ef285b5c97
* fix: stabilize validation and tests on Windows * test: add Windows smoke coverage for skill activation * refactor: make setup_web script CommonJS * fix: repair aegisops-ai frontmatter * docs: add when-to-use guidance to core skills * docs: add when-to-use guidance to Apify skills * docs: add when-to-use guidance to Google and Expo skills * docs: add when-to-use guidance to Makepad skills * docs: add when-to-use guidance to git workflow skills * docs: add when-to-use guidance to fp-ts skills * docs: add when-to-use guidance to Three.js skills * docs: add when-to-use guidance to n8n skills * docs: add when-to-use guidance to health analysis skills * docs: add when-to-use guidance to writing and review skills * meta: sync generated catalog metadata * docs: add when-to-use guidance to Robius skills * docs: add when-to-use guidance to review and workflow skills * docs: add when-to-use guidance to science and data skills * docs: add when-to-use guidance to tooling and automation skills * docs: add when-to-use guidance to remaining skills * fix: gate bundle helper execution in Windows activation * chore: drop generated artifacts from contributor PR * docs(maintenance): Record PR 457 sweep Document the open issue triage, PR supersedence decision, local verification, and source-only cleanup that prepared PR #457 for re-running CI. --------- Co-authored-by: sickn33 <sickn33@users.noreply.github.com>
112 lines
2.6 KiB
Markdown
112 lines
2.6 KiB
Markdown
---
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name: fp-taskeither-ref
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description: Quick reference for TaskEither. Use when user needs async error handling, API calls, or Promise-based operations that can fail.
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risk: unknown
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source: community
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version: 1.0.0
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tags: [fp-ts, taskeither, async, promise, error-handling, quick-reference]
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---
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# TaskEither Quick Reference
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TaskEither = async operation that can fail. Like `Promise<Either<E, A>>`.
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## When to Use
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- You need a quick fp-ts reference for async operations that can fail.
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- The task involves API calls, Promise wrapping, or composing asynchronous error-handling pipelines.
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- You want a concise cheat sheet for `TaskEither` operators and patterns.
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## Create
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```typescript
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import * as TE from 'fp-ts/TaskEither'
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TE.right(value) // Async success
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TE.left(error) // Async failure
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TE.tryCatch(asyncFn, toError) // Promise → TaskEither
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TE.fromEither(either) // Either → TaskEither
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```
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## Transform
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```typescript
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TE.map(fn) // Transform success value
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TE.mapLeft(fn) // Transform error
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TE.flatMap(fn) // Chain (fn returns TaskEither)
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TE.orElse(fn) // Recover from error
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```
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## Execute
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```typescript
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// TaskEither is lazy - must call () to run
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const result = await myTaskEither() // Either<E, A>
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// Or pattern match
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await pipe(
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myTaskEither,
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TE.match(
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(err) => console.error(err),
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(val) => console.log(val)
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)
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)()
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```
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## Common Patterns
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```typescript
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import { pipe } from 'fp-ts/function'
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import * as TE from 'fp-ts/TaskEither'
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// Wrap fetch
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const fetchUser = (id: string) => TE.tryCatch(
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() => fetch(`/api/users/${id}`).then(r => r.json()),
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(e) => ({ type: 'NETWORK_ERROR', message: String(e) })
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)
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// Chain async calls
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pipe(
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fetchUser('123'),
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TE.flatMap(user => fetchPosts(user.id)),
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TE.map(posts => posts.length)
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)
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// Parallel calls
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import { sequenceT } from 'fp-ts/Apply'
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sequenceT(TE.ApplyPar)(
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fetchUser('1'),
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fetchPosts('1'),
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fetchComments('1')
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)
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// With recovery
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pipe(
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fetchUser('123'),
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TE.orElse(() => TE.right(defaultUser)),
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TE.getOrElse(() => defaultUser)
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)
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```
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## vs async/await
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```typescript
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// ❌ async/await - errors hidden
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async function getUser(id: string) {
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try {
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const res = await fetch(`/api/users/${id}`)
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return await res.json()
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} catch (e) {
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return null // Error info lost
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}
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}
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// ✅ TaskEither - errors typed and composable
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const getUser = (id: string) => pipe(
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TE.tryCatch(() => fetch(`/api/users/${id}`), toNetworkError),
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TE.flatMap(res => TE.tryCatch(() => res.json(), toParseError))
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)
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```
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Use TaskEither when you need **typed errors** for async operations.
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