Swift Code Reviewer

Swift/SwiftUI Code Review Skill

Multi-layer review covering Swift 6+ concurrency, SwiftUI patterns, performance, security, architecture, and project-specific standards. Reads .claude/CLAUDE.md and outputs Critical/High/Medium/Low severity findings with file:line references and before/after code examples.

When to Use This Skill

• "Review this PR"
• "Review my code" / "Review my changes" / "Review uncommitted changes"
• "Code review for [component]"
• "Audit this codebase" / "Check code quality"
• "Review against .claude/CLAUDE.md" / "Check if this follows our coding standards"
• "Architecture review" / "Performance audit" / "Security review"
• "Review this PR against the spec"
• "Did the agent miss anything from issue #123?"
• "What rules am I missing in CLAUDE.md based on this PR?"
• "Review this AI-generated PR"

Workflow

Phase 0 — Resolve Scope

Objective: Produce a canonical scope object before any analysis begins. Every later phase reads from this object — no phase fetches the changeset independently.

Mode Detection

Run these checks in order; stop at the first match:

Base branch resolution (for PR auto-detect and Local mode):

# 1. PR metadata (authoritative when a PR exists)
gh pr view --json baseRefName --jq '.baseRefName'
# 2. Remote default branch
git rev-parse --abbrev-ref origin/HEAD
# 3. Last resort
git branch -r | grep -E 'origin/(main|master)$' | head -1

If gh is unavailable or unauthenticated, announce loudly and fall back to Local:

"gh unavailable — falling back to local mode against origin/main. Run gh auth login for full PR scope detection."

Scope Object

scope = {
  modified:         Set<Path>   // first-class findings — full file, all severity levels
  deleted:          Set<Path>   // spec-adherence reasoning only — skip per-file analysis loop
  testsForModified: Set<Path>   // coverage findings → main report; other findings → Adjacent Observations
  related:          Set<Path>   // read for context only — all findings → Adjacent Observations
}

Populate modified and deleted:

# PR mode
gh pr view <n> --json files --jq '.files[] | [.path, .status] | @tsv'
# Local / Staged
git diff --name-status <base>...HEAD

• Status M, A, C → scope.modified
• Status D → scope.deleted
• Status R (rename) → new path → scope.modified; record old path so the agent avoids critiquing unchanged content as new code

Populate testsForModified: For each path in scope.modified:

1. Mirror into test tree: Features/Login/LoginViewModel.swift → Tests/Features/Login/LoginViewModelTests.swift
2. Fall back: search for *Tests.swift in the same directory
3. Add found paths (that exist on disk) to scope.testsForModified

Populate related: Added during Phase 1 as the agent reads imported files, protocol declarations, and parent views for context.

Excluded paths — filter from all sets before finalising:

• Pods/**, Carthage/**, .build/**, DerivedData/**, .swiftpm/**
• *.generated.swift, *.pb.swift, R.generated.swift
• Any patterns in a review-excluded-paths block in .claude/CLAUDE.md

Scope Banner (mandatory — first output before any findings)

Scope: PR #123 · base: main · modified: 7 · tests-for-modified: 3 · deleted: 1 · related: 12

For auto-detected PR, prepend a detection notice:

Detected open PR #123 (base: main). Run with --local to review uncommitted work instead.
Scope: PR #123 · base: main · modified: 7 · tests-for-modified: 3 · deleted: 1 · related: 12

For local mode:

Scope: local (base: main) · modified: 4 (3 pushed, 1 uncommitted) · related: 8

Scope Enforcement

These rules apply throughout Phases 1–3:

• L1 — file-level: Any file in scope.modified is reviewed in full — every line is in scope, not just changed lines.
• O1 — quarantine: Findings against files outside scope.modified (and outside coverage checks in scope.testsForModified) go into Adjacent Observations — a dedicated section at the end of the report labelled "out of scope for this PR — file separately."
• Severity rollup (Critical: N | High: N | …) counts only in-scope findings. Adjacent Observations are excluded.

Phase 1 — Context Gathering

1. Read the Spec
   • For PRs: gh pr view <num> --json title,body,closingIssuesReferences,labels
   • For linked issues: gh issue view <num> --json title,body,labels
   • For MRs: glab mr view <num> and glab issue view <num>
   • Extract:
     • Stated goal / problem being solved
     • Explicit acceptance criteria (look for checkboxes, "should", "must", "Given/When/Then")
     • Edge cases or non-goals mentioned
     • Out-of-scope items
   • If no PR/issue context is available, note this and fall back to inferring intent from the diff.
2. Try to load .claude/CLAUDE.md.
   • If missing: add a note to the report — "No project standards file found — review uses default Apple guidelines" — then continue.
3. Use scope.modified from Phase 0 as the authoritative file list. To understand what changed in each file:
   • PR mode: gh pr diff <n> -- <file>
   • Local mode: git diff <base>...HEAD -- <file>
   • If scope.modified is empty after Phase 0, stop and report the scope banner with no findings.
4. Read each file in scope.modified in full. As you encounter imported files, protocol declarations, parent views, and other dependencies, add them to scope.related — they can be read freely, but findings against them go to Adjacent Observations. Test files in scope.testsForModified are read here for coverage analysis.

Phase 2 — Analysis

For each category, load the reference file before writing findings:

0. Spec Adherence

Reference: references/spec-adherence.md

• Requirement Coverage
  • Does each acceptance criterion map to a concrete code change?
  • Are edge cases mentioned in the spec handled?
  • For files in scope.testsForModified: are tests covering the scenarios described in the spec? Coverage gaps → main report. Other issues found in those test files → Adjacent Observations.
• Scope Discipline
  • Flag changes outside the stated scope (scope creep)
  • Flag unrelated refactors bundled into the PR
• Deleted Files: For each path in scope.deleted, reason about whether its removal satisfies or violates a spec requirement. Include in the Requirement Coverage table; skip the per-file analysis loop.
• Missing Work
  • TODOs, fatalError("not implemented"), empty function bodies
  • Stubbed mocks that should be real implementations
  • Acceptance criteria with no corresponding diff
• Intent Drift
  • Code solves a similar but different problem than stated
  • Naming/structure suggests a different mental model than the spec

1. Swift Quality — concurrency, error handling, optionals, naming → references/swift-quality-checklist.md; for concurrency findings also read skills/swift-concurrency/references/sendable.md and actors.md
2. SwiftUI Patterns — property wrappers, state management, deprecated APIs → references/swiftui-review-checklist.md; for wrapper selection read skills/swiftui-expert-skill/references/state-management.md
3. Performance — view body cost, ForEach identity, lazy loading, retain cycles → references/performance-review.md
4. Security — force unwraps, Keychain vs UserDefaults, input validation, no secrets in logs → references/security-checklist.md
5. Architecture — MVVM/MVI/TCA compliance, DI, testability → references/architecture-patterns.md
6. Project Standards — validate against .claude/CLAUDE.md rules → references/custom-guidelines.md

For test file findings, consult skills/swift-testing/references/test-organization.md. For navigation/routing findings, consult skills/swiftui-ui-patterns/references/navigationstack.md.

Phase 2.5 — Pattern Detection (for Agent Loop Feedback)

Objective: Identify recurring issues that point to gaps in the agent's instructions, not just the code.

After collecting per-file findings, aggregate them:

1. Group findings by rule (e.g., "force-unwrap", "deprecated NavigationView", "missing @MainActor on UI mutation").
2. Mark any rule that fires ≥2 times across the diff as a recurring pattern.
3. For each recurring pattern, draft a one-line rule suitable for .claude/CLAUDE.md or an agent system prompt — written as a directive, not a description.
4. If the same recurring pattern appeared in past reviews (check git log of .claude/CLAUDE.md), escalate priority — the existing rule isn't strong enough or isn't being read.

Threshold rationale: one occurrence is a slip; two is a pattern; three+ means the agent's instructions are silent on this and need an explicit rule.

Reference: references/agent-loop-feedback.md.

Phase 3 — Report

Group findings by file → sort by severity within each file → write prioritized action items.

Severity: Critical (crash/data race/security hole) · High (anti-pattern/major arch violation) · Medium (quality/maintainability) · Low (style/suggestion).

Include one-sentence positive feedback where code is notably well-written. Never pad with generic praise.

Concrete Finding Examples

Force Unwrap → guard let (Critical)

LoginViewModel.swift:89 — Current:

let user = repository.currentUser!

Finding: crashes if currentUser is nil (e.g., after sign-out race condition).

Fix:

guard let user = repository.currentUser else {
    logger.error("currentUser nil — aborting login flow")
    return
}

Missing @MainActor on UI-bound ViewModel (High)

FeedViewModel.swift:12 — Current:

class FeedViewModel: ObservableObject {
    @Published var posts: [Post] = []

    func load() async {
        posts = try? await api.fetchPosts()  // ⚠️ mutates @Published off main thread
    }
}

Finding: @Published mutations must happen on the main actor in Swift 6 strict concurrency; this is a data race.

Fix:

@MainActor
@Observable
final class FeedViewModel {
    var posts: [Post] = []

    func load() async throws {
        posts = try await api.fetchPosts()  // safe: whole class is @MainActor-isolated
    }
}

Also migrate from ObservableObject/@Published to @Observable (iOS 17+) — see skills/swiftui-expert-skill/references/state-management.md.

Output Format

Scope: PR #123 · base: main · modified: 7 · tests-for-modified: 3 · deleted: 1 · related: 12

# Code Review — <scope>

## Summary
Files: N | Critical: N | High: N | Medium: N | Low: N

## Spec Adherence

**Source**: PR #123 / Issue #456

| Requirement | Status | Location |
|-------------|--------|----------|
| User can log in with email | ✅ Implemented | LoginView.swift:23 |
| Show error on invalid credentials | ⚠️ Partial — missing 401 case | LoginViewModel.swift:67 |
| Persist session in Keychain | ❌ Not implemented | — |
| Rate limit retries | ❌ Not implemented | — |

**Scope creep**: 1 unrelated change (UserSettings.swift refactor) — recommend
splitting into a separate PR.

---

## <Filename.swift>

[Severity] **<Category>** (line N)
Current: `<problematic snippet>`
Fix: <explanation + corrected snippet>

## Positive Observations
...

## Prioritized Action Items
- [Must fix] ...
- [Should fix] ...
- [Consider] ...

---

## Agent Loop Feedback

Recurring patterns suggest the following rules are missing or under-emphasized
in `.claude/CLAUDE.md`:

### Pattern: Force-unwraps (4 occurrences)
**Files**: LoginView.swift:89, NetworkService.swift:34, UserRepo.swift:12,78

**Suggested rule**:
> Never use `!`, `try!`, or `as!`. Use `guard let` with explicit early return,
> typed throws, or `as?` with handling. Force-unwraps are crashes waiting to happen.

### Pattern: Deprecated NavigationView (2 occurrences)
**Files**: ProfileView.swift:15, SettingsView.swift:22

**Suggested rule**:
> Use `NavigationStack` exclusively. `NavigationView` is deprecated as of iOS 16.

### Pattern: Business logic in View body (3 occurrences)
**Files**: LoginView.swift:45, ProfileView.swift:78, FeedView.swift:34

**Suggested rule**:
> Views must not contain business logic, network calls, or data transformations.
> Move all such work into the @Observable view model.

---

## Adjacent Observations
*Out of scope for this PR. Findings in files read for context that were not modified in this PR.
Not counted in the summary above. File separately or address in a follow-up PR.*

### <RelatedFile.swift> (unmodified)

[Severity] **<Category>** (line N)
Current: `<snippet>`
Note: <what the issue is — no action required for this PR>

Full templates and severity classification: references/feedback-templates.md.

Companion Skills

Full reference tables (all files, when to consult each): references/companion-skills.md.

Platform Commands

# GitHub PR
gh pr diff <n>
gh pr view <n> --json files,comments

# GitLab MR
glab mr diff <n>
glab mr view <n> --json

# Local changes
git diff             # unstaged
git diff --cached    # staged
git diff HEAD~1      # last commit
git diff -- path/to/file.swift

Limitations

• Spec adherence checks require an accessible PR description or linked issue. When reviewing local changes with no PR context, mark spec adherence as "not assessed" rather than guessing intent.
• Agent loop feedback assumes the code was AI-generated or AI-assisted. For fully human-written code, recurring patterns are still useful but should be framed as team coding standards rather than agent instructions.

Reference Files

• references/review-workflow.md — detailed process, diff parsing, git commands
• references/feedback-templates.md — output templates, severity classification
• references/spec-adherence.md — parsing PR/issue specs, requirement coverage tables, scope creep classification
• references/agent-loop-feedback.md — recurring-pattern threshold, directive phrasing, suggested-rule template
• references/swift-quality-checklist.md — Swift 6+, concurrency, optionals, naming
• references/swiftui-review-checklist.md — property wrappers, state, modern APIs
• references/performance-review.md — view optimization, ForEach, resource management
• references/security-checklist.md — input validation, Keychain, network security
• references/architecture-patterns.md — MVVM/MVI/TCA, DI, testability
• references/custom-guidelines.md — parsing .claude/CLAUDE.md
• references/companion-skills.md — full companion skill tables