Preserve @Bindable's binding identity (#56)

SwiftUI's vanilla `@Bindable` seems to preserve the underlying identity of its derived bindings, so we should do the same by holding onto a private binding over time under the hood. Fixes #55.
pointfreeco · Apr 4, 2024 · 520c458 · 520c458
1 parent 83fc3d8
commit 520c458
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Showing 4 changed files with 55 additions and 15 deletions.
diff --git a/Sources/Perception/Bindable.swift b/Sources/Perception/Bindable.swift
@@ -13,8 +13,13 @@
   @dynamicMemberLookup
   @propertyWrapper
   public struct Bindable<Value> {
+    private let binding: UncheckedSendable<Binding<Value>>
+
     /// The wrapped object.
-    public var wrappedValue: Value
+    public var wrappedValue: Value {
+      get { self.binding.value.wrappedValue }
+      set { self.binding.value.wrappedValue = newValue }
+    }
 
     /// The bindable wrapper for the object that creates bindings to its properties using dynamic
     /// member lookup.
@@ -26,20 +31,23 @@
     public subscript<Subject>(
       dynamicMember keyPath: ReferenceWritableKeyPath<Value, Subject>
     ) -> Binding<Subject> where Value: AnyObject {
-      Binding(
-        get: { self.wrappedValue[keyPath: keyPath] },
-        set: { self.wrappedValue[keyPath: keyPath] = $0 }
-      )
+      self.binding.value[dynamicMember: keyPath]
     }
 
     /// Creates a bindable object from an observable object.
     public init(wrappedValue: Value) where Value: AnyObject & Perceptible {
-      self.wrappedValue = wrappedValue
+      var value = wrappedValue
+      self.binding = UncheckedSendable(
+        Binding(
+          get: { value },
+          set: { value = $0 }
+        )
+      )
     }
 
     /// Creates a bindable object from an observable object.
     public init(_ wrappedValue: Value) where Value: AnyObject & Perceptible {
-      self.wrappedValue = wrappedValue
+      self.init(wrappedValue: wrappedValue)
     }
 
     /// Creates a bindable from the value of another bindable.

diff --git a/Sources/Perception/Internal/UncheckedSendable.swift b/Sources/Perception/Internal/UncheckedSendable.swift
@@ -0,0 +1,6 @@
+struct UncheckedSendable<Value>: @unchecked Sendable {
+  let value: Value
+  init(_ value: Value) {
+    self.value = value
+  }
+}
diff --git a/Sources/Perception/WithPerceptionTracking.swift b/Sources/Perception/WithPerceptionTracking.swift
@@ -164,10 +164,3 @@ public enum _PerceptionLocals {
   @TaskLocal public static var isInPerceptionTracking = false
   @TaskLocal public static var skipPerceptionChecking = false
 }
-
-private struct UncheckedSendable<A>: @unchecked Sendable {
-  let value: A
-  init(_ value: A) {
-    self.value = value
-  }
-}
diff --git a/Tests/PerceptionTests/RuntimeWarningTests.swift b/Tests/PerceptionTests/RuntimeWarningTests.swift
@@ -5,21 +5,23 @@
   import XCTest
 
   @available(iOS 16, macOS 13, tvOS 16, watchOS 9, *)
-  @MainActor
   final class RuntimeWarningTests: XCTestCase {
+    @MainActor
     func testNotInPerceptionBody() {
       let model = Model()
       model.count += 1
       XCTAssertEqual(model.count, 1)
     }
 
+    @MainActor
     func testInPerceptionBody_NotInSwiftUIBody() {
       let model = Model()
       _PerceptionLocals.$isInPerceptionTracking.withValue(true) {
         _ = model.count
       }
     }
 
+    @MainActor
     func testNotInPerceptionBody_InSwiftUIBody() {
       struct FeatureView: View {
         let model = Model()
@@ -30,6 +32,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testNotInPerceptionBody_InSwiftUIBody_Wrapper() {
       struct FeatureView: View {
         let model = Model()
@@ -42,6 +45,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testInPerceptionBody_InSwiftUIBody_Wrapper() {
       struct FeatureView: View {
         let model = Model()
@@ -56,6 +60,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testInPerceptionBody_InSwiftUIBody() {
       struct FeatureView: View {
         let model = Model()
@@ -68,6 +73,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testNotInPerceptionBody_SwiftUIBinding() {
       struct FeatureView: View {
         @State var model = Model()
@@ -80,6 +86,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testInPerceptionBody_SwiftUIBinding() {
       struct FeatureView: View {
         @State var model = Model()
@@ -92,6 +99,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testNotInPerceptionBody_ForEach() {
       struct FeatureView: View {
         @State var model = Model(
@@ -111,6 +119,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testInnerInPerceptionBody_ForEach() {
       struct FeatureView: View {
         @State var model = Model(
@@ -132,6 +141,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testOuterInPerceptionBody_ForEach() {
       struct FeatureView: View {
         @State var model = Model(
@@ -153,6 +163,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testOuterAndInnerInPerceptionBody_ForEach() {
       struct FeatureView: View {
         @State var model = Model(
@@ -176,6 +187,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testNotInPerceptionBody_Sheet() {
       struct FeatureView: View {
         @State var model = Model(child: Model())
@@ -190,6 +202,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testInnerInPerceptionBody_Sheet() {
       struct FeatureView: View {
         @State var model = Model(child: Model())
@@ -206,6 +219,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testOuterInPerceptionBody_Sheet() {
       struct FeatureView: View {
         @State var model = Model(child: Model())
@@ -222,6 +236,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testOuterAndInnerInPerceptionBody_Sheet() {
       struct FeatureView: View {
         @State var model = Model(child: Model())
@@ -240,6 +255,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testActionClosure() {
       struct FeatureView: View {
         @State var model = Model()
@@ -252,6 +268,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testActionClosure_CallMethodWithArguments() {
       struct FeatureView: View {
         @State var model = Model()
@@ -268,6 +285,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testActionClosure_WithArguments() {
       struct FeatureView: View {
         @State var model = Model()
@@ -282,6 +300,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testActionClosure_WithArguments_ImplicitClosure() {
       struct FeatureView: View {
         @State var model = Model()
@@ -297,6 +316,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testImplicitActionClosure() {
       struct FeatureView: View {
         @State var model = Model()
@@ -312,6 +332,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testRegistrarDisablePerceptionTracking() {
       struct FeatureView: View {
         let model = Model()
@@ -324,6 +345,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testGlobalDisablePerceptionTracking() {
       let previous = Perception.isPerceptionCheckingEnabled
       Perception.isPerceptionCheckingEnabled = false
@@ -338,6 +360,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testParentAccessingChildState_ParentNotObserving_ChildObserving() {
       struct ChildView: View {
         let model: Model
@@ -367,6 +390,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testParentAccessingChildState_ParentObserving_ChildNotObserving() {
       struct ChildView: View {
         let model: Model
@@ -394,6 +418,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testParentAccessingChildState_ParentNotObserving_ChildNotObserving() {
       struct ChildView: View {
         let model: Model
@@ -421,6 +446,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testParentAccessingChildState_ParentObserving_ChildObserving() {
       struct ChildView: View {
         let model: Model
@@ -450,6 +476,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testAccessInOnAppearWithAsyncTask() async throws {
       @MainActor
       struct FeatureView: View {
@@ -465,6 +492,7 @@
       try await Task.sleep(for: .milliseconds(100))
     }
 
+    @MainActor
     func testAccessInOnAppearWithAsyncTask_Implicit() async throws {
       @MainActor
       struct FeatureView: View {
@@ -484,6 +512,7 @@
       try await Task.sleep(for: .milliseconds(100))
     }
 
+    @MainActor
     func testAccessInTask() async throws {
       @MainActor
       struct FeatureView: View {
@@ -499,6 +528,7 @@
       try await Task.sleep(for: .milliseconds(100))
     }
 
+    @MainActor
     func testGeometryReader_WithoutPerceptionTracking() {
       struct FeatureView: View {
         let model = Model()
@@ -513,6 +543,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testGeometryReader_WithProperPerceptionTracking() {
       struct FeatureView: View {
         let model = Model()
@@ -527,6 +558,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     func testGeometryReader_ComputedProperty_ImproperPerceptionTracking() {
       struct FeatureView: View {
         let model = Model()
@@ -544,6 +576,7 @@
       self.render(FeatureView())
     }
 
+    @MainActor
     private func render(_ view: some View) {
       let image = ImageRenderer(content: view).cgImage
       _ = image