Fix EnvironmentKeyTransformModifier implementation (#533)

Author: Kyle-Ye

Sources/OpenSwiftUICore/Data/Environment/EnvironmentKeyTransformModifier.swift

@@ -96,14 +96,16 @@ private struct ChildEnvironment<Value>: StatefulRule, AsyncAttribute, CustomStri
             }
         }
         let valueChanged = if !environmentChanged {
-            // FIXME: The map logic is buggy
-            oldValue.map{ compareValues($0, newValue, mode: .equatableUnlessPOD) } ?? true
+            // SwiftUI implementation:
+            // oldValue.map { compareValues($0, newValue, mode: .equatableUnlessPOD) } ?? true
+            oldValue.map{ !compareValues($0, newValue, mode: .equatableUnlessPOD) } ?? true
         } else {
             true
         }
         let keyPathChanged = if !valueChanged {
-            // FIXME: The map logic is buggy
-            oldKeyPath.map({ $0 == newKeyPath }) ?? true
+            // SwiftUI implementation:
+            // oldKeyPath.map { $0 === newKeyPath } ?? true
+            oldKeyPath.map{ $0 !== newKeyPath } ?? true
         } else {
             true
         }

Tests/OpenSwiftUICompatibilityTests/Data/Environment/EnvironmentKeyTransformModifierCompatibilityTests.swift

@@ -7,6 +7,12 @@ import Testing
 
 extension EnvironmentValues {
     @Entry fileprivate var customValue = 0
+    @Entry fileprivate var customValue2 = 0
+}
+
+@Observable
+private final class Model {
+    var value = 0
 }
 
 @MainActor
@@ -36,4 +42,67 @@ struct EnvironmentKeyTransformModifierCompatibilityTests {
             )
         }
     }
+
+    @Test
+    func environmentKeyTransformDifferentKeyPath() async throws {
+        @MainActor
+        enum Count {
+            static var contentBody: Int = 0
+            static var subviewBody: Int = 0
+        }
+
+        struct ContentView: View {
+            @State private var model = Model()
+
+            var body: some View {
+                let _ = {
+                    Count.contentBody += 1
+                }()
+                Subview()
+                    .transformEnvironment(model.value == 0 ? \.customValue : \.customValue2) {
+                        $0 = model.value
+                    }
+                    .onAppear {
+                        model.value = 2
+                    }
+            }
+        }
+
+        struct Subview: View {
+            @Environment(\.customValue) private var value
+            @Environment(\.customValue2) private var value2
+
+            var body: some View {
+                let _ = {
+                    Count.subviewBody += 1
+                    switch Count.subviewBody {
+                    case 1:
+                        #expect(value == 0)
+                        #expect(value2 == 0)
+                    case 2:
+                        #expect(value == 0)
+                        #if OPENSWIFTUI
+                        #expect(value2 == 2)
+                        #else
+                        // SwiftUI known implementation issue
+                        withKnownIssue {
+                            #expect(value2 == 2)
+                        }
+                        #expect(value2 == 0)
+                        #endif
+                    default:
+                        Issue.record()
+                    }
+                }()
+                Color.red
+            }
+        }
+        try await triggerLayoutWithWindow(expectedCount: 0) { _ in
+            PlatformHostingController(
+                rootView: ContentView()
+            )
+        }
+        #expect(Count.contentBody == 2)
+        #expect(Count.subviewBody == 2)
+    }
 }