Add rule: private_property_wrappers

[kj6dev]

Overview

Enforce private access control for SwiftUI property wrappers that represent view-internal state.

Rule Identifier

private_property_wrappers

Rationale

SwiftUI property wrappers like @State, @StateObject, and @EnvironmentObject represent view-internal state that should not be accessed directly from outside the view. Making them private enforces proper encapsulation.

Property Wrappers That Should Be Private

• @State - View's internal mutable state
• @StateObject - View owns and manages the lifecycle
• @EnvironmentObject - Injected from environment
• @Environment - Reading from environment
• @AppStorage - Persistent storage
• @SceneStorage - Scene-specific storage
• @FetchRequest - Core Data fetch
• @GestureState - Gesture tracking state
• @FocusState - Focus management
• @ScaledMetric - Dynamic type scaling

Sometimes Non-Private (configurable)

• @Binding - Often passed from parent view (public API)
• @ObservedObject - Often passed from parent

Example

// ❌ Bad
@State var counter: Int = 0

// ✅ Good
private @State var counter: Int = 0

Configuration Options

Consider strictness levels:

• Strict: All property wrappers must be private
• Moderate: Allow @binding and @ObservedObject to be non-private
• Relaxed: Only enforce for state-owning wrappers

Priority

Medium - High value, low risk, moderate effort

Reference

Full spec in docs/TODO-private-property-wrappers.md (to be archived after issue creation)