swiftlint

SwiftLint (iOS / Swift)

Static analysis and style enforcement for Swift. This skill covers configuration authoring, build integration, and rollout — grounded in the realm/SwiftLint and SimplyDanny/SwiftLintPlugins docs. For a fintech codebase the goal is a lint gate that blocks new violations without a big-bang cleanup of the existing ones.

• SwiftLint has two rule engines: lint rules (syntactic, AST via SourceKit) run by swiftlint lint (default), and analyzer rules run by swiftlint analyze against a compiler log.
• Ships default-on rules plus a large opt-in set. swiftlint rules lists every rule and whether it's enabled; swiftlint reporters lists output formats.

Contents

• Install
• .swiftlint.yml
• Rule severity & thresholds
• Custom rules (regex)
• Inline suppression
• Build integration (SPM plugin / run script)
• Analyzer rules
• Reporters
• strict vs lenient
• Baselines (legacy rollout)
• CI
• Rollout strategy
• Checklist
• References: references/config-reference.md, references/custom-rules.md, references/ci-recipes.md

Install

Pin the version so every machine and CI runner lints identically — a floating SwiftLint silently changes what fails.

brew install swiftlint          # local dev (unversioned; fine for editors)
mint install realm/SwiftLint    # Mintfile-pinned

• Preferred for reproducibility: the SPM build-tool plugin (below) — it vendors a pinned binary per package, so no separate install step and no version drift between developers and CI.
• Avoid the CocoaPods SwiftLint pod on new projects; the SPM plugin supersedes it.

.swiftlint.yml

Place at the repo root (or a target/subdirectory root — SwiftLint walks up from each file and applies the nearest config). Keys:

# --- rule selection ---
disabled_rules:            # turn OFF default-on rules
  - todo
  - trailing_whitespace

opt_in_rules:              # turn ON rules that are off by default
  - empty_count
  - first_where
  - force_unwrapping
  - explicit_init
  - all                    # special: enable EVERY opt-in rule (minus disabled_rules)

# only_rules:              # allow-list: ONLY these run. Mutually exclusive with
#   - force_cast           # disabled_rules AND opt_in_rules — do not combine.
#   - force_try

analyzer_rules:            # separate list, run only by `swiftlint analyze` (all opt-in)
  - unused_import
  - unused_declaration

# --- paths (case-sensitive, relative to the config file) ---
included:                  # if set, lint ONLY these (still minus `excluded`)
  - Sources
excluded:                  # skip these; wins over `included`
  - Tests
  - .build
  - Pods
  - "**/Generated"         # generated code (protobuf, Sourcery, R.swift) — never lint

# --- output ---
reporter: "xcode"          # default; see Reporters section

# --- global severity ---
strict: false              # true → warnings become errors (nonzero exit)
lenient: false             # true → errors become warnings (never fails)