Dismiss presented controller when parent controller goes away (#192)

* Dismiss presented controller when parent controller goes away

This brings parity with SwiftUI, where if a view disappears, an attached
sheet disappears shortly thereafter.

* wip

* wip

Examples/CaseStudiesTests/PresentationTests.swift

@@ -301,7 +301,7 @@ final class PresentationTests: XCTestCase {
 
   @MainActor
   func testPushFireAndForget_PushStateDriven() async throws {
-    let nav = UINavigationController(rootViewController: UIViewController())
+    let nav = UINavigationController(rootViewController: ViewController())
     try await setUp(controller: nav)
     await assertEventuallyEqual(nav.viewControllers.count, 1)
 
@@ -321,7 +321,7 @@ final class PresentationTests: XCTestCase {
 
   @MainActor
   func testDismissMultiplePresentations() async throws {
-    class VC: UIViewController {
+    class VC: ViewController {
       @UIBinding var isPresented = false
       override func viewDidLoad() {
         super.viewDidLoad()
@@ -344,17 +344,8 @@ final class PresentationTests: XCTestCase {
 
   @MainActor
   func testDismissLeafPresentationDirectly() async throws {
-    class VC: UIViewController {
+    class VC: ViewController {
       @UIBinding var isPresented = false
-      override func loadView() {
-        super.loadView()
-        view.backgroundColor = .init(
-          red: .random(in: 0...1),
-          green: .random(in: 0...1),
-          blue: .random(in: 0...1),
-          alpha: 1
-        )
-      }
       override func viewDidLoad() {
         super.viewDidLoad()
         present(isPresented: $isPresented) { VC() }
@@ -376,17 +367,8 @@ final class PresentationTests: XCTestCase {
   }
 
   @MainActor func testDismissMiddlePresentation() async throws {
-    class VC: UIViewController {
+    class VC: ViewController {
       @UIBinding var isPresented = false
-      override func loadView() {
-        super.loadView()
-        view.backgroundColor = .init(
-          red: .random(in: 0...1),
-          green: .random(in: 0...1),
-          blue: .random(in: 0...1),
-          alpha: 1
-        )
-      }
       override func viewDidLoad() {
         super.viewDidLoad()
         present(isPresented: $isPresented) { VC() }
@@ -414,8 +396,31 @@ final class PresentationTests: XCTestCase {
     await assertEventuallyNil(vc.presentedViewController?.presentedViewController, timeout: 2)
   }
 
-  @MainActor func testDoublePresentation_ChangeRootBinding() async throws {
+  @MainActor func testNestedPresentationParentDismissalDismissesChild() async throws {
+    let nav = UINavigationController(rootViewController: ViewController())
+    try await setUp(controller: nav)
+    await assertEventuallyEqual(nav.viewControllers.count, 1)
+
+    var child: BasicViewController? = BasicViewController(model: Model())
+    nav.pushViewController(child!, animated: false)
+    await assertEventuallyEqual(nav.viewControllers.count, 2)
+
+    try await Task.sleep(for: .seconds(0.5))
+    withUITransaction(\.uiKit.disablesAnimations, true) {
+      child!.model.isPresented = true
+    }
+    try await Task.sleep(for: .seconds(0.5))
 
+    await assertEventuallyNotNil(child!.presentedViewController)
+    XCTAssertEqual(child!.presentedViewController, nav.presentedViewController)
+    nav.popToRootViewController(animated: false)
+    try await Task.sleep(for: .seconds(0.5))
+
+    child = nil
+    try await Task.sleep(for: .seconds(0.5))
+
+    await assertEventuallyEqual(nav.viewControllers.count, 1)
+    await assertEventuallyNil(nav.presentedViewController)
   }
 }
 
@@ -441,6 +446,18 @@ private final class Model: Identifiable {
   }
 }
 
+private class ViewController: UIViewController {
+  override func viewDidLoad() {
+    view.backgroundColor = .init(
+      red: .random(in: 0...1),
+      green: .random(in: 0...1),
+      blue: .random(in: 0...1),
+      alpha: 1
+    )
+    super.viewDidLoad()
+  }
+}
+
 private class BasicViewController: UIViewController {
   @UIBindable var model: Model
   var isPresenting = false
@@ -463,7 +480,7 @@ private class BasicViewController: UIViewController {
       self?.isPresenting = false
     } content: { [weak self] in
       self?.isPresenting = true
-      return UIViewController()
+      return ViewController()
     }
     present(item: $model.presentedChild) { [weak self] in
       self?.isPresenting = false
@@ -472,7 +489,7 @@ private class BasicViewController: UIViewController {
       return BasicViewController(model: model)
     }
     navigationDestination(isPresented: $model.isPushed) {
-      UIViewController()
+      ViewController()
     }
     navigationDestination(item: $model.pushedChild) { model in
       BasicViewController(model: model)

Sources/UIKitNavigation/Navigation/Presentation.swift

@@ -443,9 +443,18 @@
     }
   }
 
+  @MainActor
   private class Presented {
     weak var controller: UIViewController?
     let presentationID: AnyHashable?
+    deinit {
+      // NB: This can only be assumed because it is held in a UIViewController and is guaranteed to
+      //     deinit alongside it on the main thread. If we use this other places we should force it
+      //     to be a UIViewController as well, to ensure this functionality.
+      MainActor.assumeIsolated {
+        self.controller?.dismiss(animated: false)
+      }
+    }
     init(_ controller: UIViewController, id presentationID: AnyHashable? = nil) {
       self.controller = controller
       self.presentationID = presentationID