# Swift Error Handling Pro

> Reviews Swift error handling for modern patterns including typed throws, Result vs throws, LocalizedError conformance, and async error propagation. Use when writing or reviewing Swift error types and throwing functions.

- **Type:** Skill
- **Install:** `agentstack add skill-kelvinkosbab-appbootstrapai-swift-error-handling-pro`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [kelvinkosbab](https://agentstack.voostack.com/s/kelvinkosbab)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [kelvinkosbab](https://github.com/kelvinkosbab)
- **Source:** https://github.com/kelvinkosbab/AppBootstrapAI/tree/main/.claude/skills/swift-error-handling-pro

## Install

```sh
agentstack add skill-kelvinkosbab-appbootstrapai-swift-error-handling-pro
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

Review Swift error handling for correctness, modern API usage, and clear error semantics. Report only genuine problems - do not nitpick or invent issues.

Review process:

1. Check error type definitions for `LocalizedError`, `Equatable`, and `Sendable` conformance using `references/error-types.md`.
1. Evaluate whether typed throws (Swift 6.0+) would clarify the API using `references/typed-throws.md`.
1. Validate Result vs throws choice for the API style using `references/result-vs-throws.md`.
1. Check async error propagation patterns using `references/async-errors.md`.
1. Flag swallowed errors (catch blocks that ignore errors silently).

If doing a partial review, load only the relevant reference files.

## Core Instructions

- Target Swift 6.0 or later — typed throws is available and should be considered for library code.
- Prefer `throws` over `Result` in modern async code — `async throws` reads more naturally than returning a `Result`.
- Error types should conform to `Sendable` so they can cross isolation boundaries safely.
- Public error types should conform to `LocalizedError` and provide `errorDescription` for user-facing strings.
- Never use `try!` or `try?` to silence errors that could meaningfully be handled or surfaced.
- Avoid `catch { }` blocks that swallow the error — at minimum, log it.
- Don't wrap errors in nested types unnecessarily — flatten error hierarchies where possible.

## Output Format

Organize findings by file. For each issue:

1. State the file and relevant line(s).
2. Name the rule being violated.
3. Show a brief before/after code fix.

Skip files with no issues. End with a prioritized summary of the most impactful changes to make first.

Example output:

### Sources/Storage/FileStoreError.swift

**Line 12: Public error type should conform to `LocalizedError` for user-facing strings.**

```swift
// Before
public enum FileStoreError: Error {
    case readFailed
    case writeFailed
}

// After
public enum FileStoreError: LocalizedError {
    case readFailed
    case writeFailed

    public var errorDescription: String? {
        switch self {
        case .readFailed: "Failed to read from disk."
        case .writeFailed: "Failed to write to disk."
        }
    }
}
```

**Line 34: Use typed throws for clearer API contract.**

```swift
// Before
public func read() throws -> Data

// After
public func read() throws(FileStoreError) -> Data
```

### Summary

1. **API clarity (high):** Public error types lack `LocalizedError` conformance, making error messages opaque to consumers.
2. **Type safety (medium):** Throwing functions could use typed throws for compile-time error documentation.

End of example.

## References

- `references/error-types.md` — Defining error enums, `LocalizedError`, `Equatable`, `Sendable` conformance.
- `references/typed-throws.md` — Swift 6.0 typed throws syntax, when to use, performance benefits, migration.
- `references/result-vs-throws.md` — When to use `Result` vs `throws`, async considerations, callback APIs.
- `references/async-errors.md` — Error handling in `async`/`await`, propagation through `TaskGroup`, cancellation errors.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [kelvinkosbab](https://github.com/kelvinkosbab)
- **Source:** [kelvinkosbab/AppBootstrapAI](https://github.com/kelvinkosbab/AppBootstrapAI)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-kelvinkosbab-appbootstrapai-swift-error-handling-pro
- Seller: https://agentstack.voostack.com/s/kelvinkosbab
- Browse the marketplace: https://agentstack.voostack.com/browse

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