* 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>
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2.2 KiB
name, description, risk, source, version, tags
| name | description | risk | source | version | tags | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| fp-either-ref | Quick reference for Either type. Use when user needs error handling, validation, or operations that can fail with typed errors. | unknown | community | 1.0.0 |
|
Either Quick Reference
Either = success or failure. Right(value) or Left(error).
When to Use
- You need a quick fp-ts reference for typed synchronous error handling.
- The task involves validation, fallible operations, or converting throwing code to
Either. - You want a compact cheat sheet rather than a long tutorial.
Create
import * as E from 'fp-ts/Either'
E.right(value) // Success
E.left(error) // Failure
E.fromNullable(err)(x) // null → Left(err), else Right(x)
E.tryCatch(fn, toError) // try/catch → Either
Transform
E.map(fn) // Transform Right value
E.mapLeft(fn) // Transform Left error
E.flatMap(fn) // Chain (fn returns Either)
E.filterOrElse(pred, toErr) // Right → Left if pred fails
Extract
E.getOrElse(err => default) // Get Right or default
E.match(onLeft, onRight) // Pattern match
E.toUnion(either) // E | A (loses type info)
Common Patterns
import { pipe } from 'fp-ts/function'
import * as E from 'fp-ts/Either'
// Validation
const validateEmail = (s: string): E.Either<string, string> =>
s.includes('@') ? E.right(s) : E.left('Invalid email')
// Chain validations (stops at first error)
pipe(
E.right({ email: 'test@example.com', age: 25 }),
E.flatMap(d => pipe(validateEmail(d.email), E.map(() => d))),
E.flatMap(d => d.age >= 18 ? E.right(d) : E.left('Must be 18+'))
)
// Convert throwing code
const parseJson = (s: string) => E.tryCatch(
() => JSON.parse(s),
(e) => `Parse error: ${e}`
)
vs try/catch
// ❌ try/catch - errors not in types
try {
const data = JSON.parse(input)
process(data)
} catch (e) {
handleError(e)
}
// ✅ Either - errors explicit in types
pipe(
E.tryCatch(() => JSON.parse(input), String),
E.map(process),
E.match(handleError, identity)
)
Use Either when error type matters and you want to chain operations.