Add `print` statements to reproduce the issue

Sources/TokamakCore/MountedViews/MountedCompositeView.swift

@@ -80,7 +80,9 @@ final class MountedCompositeView<R: Renderer>: MountedCompositeElement<R> {
   }
 
   override func update(with reconciler: StackReconciler<R>) {
+    print("C.render")
     let element = reconciler.render(compositeView: self)
+    print("C.recon")
     reconciler.reconcile(
       self,
       with: element,
@@ -91,5 +93,6 @@ final class MountedCompositeView<R: Renderer>: MountedCompositeElement<R> {
       },
       mountChild: { $0.makeMountedView(parentTarget, environmentValues, self) }
     )
+    print("C.done")
   }
 }

Sources/TokamakCore/MountedViews/MountedElement.swift

@@ -126,6 +126,7 @@ public class MountedElement<R: Renderer> {
     case .view:
       environmentValues.inject(into: &view.view, type)
     }
+    print("updateEnvironment done")
   }
 
   func mount(
@@ -160,10 +161,12 @@ public class MountedElement<R: Renderer> {
 
 extension EnvironmentValues {
   mutating func inject(into element: inout Any, _ type: Any.Type) {
+    print("Inj.typeInfo")
     guard let info = typeInfo(of: type) else { return }
 
     // Extract the view from the AnyView for modification, apply Environment changes:
     if let container = element as? ModifierContainer {
+      print("Inj.container")
       container.environmentModifier?.modifyEnvironment(&self)
     }
 
@@ -174,19 +177,26 @@ extension EnvironmentValues {
     for dynamicProp in info.properties.filter({ $0.type is DynamicProperty.Type }) {
       guard let propInfo = typeInfo(of: dynamicProp.type) else { return }
       var propWrapper = dynamicProp.get(from: element) as! DynamicProperty
+      print("Inj.prop.pi \(propInfo.properties.count)")
       for prop in propInfo.properties.filter({ $0.type is EnvironmentReader.Type }) {
         var wrapper = prop.get(from: propWrapper) as! EnvironmentReader
+        print("*****Inj.prop.pi.prop.setC *****")
         wrapper.setContent(from: self)
+        print("*****Inj.prop.pi.prop.set *****")
         prop.set(value: wrapper, on: &propWrapper)
       }
+      print("***** Inj.prop.dynamic.set \(dynamicProp.type) *****")
       dynamicProp.set(value: propWrapper, on: &element)
     }
     for prop in info.properties.filter({ $0.type is EnvironmentReader.Type }) {
       var wrapper = prop.get(from: element) as! EnvironmentReader
+      print("***** Inj.prop.env.setC \(wrapper) *****")
       wrapper.setContent(from: self)
+      print("***** Inj.prop.env.set \(prop.type) *****")
       prop.set(value: wrapper, on: &element)
     }
     // swiftlint:enable force_cast
+    print("Inj.done")
   }
 }
 

Sources/TokamakCore/MountedViews/MountedHostView.swift

@@ -83,15 +83,25 @@ public final class MountedHostView<R: Renderer>: MountedElement<R> {
     }
   }
 
+  private var __mountedChild = 0
+
   override func update(with reconciler: StackReconciler<R>) {
     guard let target = target else { return }
 
+    let myStack = __stack
+    __stack += 1
+
+    print("Host.upEnv")
     updateEnvironment()
     target.view = view
+    print(
+      "Host.renderer?.update \(reconciler.renderer == nil ? "nil" : "\(Swift.type(of: reconciler.renderer!))")"
+    )
     reconciler.renderer?.update(target: target, with: self)
 
     var childrenViews = view.children
 
+    print("Host(\(mountedChildren.isEmpty),\(childrenViews.isEmpty)")
     switch (mountedChildren.isEmpty, childrenViews.isEmpty) {
     // if existing children present and new children array is empty
     // then unmount all existing children
@@ -113,10 +123,17 @@ public final class MountedHostView<R: Renderer>: MountedElement<R> {
       // run simple update
       while let mountedChild = mountedChildren.first, let childView = childrenViews.first {
         let newChild: MountedElement<R>
+        print(
+          "BEGIN todo: \(myStack).\(mountedChildren.count) \(childView.typeConstructorName == mountedChildren[0].view.typeConstructorName ? "a - \(childView.typeConstructorName)" : "b")"
+        )
+        __mountedChild += 1
         if childView.typeConstructorName == mountedChildren[0].view.typeConstructorName {
           mountedChild.environmentValues = environmentValues
           mountedChild.view = childView
           mountedChild.updateEnvironment()
+          print(
+            "update -> \(Swift.type(of: mountedChild)), recon -> \(Swift.type(of: reconciler)))"
+          )
           mountedChild.update(with: reconciler)
           newChild = mountedChild
         } else {
@@ -131,6 +148,8 @@ public final class MountedHostView<R: Renderer>: MountedElement<R> {
         newChildren.append(newChild)
         mountedChildren.removeFirst()
         childrenViews.removeFirst()
+
+        print("END mountedChild todo: \(myStack).\(mountedChildren.count)")
       }
 
       // more mounted views left than views were to be rendered:
@@ -150,6 +169,7 @@ public final class MountedHostView<R: Renderer>: MountedElement<R> {
         }
       }
 
+      __stack -= 1
       mountedChildren = newChildren
 
     // both arrays are empty, nothing to reconcile
@@ -157,3 +177,5 @@ public final class MountedHostView<R: Renderer>: MountedElement<R> {
     }
   }
 }
+
+private var __stack = 0

Sources/TokamakCore/Reflection/Models/TypeInfo.swift

@@ -50,8 +50,12 @@ public struct TypeInfo {
 
 public func typeInfo(of type: Any.Type) -> TypeInfo? {
   guard Kind(type: type) == .struct else {
+    print("TypeInfo: nil")
     return nil
   }
 
-  return StructMetadata(type: type).toTypeInfo()
+  print("TypeInfo: \(type)")
+  let result = StructMetadata(type: type).toTypeInfo()
+  print("TypeInfo.done")
+  return result
 }

Sources/TokamakCore/StackReconciler.swift

@@ -206,27 +206,35 @@ public final class StackReconciler<R: Renderer> {
     body bodyKeypath: ReferenceWritableKeyPath<MountedCompositeElement<R>, Any>,
     result: KeyPath<MountedCompositeElement<R>, (Any) -> T>
   ) -> T {
+    print("SR.env")
     compositeElement.updateEnvironment()
+    print("SR.type")
     if let info = typeInfo(of: compositeElement.type) {
       var stateIdx = 0
+      print("SR.dynamicProps")
       let dynamicProps = info.dynamicProperties(
         &compositeElement.environmentValues,
         source: &compositeElement[keyPath: bodyKeypath]
       )
+      print("SR.dynamicProps.done")
 
       compositeElement.transientSubscriptions = []
       for property in dynamicProps {
+        print("SR.begin")
         // Setup state/subscriptions
         if property.type is ValueStorage.Type {
+          print("SR.setup storage")
           setupStorage(id: stateIdx, for: property, of: compositeElement, body: bodyKeypath)
           stateIdx += 1
         }
         if property.type is ObservedProperty.Type {
+          print("SR.setup sub")
           setupTransientSubscription(for: property, of: compositeElement, body: bodyKeypath)
         }
+        print("SR.done")
       }
     }
-
+    print("SR.type.done")
     return compositeElement[keyPath: result](compositeElement[keyPath: bodyKeypath])
   }
 

Sources/TokamakDemo/main.swift

@@ -1,40 +1,27 @@
-// Copyright 2020 Tokamak contributors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 import TokamakShim
 
-@available(OSX 10.16, iOS 14.0, *)
-struct CustomScene: Scene {
-  @Environment(\.scenePhase) private var scenePhase
-
+struct TokamakApp: App {
   var body: some Scene {
-    print("In CustomScene.body scenePhase is \(scenePhase)")
-    return WindowGroup("Tokamak Demo") {
-      TokamakDemoView()
+    WindowGroup("Spooky Hanger") {
+      NavigationView {
+        List {
+          ForEach(["Section"], id: \.self) { section in
+            Section(header: Text(section).font(.headline)) {
+              ForEach(["Item 1"], id: \.self) { childRow in
+                NavigationLink(
+                  destination: Text(childRow).padding([.leading, .trailing])
+                ) {
+                  Text(childRow)
+                }
+                .padding(.leading)
+              }
+            }
+          }
+        }
+        .listStyle(SidebarListStyle())
+      }
     }
   }
 }
 
-@available(OSX 10.16, iOS 14.0, *)
-struct TokamakDemoApp: App {
-  var body: some Scene {
-    CustomScene()
-  }
-}
-
-// If @main was supported for executable Swift Packages,
-// this would match SwiftUI 100%
-if #available(OSX 10.16, iOS 14.0, *) {
-  TokamakDemoApp.main()
-}
+TokamakApp.main()