Fp taskeither ref

Skill sickn33/agentic-awesome-skills/plugins/agentic-awesome-skills-claude/skills/fp-taskeither-ref

AAS Core is the local, agent-first control plane for complete catalog discovery, agent-owned selection, stack validation, and planning, backed by 1,987+ agentic skills. Includes CLI, local MCP, catalog, plugins, and Workbench.

Install

npx -y skills add sickn33/agentic-awesome-skills --skill fp-taskeither-ref

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

What its author says it does

Copied from the file, not written here

Quick reference for TaskEither. Use when user needs async error handling, API calls, or Promise-based operations that can fail.

SKILL.md

2.9 KB, 665 tokens by cl100k_base, as published. Nobody here has run it

TaskEither Quick Reference

TaskEither = async operation that can fail. Like Promise<Either<E, A>>.

When to Use

You need a quick fp-ts reference for async operations that can fail.
The task involves API calls, Promise wrapping, or composing asynchronous error-handling pipelines.
You want a concise cheat sheet for TaskEither operators and patterns.

Create

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

Transform

TE.map(fn)               // Transform success value
TE.mapLeft(fn)           // Transform error
TE.flatMap(fn)           // Chain (fn returns TaskEither)
TE.orElse(fn)            // Recover from error

Execute

// 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)
  )
)()

Common Patterns

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)
)

vs async/await

// ❌ 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.

Limitations

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.