Add EquatableView

Sources/OpenSwiftUI/View/EquatableView.swift

@@ -0,0 +1,115 @@
+//
+//  EquatableView.swift
+//  OpenSwiftUI
+//
+//  Audited for 6.5.4
+//  Status: Complete
+//  ID: 93C51C71D9D4CBAB391E78A2AAC640D6 (SwiftUI)
+
+import OpenGraphShims
+@_spi(ForOpenSwiftUIOnly)
+import OpenSwiftUICore
+
+// MARK: - EquatableView
+
+/// A view type that compares itself against its previous value and prevents its
+/// child updating if its new value is the same as its old value.
+@available(OpenSwiftUI_v1_0, *)
+@frozen
+public struct EquatableView<Content>: View, UnaryView, PrimitiveView where Content: Equatable, Content: View {
+    public var content: Content
+
+    @inlinable
+    public init(content: Content) {
+        self.content = content
+    }
+
+    nonisolated public static func _makeView(
+        view: _GraphValue<Self>,
+        inputs: _ViewInputs
+    ) -> _ViewOutputs {
+        let child = Child(view: view.value)
+        return Content.makeDebuggableView(
+            view: _GraphValue(child),
+            inputs: inputs
+        )
+    }
+
+    private struct Child: Rule, AsyncAttribute {
+        @Attribute var view: EquatableView
+
+        typealias Value = Content
+
+        var value: Value {
+            view.content
+        }
+
+        static var comparisonMode: ComparisonMode {
+            .equatableAlways
+        }
+    }
+}
+
+@available(*, unavailable)
+extension EquatableView: Sendable {}
+
+extension View where Self: Equatable {
+    /// Prevents the view from updating its child view when its new value is the
+    /// same as its old value.
+    @inlinable
+    nonisolated public func equatable() -> EquatableView<Self> {
+        EquatableView(content: self)
+    }
+}
+
+// MARK: - EquatableProxyView
+
+package struct EquatableProxyView<Content, Token>: View, UnaryView, PrimitiveView where Content: View, Token: Equatable {
+    package var content: Content
+
+    package var token: Token
+
+    package init(content: Content, token: Token) {
+        self.content = content
+        self.token = token
+    }
+
+    nonisolated public static func _makeView(
+        view: _GraphValue<Self>,
+        inputs: _ViewInputs
+    ) -> _ViewOutputs {
+        let child = Child(view: view.value, lastToken: nil)
+        return Content.makeDebuggableView(
+            view: _GraphValue(child),
+            inputs: inputs
+        )
+    }
+
+    private struct Child: StatefulRule, AsyncAttribute {
+        @Attribute var view: EquatableProxyView
+        var lastToken: Token?
+
+        init(view: Attribute<EquatableProxyView>, lastToken: Token?) {
+            self._view = view
+            self.lastToken = lastToken
+        }
+
+        typealias Value = Content
+
+        mutating func updateValue() {
+            guard hasValue && lastToken == view.token else {
+                value = view.content
+                lastToken = view.token
+                return
+            }
+        }
+    }
+}
+
+extension View {
+    /// Prevents the view from updating its child view when its new value is the
+    /// same as its old value.
+    nonisolated package func equatableProxy<Token>(_ token: Token) -> EquatableProxyView<Self, Token> where Token: Equatable {
+        EquatableProxyView(content: self, token: token)
+    }
+}

Sources/OpenSwiftUITestsSupport/Integration/PlatformHostingControllerHelper.swift

@@ -15,7 +15,7 @@ extension PlatformHostingController {
         let window = UIWindow(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
         window.rootViewController = self
         window.makeKeyAndVisible()
-        view.layoutSubviews()
+        view.layoutIfNeeded()
         #else
         let window = NSWindow(
             contentRect: CGRect(x: 0, y: 0, width: 100, height: 100),
@@ -25,7 +25,7 @@ extension PlatformHostingController {
         )
         window.contentViewController = self
         window.makeKeyAndOrderFront(nil)
-        view.layout()
+        view.layoutSubtreeIfNeeded()
         #endif
     }
 }

Tests/OpenSwiftUICompatibilityTests/View/EquatableViewTests.swift

@@ -0,0 +1,191 @@
+//
+//  EquatableViewTests.swift
+//  OpenSwiftUITests
+
+import Foundation
+import OpenSwiftUITestsSupport
+import Testing
+
+// MARK: - EquatableViewTests
+
+#if canImport(Darwin)
+
+struct EquatableViewTests {
+    // Inspired by https://swiftui-lab.com/equatableview/
+    // NOTES:
+    // 1. Even we implement Equatable and use EquatableView, the body will still call 2 times.
+    // Explain: For 2nd call, the value is actually equal but the implementation is not called due to Layout is not ready
+    // 2. If we implement Equatable but not use EquatableView, it still gets the same effect as EquatableView for POD types.
+    // The difference of using EquatableView is only required for non-POD types. (Change the Rule's default comparison mode from .equatableUnlessPOD to .alwaysEquatable)
+    // FIXME: 1. ?: Changing NumberView to non-POD types seems not working here
+    // FIXME: 2. the count is not accurate on Unit Test target
+
+    struct NonEquatableNumberView: View {
+        var number: Int
+
+        var confirmation: Confirmation
+
+        var body: some View {
+            confirmation()
+            #if os(iOS)
+            return Color(uiColor: number.isEven ? .red : .blue)
+            #elseif os(macOS)
+            return Color(nsColor: number.isEven ? .red : .blue)
+            #endif
+        }
+    }
+
+    struct NonEquatableNumberViewWrapper: View {
+        @State private var count = 0
+
+        var confirmation: Confirmation
+        var continuation: UnsafeContinuation<Void, Never>
+
+        var body: some View {
+            NonEquatableNumberView(number: count, confirmation: confirmation)
+                .onAppear {
+                    DispatchQueue.main.async {
+                        count += 2
+                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                            count += 2
+                            continuation.resume()
+                        }
+                    }
+                }
+        }
+    }
+
+    struct EquatableNumberView: View, Equatable {
+        var number: Int
+
+        var confirmation: Confirmation
+
+        var body: some View {
+            confirmation()
+            #if os(iOS)
+            return Color(uiColor: number.isEven ? .red : .blue)
+            #elseif os(macOS)
+            return Color(nsColor: number.isEven ? .red : .blue)
+            #endif
+        }
+
+        nonisolated static func == (lhs: Self, rhs: Self) -> Bool {
+            lhs.number.isEven == rhs.number.isEven
+        }
+    }
+
+    struct EquatableNumberViewWrapper: View {
+        @State private var count = 0
+
+        var confirmation: Confirmation
+        var continuation: UnsafeContinuation<Void, Never>
+
+        var body: some View {
+            EquatableNumberView(number: count, confirmation: confirmation)
+                .equatable()
+                .onAppear {
+                    DispatchQueue.main.async {
+                        count += 2
+                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                            count += 2
+                            continuation.resume()
+                        }
+                    }
+                }
+        }
+    }
+
+    @Test
+    func nonEquatable() async throws {
+        #if os(iOS)
+        let expectedCount = 1 // FIXME: Not expected, probably due to triggerLayout implementation
+        #elseif os(macOS)
+        let expectedCount = 2 ... 3 // FIXME: Not expected, local 3 while CI 2 :(
+        #endif
+        await confirmation(expectedCount: expectedCount) { @MainActor confirmation in
+            await withUnsafeContinuation { (continuation: UnsafeContinuation<Void, Never>) in
+                let vc = PlatformHostingController(
+                    rootView: NonEquatableNumberViewWrapper(
+                        confirmation: confirmation,
+                        continuation: continuation
+                    )
+                )
+                vc.triggerLayout()
+                workaroundIssue87(vc)
+            }
+        }
+    }
+
+    @Test
+    func equatable() async throws {
+        #if os(iOS)
+        let expectedCount = 1 // FIXME: Not expected, probably due to triggerLayout implementation
+        #elseif os(macOS)
+        let expectedCount = 2
+        #endif
+        await confirmation(expectedCount: expectedCount) { @MainActor confirmation in
+            await withUnsafeContinuation { (continuation: UnsafeContinuation<Void, Never>) in
+                let vc = PlatformHostingController(
+                    rootView: EquatableNumberViewWrapper(
+                        confirmation: confirmation,
+                        continuation: continuation
+                    )
+                )
+                vc.triggerLayout()
+                workaroundIssue87(vc)
+            }
+        }
+    }
+
+    #if !OPENSWIFTUI_COMPATIBILITY_TEST
+    struct Number: Equatable {
+        var value: Int
+
+        static func == (lhs: Self, rhs: Self) -> Bool {
+            lhs.value.isEven == rhs.value.isEven
+        }
+    }
+
+    struct EquatableProxyNumberViewWrapper: View {
+        @State private var count = 0
+
+        var confirmation: Confirmation
+        var continuation: UnsafeContinuation<Void, Never>
+
+        var body: some View {
+            NonEquatableNumberView(number: count, confirmation: confirmation)
+                .equatableProxy(Number(value: count))
+                .onAppear {
+                    DispatchQueue.main.async {
+                        count += 2
+                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                            count += 2
+                            continuation.resume()
+                        }
+                    }
+                }
+        }
+    }
+
+    @Test
+    func equatableProxy() async throws {
+        await confirmation(expectedCount: 1) { @MainActor confirmation in
+            await withUnsafeContinuation { (continuation: UnsafeContinuation<Void, Never>) in
+                let vc = PlatformHostingController(
+                    rootView: EquatableProxyNumberViewWrapper(
+                        confirmation: confirmation,
+                        continuation: continuation
+                    )
+                )
+                vc.triggerLayout()
+                workaroundIssue87(vc)
+            }
+        }
+    }
+    #endif
+}
+
+extension Int {
+    fileprivate var isEven: Bool { self % 2 == 0 }
+}
+#endif