swift-concurrencylisted

Diagnose data races, convert callback-based code to async/await, implement actor isolation patterns, resolve Sendable conformance issues, and guide Swift 6 migration. Use when developers mention: (1) Swift Concurrency, async/await, actors, or tasks, (2) "use Swift Concurrency" or "modern concurrency patterns", (3) migrating to Swift 6, (4) data races or thread safety issues, (5) refactoring closures to async/await, (6) @MainActor, Sendable, or actor isolation, (7) concurrent code architecture or performance optimization, (8) concurrency-related linter warnings (SwiftLint or similar; e.g. async_without_await, Sendable/actor isolation/MainActor lint).
patrickserrano/lacquer · ★ 1 · Code & Development · score 67

Install: claude install-skill patrickserrano/lacquer

# Swift Concurrency ## Fast Path Before proposing a fix: 1. Analyze `Package.swift` or `.pbxproj` to determine Swift language mode, strict concurrency level, default isolation, and upcoming features. Do this always, not only for migration work. 2. Capture the exact diagnostic and offending symbol. 3. Determine the isolation boundary: `@MainActor`, custom actor, actor instance isolation, or `nonisolated`. 4. Confirm whether the code is UI-bound or intended to run off the main actor. For delayed retries, timers, and backoff tasks, separate the waiting from the UI mutation. The sleep often belongs off the main actor even when the final state update belongs on it. Project settings that change concurrency behavior: | Setting | SwiftPM (`Package.swift`) | Xcode (`.pbxproj`) | |---|---|---| | Language mode | `swiftLanguageVersions` or `-swift-version` (`// swift-tools-version:` is not a reliable proxy) | Swift Language Version | | Strict concurrency | `.enableExperimentalFeature("StrictConcurrency=targeted")` | `SWIFT_STRICT_CONCURRENCY` | | Default isolation | `.defaultIsolation(MainActor.self)` | `SWIFT_DEFAULT_ACTOR_ISOLATION` | | Upcoming features | `.enableUpcomingFeature("NonisolatedNonsendingByDefault")` | `SWIFT_UPCOMING_FEATURE_*` | If any of these are unknown, ask the developer to confirm them before giving migration-sensitive guidance. Do not guess. Guardrails: - Do not recommend `@MainActor` as a blanket fix. Justify why the code is truly UI-bound. - Prefer struc