Make PersistenceKeyDefault load its default value lazily (#3057)

* Added autoclosure around default value for `PersistenceKeyDefault` * Added autoclosure around default value for `PersistenceKeyDefault` --------- Co-authored-by: Sean <[email protected]>
pointfreeco · May 8, 2024 · 4c36b18 · 4c36b18
1 parent c0d10e2
commit 4c36b18
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Showing 3 changed files with 31 additions and 5 deletions.
diff --git a/Sources/ComposableArchitecture/SharedState/PersistenceKey/PersistenceKeyDefault.swift b/Sources/ComposableArchitecture/SharedState/PersistenceKey/PersistenceKeyDefault.swift
@@ -24,9 +24,9 @@
 /// ```
 public struct PersistenceKeyDefault<Base: PersistenceReaderKey>: PersistenceReaderKey {
   let base: Base
-  let defaultValue: Base.Value
+  let defaultValue: () -> Base.Value
 
-  public init(_ key: Base, _ value: Base.Value) {
+  public init(_ key: Base, _ value: @autoclosure @escaping () -> Base.Value) {
     self.base = key
     self.defaultValue = value
   }
@@ -36,7 +36,7 @@ public struct PersistenceKeyDefault<Base: PersistenceReaderKey>: PersistenceRead
   }
 
   public func load(initialValue: Base.Value?) -> Base.Value? {
-    self.base.load(initialValue: initialValue ?? self.defaultValue)
+    self.base.load(initialValue: initialValue ?? self.defaultValue())
   }
 
   public func subscribe(

diff --git a/Sources/ComposableArchitecture/SharedState/References/ValueReference.swift b/Sources/ComposableArchitecture/SharedState/References/ValueReference.swift
@@ -73,7 +73,7 @@ extension Shared {
     line: UInt = #line
   ) where Key.Value == Value {
     self.init(
-      wrappedValue: persistenceKey.load(initialValue: nil) ?? persistenceKey.defaultValue,
+      wrappedValue: persistenceKey.load(initialValue: nil) ?? persistenceKey.defaultValue(),
       persistenceKey.base,
       fileID: fileID,
       line: line
@@ -159,7 +159,7 @@ extension SharedReader {
     line: UInt = #line
   ) where Key.Value == Value {
     self.init(
-      wrappedValue: persistenceKey.load(initialValue: nil) ?? persistenceKey.defaultValue,
+      wrappedValue: persistenceKey.load(initialValue: nil) ?? persistenceKey.defaultValue(),
       persistenceKey.base,
       fileID: fileID,
       line: line

diff --git a/Tests/ComposableArchitectureTests/SharedTests.swift b/Tests/ComposableArchitectureTests/SharedTests.swift
@@ -722,6 +722,28 @@ final class SharedTests: XCTestCase {
     XCTAssertEqual(isOn2, true)
     XCTAssertEqual(isOn3, true)
   }
+
+  func testSharedDefaults_Used() {
+    let didAccess = LockIsolated(false)
+    let logDefault: () -> Bool = {
+      didAccess.setValue(true)
+      return true
+    }
+    @Shared(.isActive(default: logDefault)) var isActive
+    XCTAssertEqual(isActive, true)
+    XCTAssertEqual(didAccess.value, true)
+  }
+
+  func testSharedDefaults_Unused() {
+    let didAccess = LockIsolated(false)
+    let logDefault: () -> Bool = {
+      didAccess.setValue(true)
+      return true
+    }
+    @Shared(.isActive(default: logDefault)) var isActive = false
+    XCTAssertEqual(isActive, false)
+    XCTAssertEqual(didAccess.value, false)
+  }
 
   func testSharedReaderDefaults_MultipleWithDifferentDefaults() async throws {
     @Shared(.appStorage("isOn")) var isOn = false
@@ -1035,6 +1057,10 @@ extension PersistenceReaderKey where Self == PersistenceKeyDefault<AppStorageKey
   static var isOn: Self {
     PersistenceKeyDefault(.appStorage("isOn"), false)
   }
+
+  static func isActive(default keyDefault: @escaping () -> Bool) -> Self {
+    PersistenceKeyDefault(.appStorage("isActive"), keyDefault())
+  }
 }
 
 // NB: This is a compile-time test to verify that optional shared state with defaults compiles.