Swift

Swift Project Rules

Agent Automation Commands

CRITICAL: Execute these commands after EVERY implementation (see AGENT_AUTOMATION module for full workflow).

# Complete quality check sequence:
swiftlint                  # Linting
swift build                # Build verification
swift test                 # All tests (100% pass)
swift test --enable-code-coverage  # Coverage

# Security audit:
# (Use dependency scanning tools as needed)

Swift Configuration

CRITICAL: Use Swift 5.10+ with strict concurrency checking.

• Version: Swift 5.10+
• Platform: iOS 17+, macOS 14+
• Concurrency: Enabled
• Warnings as Errors: true

Package.swift Requirements

// swift-tools-version: 5.10
import PackageDescription

let package = Package(
    name: "YourPackage",
    platforms: [
        .iOS(.v17),
        .macOS(.v14),
        .watchOS(.v10),
        .tvOS(.v17)
    ],
    products: [
        .library(
            name: "YourPackage",
            targets: ["YourPackage"]
        ),
    ],
    dependencies: [],
    targets: [
        .target(
            name: "YourPackage",
            dependencies: [],
            swiftSettings: [
                .enableUpcomingFeature("StrictConcurrency"),
                .enableUpcomingFeature("BareSlashRegexLiterals"),
                .enableExperimentalFeature("StrictConcurrency=complete")
            ]
        ),
        .testTarget(
            name: "YourPackageTests",
            dependencies: ["YourPackage"]
        ),
    ]
)

Code Quality Standards

Mandatory Quality Checks

CRITICAL: After implementing ANY feature, you MUST run these commands in order.

IMPORTANT: These commands MUST match your GitHub Actions workflows to prevent CI/CD failures!

# Pre-Commit Checklist (MUST match .github/workflows/*.yml)

# 1. Format check (matches workflow - use lint mode, not --in-place!)
swift-format lint --recursive Sources Tests

# 2. Lint (matches workflow)
swiftlint lint --strict

# 3. Build (MUST pass with no warnings - matches workflow)
swift build -Xswiftc -warnings-as-errors

# 4. Run all tests (MUST pass 100% - matches workflow)
swift test --enable-code-coverage

# 5. Generate documentation (matches workflow)
swift package generate-documentation

# If ANY fails: ❌ DO NOT COMMIT - Fix first!

If ANY of these fail, you MUST fix the issues before committing.

Why This Matters:

• CI/CD failures happen when local commands differ from workflows
• Example: Using swift-format --in-place locally but lint in CI = failure
• Example: Missing --enable-code-coverage = CI coverage failures

Code Style

Use SwiftLint for code style. Configuration in .swiftlint.yml:

disabled_rules:
  - trailing_whitespace

opt_in_rules:
  - empty_count
  - explicit_init
  - first_where
  - closure_spacing
  - overridden_super_call
  - redundant_nil_coalescing
  - private_outlet
  - nimble_operator
  - attributes
  - operator_usage_whitespace
  - closure_end_indentation
  - literal_expression_end_indentation

included:
  - Sources
  - Tests

excluded:
  - .build
  - .swiftpm
  - DerivedData

line_length:
  warning: 120
  error: 140
  ignores_comments: true

type_body_length:
  warning: 300
  error: 400

file_length:
  warning: 500
  error: 800

function_body_length:
  warning: 40
  error: 60

identifier_name:
  min_length:
    warning: 2
  max_length:
    warning: 50
    error: 60

custom_rules:
  no_hardcoded_strings:
    name: "No Hardcoded Strings"
    regex: '(print|NSLog)\("'
    message: "Use localized strings instead of hardcoded strings"
    severity: warning

Testing

• Framework: XCTest (built-in)
• Location: Tests/ directory
• Async: Use async/await in tests
• Coverage: xcodebuild or swift-testing

Example test:

import XCTest
@testable import YourPackage

final class YourPackageTests: XCTestCase {
    func testProcessValidInput() async throws {
        let processor = DataProcessor()
        let result = try await processor.process("hello")
        
        XCTAssertEqual(result, "HELLO")
    }
    
    func testProcessEmptyInputThrowsError() async {
        let processor = DataProcessor()
        
        await XCTAssertThrowsError(try await processor.process("")) { error in
            XCTAssertEqual(error as? ProcessorError, .emptyInput)
        }
    }
    
    func testPerformanceExample() {
        let processor = DataProcessor()
        
        measure {
            _ = try? processor.processSync("test")
        }
    }
}

// Helper extension for async testing
extension XCTestCase {
    func XCTAssertThrowsError<T>(
        _ expression: @autoclosure () async throws -> T,
        _ errorHandler: (Error) -> Void
    ) async {
        do {
            _ = try await expression()
            XCTFail("Should have thrown an error")
        } catch {
            errorHandler(error)
        }
    }
}

Documentation

• Use Swift DocC for documentation
• Document all public APIs with ///
• Include examples and parameters

Example:

/// A processor that transforms input data.
///
/// Use this class to process strings and perform transformations.
/// The processor supports both synchronous and asynchronous operations.
///
/// ## Usage
///
/// ```swift
/// let processor = DataProcessor()
/// let result = try await processor.process("hello")
/// print(result) // Prints: HELLO
/// ```
public final class DataProcessor: Sendable {
    
    /// Creates a new data processor.
    public init() {}
    
    /// Processes the input string asynchronously.
    ///
    /// This method transforms the input by converting it to uppercase.
    ///
    /// - Parameter input: The string to process. Must not be empty.
    /// - Returns: The processed string in uppercase.
    /// - Throws: `ProcessorError.emptyInput` if the input is empty.
    ///
    /// ## Example
    ///
    /// ```swift
    /// let processor = DataProcessor()
    /// let result = try await processor.process("hello")
    /// // result is "HELLO"
    /// ```
    public func process(_ input: String) async throws -> String {
        guard !input.isEmpty else {
            throw ProcessorError.emptyInput
        }
        
        return input.uppercased()
    }
}

/// Errors that can occur during processing.
public enum ProcessorError: Error, Sendable {
    /// The input string was empty.
    case emptyInput
    /// An invalid format was encountered.
    case invalidFormat(String)
}

Concurrency

• Use async/await for asynchronous code
• Mark types as Sendable when thread-safe
• Use actors for state synchronization
• Enable strict concurrency checking

Example:

/// An actor that manages user data safely across concurrent access.
public actor UserManager {
    private var users: [String: User] = [:]
    
    /// Adds or updates a user.
    public func setUser(_ user: User, for id: String) {
        users[id] = user
    }
    
    /// Retrieves a user by ID.
    public func getUser(for id: String) -> User? {
        users[id]
    }
}

/// A thread-safe data structure.
public struct User: Sendable {
    public let id: String
    public let name: String
    public let email: String
    
    public init(id: String, name: String, email: String) {
        self.id = id
        self.name = name
        self.email = email
    }
}

/// Example of using actors with async/await
public final class UserService: Sendable {
    private let manager = UserManager()
    
    public init() {}
    
    public func fetchUser(id: String) async -> User? {
        // Actor-isolated access
        await manager.getUser(for: id)
    }
    
    public func saveUser(_ user: User) async {
        await manager.setUser(user, for: user.id)
    }
}

Project Structure

project/
├── Package.swift           # Swift Package Manager manifest
├── .swiftlint.yml          # SwiftLint configuration
├── .swift-format           # SwiftFormat configuration
├── README.md               # Project overview (allowed in root)
├── CHANGELOG.md            # Version history (allowed in root)
├── LICENSE                 # Project license (allowed in root)
├── Sources/
│   └── YourPackage/
│       ├── YourPackage.swift
│       └── ...
├── Tests/
│   └── YourPackageTests/
│       └── YourPackageTests.swift
└── docs/                   # Project documentation

Error Handling

• Use Swift's native error handling
• Create custom error types conforming to Error
• Use Result type for functions that don't throw
• Implement LocalizedError for user-facing errors

Example:

public enum NetworkError: Error {
    case invalidURL
    case noData
    case decodingFailed(Error)
    case httpError(statusCode: Int)
}

extension NetworkError: LocalizedError {
    public var errorDescription: String? {
        switch self {
        case .invalidURL:
            return "The URL provided was invalid."
        case .noData:
            return "No data was received from the server."
        case .decodingFailed(let error):
            return "Failed to decode response: \(error.localizedDescription)"
        case .httpError(let statusCode):
            return "HTTP error occurred with status code: \(statusCode)"
        }
    }
}

CI/CD Requirements

Must include GitHub Actions workflows for:

1. Testing (swift-test.yml):

   • Test on macos-latest
   • Test on Swift 5.10
   • Run on iOS, macOS platforms

2. Linting (swift-lint.yml):

   • SwiftLint: swiftlint
   • SwiftFormat: swift-format lint --recursive .
   • Build with warnings as errors

Package Publication

Publishing Swift Packages

Swift packages are published via Git tags and automatically indexed by Swift Package Index.

Prerequisites:

1. Public Git repository
2. Valid Package.swift
3. Semantic version tags

Publishing Workflow:

1. Update version documentation

2. Update CHANGELOG.md

3. Run quality checks:

   swift-format --in-place --recursive Sources Tests
   swiftlint
   swift build -Xswiftc -warnings-as-errors
   swift test
   

4. Create git tag: git tag 1.0.0 && git push --tags

5. Add to Swift Package Index: https://swiftpackageindex.com/add-a-package

6. Package available via Swift Package Manager

Publishing Checklist:

• ✅ All tests passing
• ✅ SwiftLint passes
• ✅ Code formatted with swift-format
• ✅ Build succeeds with warnings as errors
• ✅ CHANGELOG.md updated
• ✅ README.md with installation instructions
• ✅ LICENSE file present
• ✅ Documentation generated with DocC
• ✅ Package.swift metadata complete
• ✅ Semantic version tag created

Package.swift Metadata:

let package = Package(
    name: "YourPackage",
    platforms: [.iOS(.v17), .macOS(.v14)],
    products: [
        .library(name: "YourPackage", targets: ["YourPackage"]),
    ],
    targets: [
        .target(name: "YourPackage"),
        .testTarget(name: "YourPackageTests", dependencies: ["YourPackage"]),
    ]
)

Usage by Consumers:

dependencies: [
    .package(url: "https://github.com/your-org/your-package.git", from: "1.0.0")
]