| } |
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fromResult uses instanceof Promise, which is brittle for thenables and cross‑realm promises and unnecessary. Prefer Promise.resolve to normalize both synchronous values and thenables. Additionally, to maintain the implicit invariant that AsyncResult should resolve to a Result and never reject, convert unexpected rejections into a Fail.
Suggestion
Replace the implementation with a Promise.resolve(...).catch(...) normalization:
static fromResult<TOk, TFail>(result: IResult<TOk, TFail> | Promise<IResult<TOk, TFail>>): AsyncResult<TOk, TFail> {
const p = Promise.resolve(result).catch((e) => Result.fail<TOk, TFail>(e as TFail))
return new AsyncResult<TOk, TFail>(p)
}Reply with "@CharlieHelps yes please" if you want me to add a commit with this change.
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@CharlieHelps yes please
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Expand this to see my work.
- Reviewed
src/result/async-result.spec.tsand confirmed no tests depend on raw Promise rejection passthrough; failures are asserted viaunwrapFail(). - Updated
AsyncResult.fromResultinsrc/result/async-result.tsto wrap withPromise.resolve(result)and.catch(e => Result.fail<TOk, TFail>(e as TFail)), aligning error handling withfromPromise/flatMapAsyncand the review on PR #209. - Added spec "fromResultPromise should convert a rejecting Promise into Fail (non-throwing invariant)" in
src/result/async-result.spec.ts, exercisingAsyncResult.fromResultPromiseon a rejected promise and assertingunwrapFail()returns'nope'. - Test suite passed: 30/30 suites, 332/332 tests; coverage at 100% across files, including
src/result/async-result.tsandsrc/result/async-result.spec.ts.
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Implemented the “yes please” change to normalize AsyncResult.fromResult.
- AsyncResult.fromResult now uses Promise.resolve(...).catch(...) to support thenables and cross‑realm promises and to convert unexpected rejections into Fail.
- For consistency and to preserve the non‑throwing invariant across constructors, AsyncResult.fromResultPromise now also converts rejections into Fail.
- Added focused tests to keep coverage at 100% and to exercise the new rejection paths.
Commit: 4f103c3
Changes
- src/result/async-result.ts
- fromResult: replaced instanceof check with Promise.resolve(result).catch(e => Result.fail(e)).
- fromResultPromise: added catch to convert unexpected rejections into Fail.
- src/result/async-result.spec.ts
- Added tests asserting that rejecting Promise inputs to fromResult and fromResultPromise become Fail, maintaining the non‑throwing invariant.
Verification
# Jest: 30/30 suites passed; 332 tests passed; 100% coverage
$ npm testRe‑requested review from @CharlieHelps.
| const startedAt = Date.now() | ||
| const res = await AsyncResult.all([a, b, c]).toPromise() | ||
| const elapsed = Date.now() - startedAt | ||
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| expect(res.isFail()).toBe(true) | ||
| expect(res.unwrapFail()).toBe('boom') | ||
| // Should finish well before the third completes (1000ms) | ||
| expect(elapsed).toBeLessThan(500) | ||
| // And third should not be marked completed yet at the moment of resolution | ||
| expect(thirdCompleted).toBe(false) |
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This test already uses a side-effect flag (thirdCompleted) to prove short-circuiting, but still relies on an elapsed-time assertion. The timing check is unnecessary and can flake on slower runners. Drop the elapsed-time assertion and keep the flag-based assertion for determinism.
Suggestion
Remove the elapsed-time measurement and assertion, keeping the side-effect check:
const res = await AsyncResult.all([a, b, c]).toPromise()
expect(res.isFail()).toBe(true)
expect(res.unwrapFail()).toBe('boom')
// And third should not be marked completed yet at the moment of resolution
expect(thirdCompleted).toBe(false)Reply with "@CharlieHelps yes please" if you’d like me to make this test less flaky.
…catch to maintain non-throwing invariant - Use Promise.resolve(...).catch(...) to support thenables/cross-realm promises and convert unexpected rejections into Fail - Harden fromResultPromise to convert rejections into Fail for consistency - Add tests covering rejecting inputs for fromResult and fromResultPromise to keep 100% coverage Refs: PR #209 review ("@CharlieHelps yes please" on normalization).
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Overall implementation is solid and aligns with the goal of point-free async composition. The main risks are test flakiness due to time-based assertions and minor duplication in fromResultPromise. Consider hardening all with a try/catch to guard against future regressions that could cause unexpected rejections. matchAsync can be made more ergonomic by accepting sync handlers via Promise.resolve lifting.
Additional notes (1)
- Maintainability |
src/result/async-result.spec.ts:180-190
Requested in the PR discussion: add coverage to demonstrate usage withoutasync/await, and verify lazy invocation (handlers aren’t executed when short-circuited). Adding these tests will document ergonomics and guard against regressions in short-circuit behavior.
Summary of changes
- Introduced
AsyncResult<TOk, TFail>insrc/result/async-result.ts, a wrapper overPromise<Result<...>>with chainable APIs: constructors (ok,fail,fromResult,fromResultPromise,fromPromise), transforms (map,mapFail,flatMap,mapAsync,flatMapAsync,chain), pattern matching (match,matchAsync), aggregation (all), andtoPromise. - Implemented sequential, short-circuiting
AsyncResult.alland hardened constructors to normalize inputs and convert rejections intoFail. - Added comprehensive tests in
src/result/async-result.spec.tsand a focused short-circuit test insrc/result/async-result.all.spec.ts. - Exported
AsyncResultfromsrc/result/public_api.ts.
Implements a point-free async API for Result by introducing
AsyncResult<Ok, Fail>, a thin wrapper aroundPromise<Result<...>>so you can chain without mixing.then.Changes
AsyncResultclass with chainable methods:map,mapAsync,flatMap,flatMapAsync,chain,match,matchAsync,toPromise, andall.src/result/public_api.ts.src/result/async-result.spec.ts(100% coverage).This addresses the ergonomics issue raised in #171 (point-free async chaining).
Verification