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Swift Standards

Tools

Concern Tool Version Strategy
Linter SwiftLint Latest in container
Formatter swift-format Latest in container (Apple's official formatter)
Tests (SPM) swift test Ships with Swift toolchain
Tests (Xcode) xcodebuild macOS CI runners only

SwiftLint is the de facto standard linter for Swift, enforcing style and convention rules. swift-format is Apple's official code formatter. Both run on Linux inside the dev-toolchain container. For Xcode-based projects, xcodebuild test runs on macOS CI runners outside the container.

Configuration

SwiftLint

Config file: .swiftlint.yml at repository root.

Recommended .swiftlint.yml:

# .swiftlint.yml -- DevRail Swift lint configuration
# See: https://realm.github.io/SwiftLint/rule-directory.html

opt_in_rules:
  - closure_body_length
  - collection_alignment
  - contains_over_filter_count
  - discouraged_optional_boolean
  - empty_collection_literal
  - empty_count
  - empty_string
  - enum_case_associated_values_count
  - explicit_init
  - fatal_error_message
  - first_where
  - force_unwrapping
  - implicitly_unwrapped_optional
  - last_where
  - multiline_arguments
  - multiline_parameters
  - overridden_super_call
  - prefer_zero_over_explicit_init
  - redundant_nil_coalescing
  - sorted_first_last
  - toggle_bool
  - unneeded_parentheses_in_closure_argument
  - vertical_whitespace_closing_braces

excluded:
  - .build
  - Packages
  - DerivedData

line_length:
  warning: 120
  error: 200

type_body_length:
  warning: 300
  error: 500

file_length:
  warning: 500
  error: 1000

SwiftLint is invoked with --strict to treat all warnings as errors. Rules can be customized per-project; the defaults above match DevRail conventions for readability and safety.

swift-format

Config file: .swift-format (JSON) at repository root.

Recommended .swift-format:

{
  "version": 1,
  "lineLength": 120,
  "indentation": {
    "spaces": 4
  },
  "maximumBlankLines": 1,
  "respectsExistingLineBreaks": true,
  "lineBreakBeforeControlFlowKeywords": false,
  "lineBreakBeforeEachArgument": true,
  "indentConditionalCompilationBlocks": true,
  "lineBreakAroundMultilineExpressionChainComponents": true
}

swift-format is Apple's official Swift formatter. It handles all whitespace, indentation, and line-breaking decisions. Do not use both swift-format and SwiftLint's autocorrect for formatting -- swift-format is authoritative for style, SwiftLint is authoritative for lint rules.

Makefile Targets

Target Command Description
_lint swiftlint lint --strict Lint all Swift files (if *.swift files exist)
_format swift-format lint --strict -r . Check formatting (non-zero on unformatted)
_fix swift-format format -i -r . Apply formatting fixes
_test swift test Run SPM test suite (if Package.swift exists)

See DEVELOPMENT.md for the full Makefile contract and two-layer delegation pattern.

Pre-Commit Hooks

Local Hooks (< 30 seconds)

SwiftLint via pre-commit:

repos:
  - repo: https://github.com/realm/SwiftLint
    rev: 0.58.0
    hooks:
      - id: swiftlint
        args: ["lint", "--strict"]

Formatting is checked by swift-format inside the container via make format. There is no pre-commit formatting hook because Apple's swift-format does not have native pre-commit support, and using a different formatter (e.g., nicklockwood/SwiftFormat) would produce inconsistent results with the container. Run make fix locally to auto-format before committing.

CI-Only

These run via make test in CI pipelines. They are not configured as pre-commit hooks due to execution time:

  • swift test -- SPM test suite
  • xcodebuild test -- Xcode project tests (macOS runners only, outside container)

Notes

  • SwiftLint is the single linting tool. It is the most widely adopted Swift linter with extensive rule coverage. It runs on both macOS and Linux.
  • swift-format is the single formatting tool inside the container. Apple's official formatter handles all code style decisions. The pre-commit hook uses nicklockwood/SwiftFormat for broader pre-commit integration.
  • The Swift toolchain is included in the container. The full toolchain (swiftc, swift build, swift test, Swift Package Manager) is COPY'd from the swift:6.1-slim-bookworm builder stage.
  • Package.swift presence gates SPM testing. If no Package.swift file exists, swift test is skipped. Xcode-only projects must configure xcodebuild test in their CI pipeline directly.
  • xcodebuild does not run inside the container. It requires macOS and Xcode. For projects that use Xcode, configure a separate macOS CI job that runs xcodebuild test outside the container. The container handles linting and formatting only for these projects.
  • Security scanning uses trivy. There is no dedicated Swift dependency audit tool comparable to cargo-audit or npm audit. Trivy scans Package.resolved for known vulnerabilities in Swift package dependencies.
  • All tools are pre-installed in the dev-toolchain container. Do not install them on the host.
  • For cross-cutting practices (DRY, idempotency, error handling, testing, naming) and git workflow (branching, code review, conventional commits), see Coding Practices and Git Workflow.