Fiber fixes attempt 2

Sources/TokamakCore/Fiber/Fiber.swift

@@ -63,9 +63,6 @@ public extension FiberReconciler {
     /// Stored as an IUO because it uses `bindProperties` to create the underlying instance.
     var layout: AnyLayout?
 
-    /// The identity of this `View`
-    var id: Identity?
-
     /// The mounted element, if this is a `Renderer` primitive.
     var element: Renderer.ElementType?
 
@@ -135,9 +132,26 @@ public extension FiberReconciler {
       }
     }
 
-    public enum Identity: Hashable {
-      case explicit(AnyHashable)
-      case structural(index: Int)
+    /// The explicit identity of this `View`, if provided
+    var explicitId: AnyHashable? {
+      guard case let .view(v as _AnyIDView, _) = content else { return nil }
+      return v.anyId
+    }
+
+    /// Direct children of this fiber, keyed by their index
+    var mappedChildren: [Int: Fiber] {
+      var map = [Int: Fiber]()
+
+      var currentIndex = 0
+      var currentChild = child
+
+      while let aChild = currentChild {
+        map[currentIndex] = aChild
+        currentIndex += 1
+        currentChild = aChild.sibling
+      }
+
+      return map
     }
 
     init<V: View>(
@@ -390,8 +404,9 @@ public extension FiberReconciler {
         layout = (view as? _AnyLayout)?._erased() ?? DefaultLayout.shared
       }
 
-      if Renderer.isPrimitive(view) {
-        return .init(from: view, useDynamicLayout: reconciler?.renderer.useDynamicLayout ?? false)
+      if Renderer.isPrimitive(view), let element = element {
+        let newContent = Renderer.ElementType.Content(from: view, useDynamicLayout: reconciler?.renderer.useDynamicLayout ?? false)
+        return (element.content != newContent) ? newContent : nil
       } else {
         return nil
       }

Sources/TokamakCore/Fiber/FiberReconciler+TreeReducer.swift

@@ -27,33 +27,35 @@ extension FiberReconciler {
       unowned var parent: Result?
       var child: Result?
       var sibling: Result?
-      var newContent: Renderer.ElementType.Content?
-      var elementIndices: [ObjectIdentifier: Int]
       var nextTraits: _ViewTraitStore
 
       // For reducing
       var lastSibling: Result?
-      var nextExisting: Fiber?
-      var nextExistingAlternate: Fiber?
+      var processedChildCount: Int
+      var unclaimedCurrentChildren: [Int: Fiber]
+
+      // Side-effects
+      var didInsert: Bool
+      var newContent: Renderer.ElementType.Content?
 
       init(
         fiber: Fiber?,
+        currentChildren: [Int: Fiber],
         visitChildren: @escaping (TreeReducer.SceneVisitor) -> (),
         parent: Result?,
-        child: Fiber?,
-        alternateChild: Fiber?,
         newContent: Renderer.ElementType.Content? = nil,
-        elementIndices: [ObjectIdentifier: Int],
         nextTraits: _ViewTraitStore
       ) {
         self.fiber = fiber
         self.visitChildren = visitChildren
         self.parent = parent
-        nextExisting = child
-        nextExistingAlternate = alternateChild
-        self.newContent = newContent
-        self.elementIndices = elementIndices
         self.nextTraits = nextTraits
+
+        processedChildCount = 0
+        unclaimedCurrentChildren = currentChildren
+
+        didInsert = false
+        self.newContent = nil
       }
     }
 
@@ -75,7 +77,8 @@ extension FiberReconciler {
         update: { fiber, scene, _, _ in
           fiber.update(with: &scene)
         },
-        visitChildren: { $1._visitChildren }
+        visitChildren: { $1._visitChildren },
+        isPrimitive: { _ in false }
       )
     }
 
@@ -107,6 +110,9 @@ extension FiberReconciler {
         },
         visitChildren: { reconciler, view in
           reconciler?.renderer.viewVisitor(for: view) ?? view._visitChildren
+        },
+        isPrimitive: { view in
+          Renderer.isPrimitive(view)
         }
       )
     }
@@ -125,78 +131,69 @@ extension FiberReconciler {
         FiberReconciler?
       ) -> Fiber,
       update: (Fiber, inout T, Int?, _ViewTraitStore) -> Renderer.ElementType.Content?,
-      visitChildren: (FiberReconciler?, T) -> (TreeReducer.SceneVisitor) -> ()
+      visitChildren: (FiberReconciler?, T) -> (TreeReducer.SceneVisitor) -> (),
+      isPrimitive: (T) -> Bool
     ) {
       // Create the node and its element.
       var nextValue = nextValue
 
+      let explicitId = (nextValue as? _AnyIDView)?.anyId
+      let childIndex = partialResult.processedChildCount
+
       let resultChild: Result
-      if let existing = partialResult.nextExisting {
-        // If a fiber already exists, simply update it with the new view.
-        let key: ObjectIdentifier?
-        if let elementParent = existing.elementParent {
-          key = ObjectIdentifier(elementParent)
-        } else {
-          key = nil
-        }
-        let newContent = update(
-          existing,
-          &nextValue,
-          key.map { partialResult.elementIndices[$0, default: 0] },
-          partialResult.nextTraits
-        )
+      if let existing = partialResult.unclaimedCurrentChildren[childIndex],
+         existing.typeInfo?.type == typeInfo(of: T.self)?.type,
+         existing.explicitId == explicitId
+      {
+        partialResult.unclaimedCurrentChildren.removeValue(forKey: childIndex)
+        existing.sibling = nil
+        let traits = isPrimitive(nextValue) ? .init() : partialResult.nextTraits
+        let c = update(existing, &nextValue, nil, traits)
         resultChild = Result(
           fiber: existing,
+          currentChildren: existing.mappedChildren,
           visitChildren: visitChildren(partialResult.fiber?.reconciler, nextValue),
           parent: partialResult,
-          child: existing.child,
-          alternateChild: existing.alternate?.child,
-          newContent: newContent,
-          elementIndices: partialResult.elementIndices,
-          nextTraits: existing.element != nil ? .init() : partialResult.nextTraits
+          nextTraits: traits
         )
-        partialResult.nextExisting = existing.sibling
-        partialResult.nextExistingAlternate = partialResult.nextExistingAlternate?.sibling
+        resultChild.newContent = c
       } else {
         let elementParent = partialResult.fiber?.element != nil
           ? partialResult.fiber
           : partialResult.fiber?.elementParent
         let preferenceParent = partialResult.fiber?.preferences != nil
           ? partialResult.fiber
           : partialResult.fiber?.preferenceParent
-        let key: ObjectIdentifier?
-        if let elementParent = elementParent {
-          key = ObjectIdentifier(elementParent)
-        } else {
-          key = nil
-        }
-        // Otherwise, create a new fiber for this child.
         let fiber = createFiber(
           &nextValue,
-          partialResult.nextExistingAlternate?.element,
+          nil,
           partialResult.fiber,
           elementParent,
           preferenceParent,
-          key.map { partialResult.elementIndices[$0, default: 0] },
+          nil,
           partialResult.nextTraits,
           partialResult.fiber?.reconciler
         )
-
-        // If a fiber already exists for an alternate, link them.
-        if let alternate = partialResult.nextExistingAlternate {
-          fiber.alternate = alternate
-          partialResult.nextExistingAlternate = alternate.sibling
+        let traits: _ViewTraitStore
+        if isPrimitive(nextValue) {
+          traits = .init()
+        } else {
+          traits = partialResult.nextTraits
         }
+
         resultChild = Result(
           fiber: fiber,
+          currentChildren: [:],
           visitChildren: visitChildren(partialResult.fiber?.reconciler, nextValue),
           parent: partialResult,
-          child: nil,
-          alternateChild: fiber.alternate?.child,
-          elementIndices: partialResult.elementIndices,
-          nextTraits: fiber.element != nil ? .init() : partialResult.nextTraits
+          nextTraits: traits
         )
+
+        resultChild.didInsert = true
       }
+
+      partialResult.processedChildCount += 1
+
       // Get the last child element we've processed, and add the new child as its sibling.
       if let lastSibling = partialResult.lastSibling {
         lastSibling.fiber?.sibling = resultChild.fiber

Sources/TokamakCore/Fiber/FiberReconciler.swift

@@ -195,11 +195,10 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
       }
       let rootResult = TreeReducer.Result(
         fiber: alternateRoot, // The alternate is the WIP node.
+        currentChildren: root.mappedChildren,
         visitChildren: visitChildren,
         parent: nil,
-        child: alternateRoot?.child,
-        alternateChild: root.child,
-        elementIndices: [:],
+        newContent: nil,
         nextTraits: .init()
       )
       reconciler.caches.clear()

Sources/TokamakCore/Fiber/Mutation.swift

@@ -24,11 +24,6 @@ public enum Mutation<Renderer: FiberRenderer> {
     index: Int
   )
   case remove(element: Renderer.ElementType, parent: Renderer.ElementType?)
-  case replace(
-    parent: Renderer.ElementType,
-    previous: Renderer.ElementType,
-    replacement: Renderer.ElementType
-  )
   case update(
     previous: Renderer.ElementType,
     newContent: Renderer.ElementType.Content,