warn on default access

Author: lukeredpath

Sources/ComposableArchitecture/SharedState/PersistenceKey/DefaultProvidingKey.swift

@@ -12,22 +12,40 @@
     ///
     /// - Parameter key: A string key identifying a value to share in memory.
     /// - Returns: An in-memory persistence key.
-      public static func inMemory<Value>(_ key: String, defaultValue: Value) -> Self
+    public static func inMemory<Value>(
+      _ key: String,
+      defaultValue: Value,
+      warnOnDefaultValueAccess: Bool = false
+    ) -> Self
     where Self == DefaultProvidingKey<InMemoryKey<Value>> {
-      DefaultProvidingKey(.init(key), defaultValue: defaultValue)
+      DefaultProvidingKey(
+        .init(key),
+        defaultValue: defaultValue,
+        warnOnDefaultValueAccess: warnOnDefaultValueAccess
+      )
     }
   }
 
   /// A decorator around an in-memory persistence strategy that provides a built-in default value.
   ///
   /// See ``PersistenceKey/inMemory(_:)`` to create values of this type.
-public struct DefaultProvidingKey<UnderlyingKey: PersistenceKey>: Hashable, PersistenceKey, Sendable
-  where UnderlyingKey: Hashable & Sendable, UnderlyingKey.Value: Hashable & Sendable {
+  public struct DefaultProvidingKey<UnderlyingKey: PersistenceKey>: Hashable, PersistenceKey, Sendable
+    where UnderlyingKey: Hashable & Sendable, UnderlyingKey.Value: Hashable & Sendable {
     let key: UnderlyingKey
-    let defaultValue: UnderlyingKey.Value
-    init(_ key: UnderlyingKey, defaultValue: UnderlyingKey.Value) {
+    let _defaultValue: UnderlyingKey.Value
+    let warnOnDefaultValueAccess: Bool
+    var defaultValue: UnderlyingKey.Value {
+      get {
+        if warnOnDefaultValueAccess {
+          runtimeWarn("Accessed default value for shared state using key: \(key)")
+        }
+        return _defaultValue
+      }
+    }
+    init(_ key: UnderlyingKey, defaultValue: UnderlyingKey.Value, warnOnDefaultValueAccess: Bool) {
       self.key = key
-      self.defaultValue = defaultValue
+      self._defaultValue = defaultValue
+      self.warnOnDefaultValueAccess = warnOnDefaultValueAccess
     }
     public func load(initialValue: UnderlyingKey.Value?) -> UnderlyingKey.Value? {
       self.key.load(initialValue: initialValue)