Provides quick fp-ts TaskEither reference for async error handling in API calls and Promise-based operations that can fail.
From antigravity-awesome-skillsnpx claudepluginhub sickn33/antigravity-awesome-skills --plugin antigravity-awesome-skillsThis skill uses the workspace's default tool permissions.
Dispatches parallel agents to independently tackle 2+ tasks like separate test failures or subsystems without shared state or dependencies.
Executes pre-written implementation plans: critically reviews, follows bite-sized steps exactly, runs verifications, tracks progress with checkpoints, uses git worktrees, stops on blockers.
Guides idea refinement into designs: explores context, asks questions one-by-one, proposes approaches, presents sections for approval, writes/review specs before coding.
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.