Bring back actor proxy for observe isolation (#316)

* Bring back actor proxy for `observe` isolation

While `NSObject.observe` still behaved just fine,
`SwiftNavigation.observe` could execute on the wrong actor.

* Use @_inheritActorContext @isolated(any).isolation instead of #isolation macro (#317)

* Use @_inheritActorContext @isolated(any).isolation instead of #isolation macro

* Fix IsolationTests

* wip

---------

Co-authored-by: Maxim Krouk <[email protected]>

Author: stephencelis

Package.resolved

@@ -53,7 +53,8 @@ let package = Package(
     .testTarget(
       name: "SwiftNavigationTests",
       dependencies: [
-        "SwiftNavigation"
+        "SwiftNavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
     .target(
@@ -67,7 +68,8 @@ let package = Package(
     .testTarget(
       name: "SwiftUINavigationTests",
       dependencies: [
-        "SwiftUINavigation"
+        "SwiftUINavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
     .target(
@@ -91,7 +93,8 @@ let package = Package(
     .testTarget(
       name: "UIKitNavigationTests",
       dependencies: [
-        "UIKitNavigation"
+        "UIKitNavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
   ]

Package.swift

@@ -53,7 +53,8 @@ let package = Package(
     .testTarget(
       name: "SwiftNavigationTests",
       dependencies: [
-        "SwiftNavigation"
+        "SwiftNavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
     .target(
@@ -67,7 +68,8 @@ let package = Package(
     .testTarget(
       name: "SwiftUINavigationTests",
       dependencies: [
-        "SwiftUINavigation"
+        "SwiftUINavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
     .target(
@@ -91,7 +93,8 @@ let package = Package(
     .testTarget(
       name: "UIKitNavigationTests",
       dependencies: [
-        "UIKitNavigation"
+        "UIKitNavigation",
+        .product(name: "IssueReportingTestSupport", package: "xctest-dynamic-overlay"),
       ]
     ),
   ],

[email protected]

@@ -56,9 +56,13 @@ import ConcurrencyExtras
   /// - Returns: A token that keeps the subscription alive. Observation is cancelled when the token
   ///   is deallocated.
   public func observe(
-    @_inheritActorContext _ apply: @escaping @isolated(any) @Sendable () -> Void
+    @_inheritActorContext
+    _ apply: @escaping @isolated(any) @Sendable () -> Void
   ) -> ObserveToken {
-    observe { _ in Result(catching: apply).get() }
+    _observe(
+      isolation: apply.isolation,
+      { _ in Result(catching: apply).get() }
+    )
   }
 
   /// Tracks access to properties of an observable model.
@@ -75,24 +79,34 @@ import ConcurrencyExtras
     _ apply: @escaping @isolated(any) @Sendable (_ transaction: UITransaction) -> Void
   ) -> ObserveToken {
     _observe(
-      apply,
-      task: { transaction, operation in
-        Task {
-          await operation()
-        }
-      }
+      isolation: apply.isolation,
+      apply
     )
   }
 #endif
 
 func _observe(
-  _ apply: @escaping @Sendable (_ transaction: UITransaction) -> Void,
-  task:
-    @escaping @Sendable (
-      _ transaction: UITransaction, _ operation: @escaping @Sendable () -> Void
-    ) -> Void = {
-      Task(operation: $1)
+  isolation: (any Actor)?,
+  _ apply: @escaping @Sendable (_ transaction: UITransaction) -> Void
+) -> ObserveToken {
+  let actor = ActorProxy(base: isolation)
+  return _observe(
+    apply,
+    task: { transaction, operation in
+      Task {
+        await actor.perform {
+          operation()
+        }
+      }
     }
+  )
+}
+
+func _observe(
+  _ apply: @escaping @Sendable (_ transaction: UITransaction) -> Void,
+  task: @escaping @Sendable (
+    _ transaction: UITransaction, _ operation: @escaping @Sendable () -> Void
+  ) -> Void
 ) -> ObserveToken {
   let token = ObserveToken()
   onChange(
@@ -124,10 +138,9 @@ func _observe(
 
 private func onChange(
   _ apply: @escaping @Sendable (_ transaction: UITransaction) -> Void,
-  task:
-    @escaping @Sendable (
-      _ transaction: UITransaction, _ operation: @escaping @isolated(any) @Sendable () -> Void
-    ) -> Void
+  task: @escaping @Sendable (
+    _ transaction: UITransaction, _ operation: @escaping @Sendable () -> Void
+  ) -> Void
 ) {
   withPerceptionTracking {
     apply(.current)
@@ -200,3 +213,16 @@ public final class ObserveToken: Sendable, HashableObject {
     set.insert(self)
   }
 }
+
+private actor ActorProxy {
+  let base: (any Actor)?
+  init(base: (any Actor)?) {
+    self.base = base
+  }
+  nonisolated var unownedExecutor: UnownedSerialExecutor {
+    (base ?? MainActor.shared).unownedExecutor
+  }
+  func perform(_ operation: @Sendable () -> Void) {
+    operation()
+  }
+}

Sources/SwiftNavigation/Observe.swift

@@ -27,7 +27,8 @@
 
           Asynchronous actions cannot be animated. Evaluate this action in a synchronous closure, \
           or use 'SwiftUI.withAnimation' explicitly.
-          """)
+          """
+        )
       }
     }
   }