flutter-dart-code-review

name	flutter-dart-code-review
description	Library-agnostic Flutter/Dart code review checklist covering widget best practices, state management patterns, Dart idioms, performance, accessibility, security, and clean architecture.
origin	ECC

Flutter/Dart Code Review Best Practices

Comprehensive, library-agnostic checklist for reviewing Flutter/Dart applications.

1. General Project Health

• Project follows consistent folder structure (feature-first or layer-first)
• Proper separation of concerns: UI, business logic, data layers
• No business logic in widgets; widgets are purely presentational
• analysis_options.yaml includes a strict lint set with strict analyzer settings enabled

2. Dart Language Pitfalls

• Missing type annotations leading to dynamic -- enable strict-casts, strict-inference, strict-raw-types
• Null safety misuse: Excessive ! (bang operator) instead of proper null checks
• Catching too broadly: catch (e) without on clause
• late overuse where nullable or constructor initialization would be safer
• Prefer final for locals and const for compile-time constants
• Use package: imports for consistency

3. Widget Best Practices

• No single widget with a build() method exceeding ~80-100 lines
• const constructors used wherever possible
• Colors from Theme.of(context).colorScheme, not hardcoded values
• Text styles from Theme.of(context).textTheme
• No network calls, file I/O, or heavy computation in build()

4. State Management (Library-Agnostic)

• Business logic lives outside the widget layer
• State managers receive dependencies via injection
• Mutually exclusive states use sealed types, not boolean flags
• Every async operation models loading, success, and error as distinct states
• State consumer widgets scoped as narrow as possible
• All manual subscriptions cancelled in dispose() / close()

5. Performance

• const widgets used to stop rebuild propagation
• RepaintBoundary used around complex subtrees
• ListView.builder used instead of ListView(children: [...]) for large lists
• No sorting, filtering, or mapping large collections in build()

6. Testing

• Unit tests cover all business logic
• Widget tests cover individual widget behavior
• Integration tests cover critical user flows
• Aim for 80%+ line coverage on business logic
• External dependencies are mocked or faked

7. Accessibility

• Semantics widget used for screen reader labels
• Tappable targets at least 48x48 pixels
• Color is not the sole indicator of state
• Text scales with system font size settings

8. Security

• Sensitive data stored using platform-secure storage
• API keys NOT hardcoded in Dart source
• HTTPS enforced for all API calls
• All user input validated before sending to API

9. Navigation and Routing

• One routing approach used consistently
• Route arguments are typed -- no Map<String, dynamic> casting
• Auth guards/redirects centralized
• Deep links configured for both Android and iOS

10. Error Handling

• FlutterError.onError overridden to capture framework errors
• Error reporting service integrated
• API errors result in user-friendly error UI, not crashes
• Raw exceptions mapped to user-friendly messages before reaching the UI