Named events tracking (#49298)

Author: SteveSandersonMS

src/Components/Components/perf/RenderTreeDiffBuilderBenchmark.cs

@@ -79,7 +79,7 @@ public RenderTreeDiffBuilderBenchmark()
     public void ComputeDiff_SingleFormField()
     {
         builder.ClearStateForCurrentBatch();
-        var diff = RenderTreeDiffBuilder.ComputeDiff(renderer, builder, 0, modified.GetFrames(), original.GetFrames(), original.GetNamedEvents());
+        var diff = RenderTreeDiffBuilder.ComputeDiff(renderer, builder, 0, modified.GetFrames(), original.GetFrames());
         GC.KeepAlive(diff);
     }
 

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -27,13 +27,23 @@ Microsoft.AspNetCore.Components.NavigationManager.ToAbsoluteUri(string? relative
 Microsoft.AspNetCore.Components.Rendering.ComponentState.LogicalParentComponentState.get -> Microsoft.AspNetCore.Components.Rendering.ComponentState?
 Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddComponentParameter(int sequence, string! name, Microsoft.AspNetCore.Components.IComponentRenderMode! renderMode) -> void
 Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddComponentRenderMode(int sequence, Microsoft.AspNetCore.Components.IComponentRenderMode! renderMode) -> void
-Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.SetEventHandlerName(string! eventHandlerName) -> void
 *REMOVED*Microsoft.AspNetCore.Components.RouteData.RouteData(System.Type! pageType, System.Collections.Generic.IReadOnlyDictionary<string!, object!>! routeValues) -> void
 *REMOVED*Microsoft.AspNetCore.Components.RouteData.RouteValues.get -> System.Collections.Generic.IReadOnlyDictionary<string!, object!>!
+Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddNamedEvent(int sequence, string! eventType, string! assignedName) -> void
 Microsoft.AspNetCore.Components.RenderTree.ComponentFrameFlags
 Microsoft.AspNetCore.Components.RenderTree.ComponentFrameFlags.HasCallerSpecifiedRenderMode = 1 -> Microsoft.AspNetCore.Components.RenderTree.ComponentFrameFlags
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.AssignedName.get -> string!
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.ComponentId.get -> int
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.EventType.get -> string!
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.FrameIndex.get -> int
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.NamedEvent() -> void
+Microsoft.AspNetCore.Components.RenderTree.NamedEvent.NamedEvent(int componentId, int frameIndex, string! eventType, string! assignedName) -> void
+Microsoft.AspNetCore.Components.RenderTree.RenderBatch.AddedNamedEvents.get -> Microsoft.AspNetCore.Components.RenderTree.ArrayRange<Microsoft.AspNetCore.Components.RenderTree.NamedEvent>?
+Microsoft.AspNetCore.Components.RenderTree.RenderBatch.RemovedNamedEvents.get -> Microsoft.AspNetCore.Components.RenderTree.ArrayRange<Microsoft.AspNetCore.Components.RenderTree.NamedEvent>?
 Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.ComponentFrameFlags.get -> Microsoft.AspNetCore.Components.RenderTree.ComponentFrameFlags
 Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrameType.ComponentRenderMode = 9 -> Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrameType
+Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrameType.NamedEvent = 10 -> Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrameType
 Microsoft.AspNetCore.Components.RouteData.RouteData(System.Type! pageType, System.Collections.Generic.IReadOnlyDictionary<string!, object?>! routeValues) -> void
 Microsoft.AspNetCore.Components.RouteData.RouteValues.get -> System.Collections.Generic.IReadOnlyDictionary<string!, object?>!
 Microsoft.AspNetCore.Components.Routing.IRoutingStateProvider
@@ -91,6 +101,6 @@ virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.AddPendingTask(Micro
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.CreateComponentState(int componentId, Microsoft.AspNetCore.Components.IComponent! component, Microsoft.AspNetCore.Components.Rendering.ComponentState? parentComponentState) -> Microsoft.AspNetCore.Components.Rendering.ComponentState!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(ulong eventHandlerId, Microsoft.AspNetCore.Components.RenderTree.EventFieldInfo? fieldInfo, System.EventArgs! eventArgs, bool quiesce) -> System.Threading.Tasks.Task!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.ResolveComponentForRenderMode(System.Type! componentType, int? parentComponentId, Microsoft.AspNetCore.Components.IComponentActivator! componentActivator, Microsoft.AspNetCore.Components.IComponentRenderMode! renderMode) -> Microsoft.AspNetCore.Components.IComponent!
-virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.ShouldTrackNamedEventHandlers() -> bool
-virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.TrackNamedEventId(ulong eventHandlerId, int componentId, string! eventHandlerName) -> void
 ~Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.ComponentRenderMode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode
+~Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.NamedEventAssignedName.get -> string
+~Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.NamedEventType.get -> string

src/Components/Components/src/RenderTree/NamedEvent.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components.RenderTree;
+
+/// <summary>
+/// Types in the Microsoft.AspNetCore.Components.RenderTree are not recommended for use outside
+/// of the Blazor framework. These types will change in a future release.
+/// </summary>
+/// <remarks>
+/// Constructs an instance of <see cref="NamedEvent"/>.
+/// </remarks>
+/// <param name="componentId">The ID of the component holding the named value.</param>
+/// <param name="frameIndex">The index of the <see cref="RenderTreeFrameType.NamedEvent"/> frame within the component's current render output.</param>
+/// <param name="eventType">The event type.</param>
+/// <param name="assignedName">The application-assigned name.</param>
+public readonly struct NamedEvent(int componentId, int frameIndex, string eventType, string assignedName)
+{
+    /// <summary>
+    /// The ID of the component holding the named event.
+    /// </summary>
+    public readonly int ComponentId { get; } = componentId;
+
+    /// <summary>
+    /// The index of the <see cref="RenderTreeFrameType.NamedEvent"/> frame within the component's current render output.
+    /// </summary>
+    public readonly int FrameIndex { get; } = frameIndex;
+
+    /// <summary>
+    /// The event type.
+    /// </summary>
+    public readonly string EventType { get; } = eventType;
+
+    /// <summary>
+    /// The application-assigned name.
+    /// </summary>
+    public readonly string AssignedName { get; } = assignedName;
+}

src/Components/Components/src/RenderTree/RenderBatch.cs

@@ -33,16 +33,30 @@ public readonly struct RenderBatch
     /// </summary>
     public ArrayRange<ulong> DisposedEventHandlerIDs { get; }
 
+    /// <summary>
+    /// Gets the named events that were added, or null.
+    /// </summary>
+    public ArrayRange<NamedEvent>? AddedNamedEvents { get; }
+
+    /// <summary>
+    /// Gets the named events that were removed, or null.
+    /// </summary>
+    public ArrayRange<NamedEvent>? RemovedNamedEvents { get; }
+
     internal RenderBatch(
         ArrayRange<RenderTreeDiff> updatedComponents,
         ArrayRange<RenderTreeFrame> referenceFrames,
         ArrayRange<int> disposedComponentIDs,
-        ArrayRange<ulong> disposedEventHandlerIDs)
+        ArrayRange<ulong> disposedEventHandlerIDs,
+        ArrayRange<NamedEvent>? addedNamedEvents,
+        ArrayRange<NamedEvent>? removedNamedEvents)
     {
         UpdatedComponents = updatedComponents;
         ReferenceFrames = referenceFrames;
         DisposedComponentIDs = disposedComponentIDs;
         DisposedEventHandlerIDs = disposedEventHandlerIDs;
+        AddedNamedEvents = addedNamedEvents;
+        RemovedNamedEvents = removedNamedEvents;
     }
 }
 

src/Components/Components/src/RenderTree/RenderTreeDiffBuilder.cs

@@ -23,8 +23,7 @@ public static RenderTreeDiff ComputeDiff(
         RenderBatchBuilder batchBuilder,
         int componentId,
         ArrayRange<RenderTreeFrame> oldTree,
-        ArrayRange<RenderTreeFrame> newTree,
-        Dictionary<string, int>? namedEventIndexes)
+        ArrayRange<RenderTreeFrame> newTree)
     {
         var editsBuffer = batchBuilder.EditsBuffer;
         var editsBufferStartLength = editsBuffer.Count;
@@ -35,34 +34,11 @@ public static RenderTreeDiff ComputeDiff(
         var editsSegment = editsBuffer.ToSegment(editsBufferStartLength, editsBuffer.Count);
         var result = new RenderTreeDiff(componentId, editsSegment);
 
-        // Named event handlers name must be unique globally and stable over the time period we are deciding where to
-        // dispatch a given named event.
-        // Once a component has defined a named event handler with a concrete name, no other component instance can
-        // define a named event handler with that name.
-        //
-        // At this stage, we only ensure that the named event handler is unique per component instance, as that,
-        // combined with the check that the EndpointRenderer does, is enough to ensure the uniqueness and the stability
-        // of the named event handler over time **globally**.
-        //
-        // Tracking and uniqueness are enforced when we are trying to dispatch an event to a named event handler, since in
-        // any other case we don't actually track the named event handlers. We do this because:
-        // 1) We don't want to break the user's app if we don't have to.
-        // 2) We don't have to pay the cost of continously tracking all events all the time to throw.
-        // That's why raising the error is delayed until we are forced to make a decission.
-        if (namedEventIndexes != null)
-        {
-            foreach (var (name, index) in namedEventIndexes)
-            {
-                ref var frame = ref newTree.Array[index];
-                renderer.TrackNamedEventId(frame.AttributeEventHandlerId, componentId, name);
-            }
-        }
-
         return result;
     }
 
-    public static void DisposeFrames(RenderBatchBuilder batchBuilder, ArrayRange<RenderTreeFrame> frames)
-        => DisposeFramesInRange(batchBuilder, frames.Array, 0, frames.Count);
+    public static void DisposeFrames(RenderBatchBuilder batchBuilder, int componentId, ArrayRange<RenderTreeFrame> frames)
+        => DisposeFramesInRange(batchBuilder, componentId, frames.Array, 0, frames.Count);
 
     private static void AppendDiffEntriesForRange(
         ref DiffContext diffContext,
@@ -749,6 +725,22 @@ private static void AppendDiffEntriesForFramesWithSameSequence(
                     break;
                 }
 
+            case RenderTreeFrameType.NamedEvent:
+                {
+                    // We don't have a use case for the event types changing, so we don't even check that. We assume for a given sequence number
+                    // the event type is always a constant. What can change is the frame index and the assigned name.
+                    if (oldFrameIndex != newFrameIndex
+                        || !string.Equals(oldFrame.NamedEventAssignedName, newFrame.NamedEventAssignedName, StringComparison.Ordinal))
+                    {
+                        // We could track the updates as a concept in its own right, but this situation will be uncommon,
+                        // so it's enough to treat it as a delete+add
+                        diffContext.BatchBuilder.RemoveNamedEvent(diffContext.ComponentId, oldFrameIndex, ref oldFrame);
+                        diffContext.BatchBuilder.AddNamedEvent(diffContext.ComponentId, newFrameIndex, ref newFrame);
+                    }
+
+                    break;
+                }
+
             // We don't handle attributes here, they have their own diff logic.
             // See AppendDiffEntriesForAttributeFrame
             default:
@@ -844,6 +836,11 @@ private static void InsertNewFrame(ref DiffContext diffContext, int newFrameInde
                     InitializeNewComponentReferenceCaptureFrame(ref diffContext, ref newFrame);
                     break;
                 }
+            case RenderTreeFrameType.NamedEvent:
+                {
+                    InitializeNewNamedEvent(ref diffContext, newFrameIndex);
+                    break;
+                }
             default:
                 throw new NotImplementedException($"Unexpected frame type during {nameof(InsertNewFrame)}: {newFrame.FrameTypeField}");
         }
@@ -868,7 +865,7 @@ private static void RemoveOldFrame(ref DiffContext diffContext, int oldFrameInde
             case RenderTreeFrameType.Element:
                 {
                     var endIndexExcl = oldFrameIndex + oldFrame.ElementSubtreeLengthField;
-                    DisposeFramesInRange(diffContext.BatchBuilder, oldTree, oldFrameIndex, endIndexExcl);
+                    DisposeFramesInRange(diffContext.BatchBuilder, diffContext.ComponentId, oldTree, oldFrameIndex, endIndexExcl);
                     diffContext.Edits.Append(RenderTreeEdit.RemoveFrame(diffContext.SiblingIndex));
                     break;
                 }
@@ -889,6 +886,11 @@ private static void RemoveOldFrame(ref DiffContext diffContext, int oldFrameInde
                     diffContext.Edits.Append(RenderTreeEdit.RemoveFrame(diffContext.SiblingIndex));
                     break;
                 }
+            case RenderTreeFrameType.NamedEvent:
+                {
+                    diffContext.BatchBuilder.RemoveNamedEvent(diffContext.ComponentId, oldFrameIndex, ref diffContext.OldTree[oldFrameIndex]);
+                    break;
+                }
             default:
                 throw new NotImplementedException($"Unexpected frame type during {nameof(RemoveOldFrame)}: {oldFrame.FrameTypeField}");
         }
@@ -944,6 +946,9 @@ private static void InitializeNewSubtree(ref DiffContext diffContext, int frameI
                 case RenderTreeFrameType.ComponentReferenceCapture:
                     InitializeNewComponentReferenceCaptureFrame(ref diffContext, ref frame);
                     break;
+                case RenderTreeFrameType.NamedEvent:
+                    InitializeNewNamedEvent(ref diffContext, i);
+                    break;
             }
         }
     }
@@ -1001,7 +1006,12 @@ private static void InitializeNewComponentReferenceCaptureFrame(ref DiffContext
         newFrame.ComponentReferenceCaptureActionField(componentInstance);
     }
 
-    private static void DisposeFramesInRange(RenderBatchBuilder batchBuilder, RenderTreeFrame[] frames, int startIndex, int endIndexExcl)
+    private static void InitializeNewNamedEvent(ref DiffContext diffContext, int newTreeFrameIndex)
+    {
+        diffContext.BatchBuilder.AddNamedEvent(diffContext.ComponentId, newTreeFrameIndex, ref diffContext.NewTree[newTreeFrameIndex]);
+    }
+
+    private static void DisposeFramesInRange(RenderBatchBuilder batchBuilder, int componentId, RenderTreeFrame[] frames, int startIndex, int endIndexExcl)
     {
         for (var i = startIndex; i < endIndexExcl; i++)
         {
@@ -1014,6 +1024,10 @@ private static void DisposeFramesInRange(RenderBatchBuilder batchBuilder, Render
             {
                 batchBuilder.DisposedEventHandlerIds.Append(frame.AttributeEventHandlerIdField);
             }
+            else if (frame.FrameTypeField == RenderTreeFrameType.NamedEvent)
+            {
+                batchBuilder.RemoveNamedEvent(componentId, i, ref frames[i]);
+            }
         }
     }
 

src/Components/Components/src/RenderTree/RenderTreeFrame.cs

@@ -282,6 +282,25 @@ public IComponentRenderMode ComponentRenderMode
         }
     }
 
+    // --------------------------------------------------------------------------------
+    // RenderTreeFrameType.NamedEvent
+    // --------------------------------------------------------------------------------
+
+    [FieldOffset(16)] internal string NamedEventTypeField;
+    [FieldOffset(24)] internal string NamedEventAssignedNameField;
+
+    /// <summary>
+    /// If the <see cref="FrameType"/> property equals <see cref="RenderTreeFrameType.NamedEvent"/>,
+    /// gets the event type. Otherwise, the value is undefined.
+    /// </summary>
+    public string NamedEventType => NamedEventTypeField;
+
+    /// <summary>
+    /// If the <see cref="FrameType"/> property equals <see cref="RenderTreeFrameType.NamedEvent"/>,
+    /// gets the assigned name. Otherwise, the value is undefined.
+    /// </summary>
+    public string NamedEventAssignedName => NamedEventAssignedNameField;
+
     // Element constructor
     private RenderTreeFrame(int sequence, int elementSubtreeLength, string elementName, object elementKey)
         : this()
@@ -395,6 +414,12 @@ internal static RenderTreeFrame ElementReferenceCapture(int sequence, Action<Ele
     internal static RenderTreeFrame ComponentReferenceCapture(int sequence, Action<object> componentReferenceCaptureAction, int parentFrameIndex)
         => new RenderTreeFrame(sequence, componentReferenceCaptureAction: componentReferenceCaptureAction, parentFrameIndex: parentFrameIndex);
 
+    internal static RenderTreeFrame NamedEvent(int sequence, string eventType, string assignedName)
+        => new RenderTreeFrame { SequenceField = sequence, FrameTypeField = RenderTreeFrameType.NamedEvent, NamedEventTypeField = eventType, NamedEventAssignedNameField = assignedName };
+
+    internal static RenderTreeFrame ComponentRenderModeFrame(int sequence, IComponentRenderMode renderMode)
+        => new RenderTreeFrame { SequenceField = sequence, FrameTypeField = RenderTreeFrameType.ComponentRenderMode, ComponentRenderModeField = renderMode };
+
     internal RenderTreeFrame WithElementSubtreeLength(int elementSubtreeLength)
         => new RenderTreeFrame(SequenceField, elementSubtreeLength: elementSubtreeLength, ElementNameField, ElementKeyField);
 

src/Components/Components/src/RenderTree/RenderTreeFrameArrayBuilder.cs

@@ -149,4 +149,20 @@ public void AppendComponentRenderMode(int sequence, IComponentRenderMode renderM
             ComponentRenderModeField = renderMode,
         };
     }
+
+    public void AppendNamedEvent(int sequence, string eventType, string assignedName)
+    {
+        if (_itemsInUse == _items.Length)
+        {
+            GrowBuffer(_items.Length * 2);
+        }
+
+        _items[_itemsInUse++] = new RenderTreeFrame
+        {
+            SequenceField = sequence,
+            FrameTypeField = RenderTreeFrameType.NamedEvent,
+            NamedEventTypeField = eventType,
+            NamedEventAssignedNameField = assignedName,
+        };
+    }
 }

src/Components/Components/src/RenderTree/RenderTreeFrameType.cs

@@ -63,4 +63,9 @@ public enum RenderTreeFrameType : short
     /// Represents an instruction to use a specified render mode for the component.
     /// </summary>
     ComponentRenderMode = 9,
+
+    /// <summary>
+    /// Represents an application-assigned name for an event.
+    /// </summary>
+    NamedEvent = 10,
 }

src/Components/Components/src/RenderTree/Renderer.cs

@@ -636,22 +636,6 @@ internal void TrackReplacedEventHandlerId(ulong oldEventHandlerId, ulong newEven
         _eventHandlerIdReplacements.Add(oldEventHandlerId, newEventHandlerId);
     }
 
-    /// <summary>
-    /// Tracks named events defined during rendering.
-    /// </summary>
-    /// <param name="eventHandlerId">The event handler ID associated with the named event.</param>
-    /// <param name="componentId">The component ID defining the name.</param>
-    /// <param name="eventHandlerName">The event name.</param>
-    protected internal virtual void TrackNamedEventId(ulong eventHandlerId, int componentId, string eventHandlerName)
-    {
-    }
-
-    /// <summary>
-    /// Indicates whether named event handlers should be tracked.
-    /// </summary>
-    /// <returns><c>true</c> if named event handlers should be tracked; <c>false</c> otherwise.</returns>
-    protected internal virtual bool ShouldTrackNamedEventHandlers() => false;
-
     private EventCallback GetRequiredEventCallback(ulong eventHandlerId)
     {
         if (!_eventBindings.TryGetValue(eventHandlerId, out var callback))