error-handling-typed-resultslisted

Enforces a typed-error spine — a hand-rolled sealed Result<T,F> plus one per-boundary sealed Failure carrying a stable code and typed params (never a localized string), returned instead of thrown; recoverable failures are values, only bugs throw. Convert-at-boundary catches narrowly with an on-clause and logs the original error+stack BEFORE returning a typed Failure; call sites switch exhaustively with no default:; the taxonomy of what the global error net (FlutterError.onError + PlatformDispatcher.onError, installed by app-startup-and-bootstrap) routes into, plus Isolate.run re-wrapping; mechanism selection (Error vs assert vs Exception vs sealed outcome) and @useResult; and a never-lose-data layer (one-transaction-per-mutation, debounced autosave drafts, optimistic soft-delete/Undo). Use when writing result.dart/failures.dart, a try/catch or sealed-switch default:, wiring bootstrap handlers, a repository/service/DAO boundary, or transactions, drafts, or soft-delete/Undo.
zakariaf/CatchLaw · ★ 0 · Data & Documents · score 55

Install: claude install-skill zakariaf/CatchLaw

# Error Handling — Typed Results Recoverable failures are typed **values** that flow through the layers and are switched on exhaustively; only genuine bugs and unrecoverable states throw, and those are caught once by a global net. Wrapped around both, never-lose-data — transactions, autosave drafts, soft-delete/Undo — is a first-class subsystem, not plumbing. Two tiers, no middle ground. Read the reference for the task at hand: - `references/result-failure-spine.md` — the `Result`/`Failure` source, the per-boundary taxonomy, convert-at-boundary, the global net, isolate re-wrapping, and local logging. - `references/mechanism-selection.md` — throw vs `assert` vs `Exception` vs sealed outcome, `@useResult`, and the runZonedGuarded decision. - `references/never-lose-data.md` — one transaction per mutation, debounced autosave drafts, optimistic soft-delete / Trash / Undo behind one filter. Run `scripts/check-swallowed-catch.sh` and `scripts/check-softdelete-parity.sh` before a PR. ## Non-negotiable rules 1. **Model recoverable failures as values, not exceptions.** Anything that fails for a runtime reason the caller must handle — DB error, file/backup I/O, notification scheduling, an expected not-found, invalid input — returns `Result<T, F extends Failure>` (sealed `Ok`/`Err`). Throwing across a layer for an *expected* failure is a review reject. 2. **Hand-roll one zero-dependency sealed `Result` and `Failure` in a Flutter-free layer** so pure logic and repositories share ONE