From antigravity-awesome-skills
Quick reference for fp-ts TaskEither, covering creation, transformation, execution, and common patterns for async error handling, API calls, and Promise-based operations.
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TaskEither = async operation that can fail. Like `Promise<Either<E, A>>`.
TaskEither = async operation that can fail. Like Promise<Either<E, A>>.
TaskEither operators and patterns.import * as TE from 'fp-ts/TaskEither'
TE.right(value) // Async success
TE.left(error) // Async failure
TE.tryCatch(asyncFn, toError) // Promise → TaskEither
TE.fromEither(either) // Either → TaskEither
TE.map(fn) // Transform success value
TE.mapLeft(fn) // Transform error
TE.flatMap(fn) // Chain (fn returns TaskEither)
TE.orElse(fn) // Recover from error
// TaskEither is lazy - must call () to run
const result = await myTaskEither() // Either<E, A>
// Or pattern match
await pipe(
myTaskEither,
TE.match(
(err) => console.error(err),
(val) => console.log(val)
)
)()
import { pipe } from 'fp-ts/function'
import * as TE from 'fp-ts/TaskEither'
// Wrap fetch
const fetchUser = (id: string) => TE.tryCatch(
() => fetch(`/api/users/${id}`).then(r => r.json()),
(e) => ({ type: 'NETWORK_ERROR', message: String(e) })
)
// Chain async calls
pipe(
fetchUser('123'),
TE.flatMap(user => fetchPosts(user.id)),
TE.map(posts => posts.length)
)
// Parallel calls
import { sequenceT } from 'fp-ts/Apply'
sequenceT(TE.ApplyPar)(
fetchUser('1'),
fetchPosts('1'),
fetchComments('1')
)
// With recovery
pipe(
fetchUser('123'),
TE.orElse(() => TE.right(defaultUser)),
TE.getOrElse(() => defaultUser)
)
// ❌ async/await - errors hidden
async function getUser(id: string) {
try {
const res = await fetch(`/api/users/${id}`)
return await res.json()
} catch (e) {
return null // Error info lost
}
}
// ✅ TaskEither - errors typed and composable
const getUser = (id: string) => pipe(
TE.tryCatch(() => fetch(`/api/users/${id}`), toNetworkError),
TE.flatMap(res => TE.tryCatch(() => res.json(), toParseError))
)
Use TaskEither when you need typed errors for async operations.
npx claudepluginhub sickn33/antigravity-awesome-skills --plugin antigravity-bundle-aas-mobile-app-builderProvides fp-ts TaskEither quick reference for creating, transforming, and executing async operations with typed errors in API calls and Promises.
Guides creation, editing, and verification of skills for AI coding agents using test-driven development with subagent scenarios. Use when authoring or debugging skills.