From antigravity-awesome-skills
Quick reference for TaskEither. Use when user needs async error handling, API calls, or Promise-based operations that can fail.
npx claudepluginhub absjaded/antigravity-awesome-skillsThis skill uses the workspace's default tool permissions.
TaskEither = async operation that can fail. Like `Promise<Either<E, A>>`.
Verifies tests pass on completed feature branch, presents options to merge locally, create GitHub PR, keep as-is or discard; executes choice and cleans up worktree.
Guides root cause investigation for bugs, test failures, unexpected behavior, performance issues, and build failures before proposing fixes.
Writes implementation plans from specs for multi-step tasks, mapping files and breaking into TDD bite-sized steps before coding.
TaskEither = async operation that can fail. Like Promise<Either<E, A>>.
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.