[Blazor] Generate better error message(s) when we encounter an unknown RenderTreeFrameType (#63230)

Print the component path and the sequence of RenderTreeFrames up to the current frame for better diagnostics.

Author: Copilot

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

@@ -746,10 +746,50 @@ private static void AppendDiffEntriesForFramesWithSameSequence(
             // We don't handle attributes here, they have their own diff logic.
             // See AppendDiffEntriesForAttributeFrame
             default:
-                throw new NotImplementedException($"Encountered unsupported frame type during diffing: {newTree[newFrameIndex].FrameTypeField}");
+                throw new NotImplementedException(CreateDiffErrorMessage(ref diffContext, newFrameIndex));
         }
     }
 
+    private static string CreateDiffErrorMessage(ref DiffContext diffContext, int newFrameIndex)
+    {
+        var newTree = diffContext.NewTree;
+        var unsupportedFrameType = newTree[newFrameIndex].FrameTypeField;
+        
+        // Build component hierarchy path
+        var componentPath = BuildComponentPath(diffContext.Renderer, diffContext.ComponentId);
+        
+        // Build frame types descriptor
+        var frameTypesDescriptor = BuildFrameTypeDescriptor(newTree, newFrameIndex);
+        
+        return $"Encountered an unsupported frame type during diffing {unsupportedFrameType} for Component Path: '{componentPath}' on tree with length '{newTree.Length}' and contents '{frameTypesDescriptor}'.";
+    }
+
+    private static string BuildFrameTypeDescriptor(RenderTreeFrame[] renderTree, int frameIndex)
+    {
+        var frameTypes = new List<string>();
+        for (var i = 0; i <= frameIndex && i < renderTree.Length; i++)
+        {
+            frameTypes.Add(renderTree[i].FrameTypeField.ToString());
+        }
+        
+        return string.Join(", ", frameTypes);
+    }
+
+    private static string BuildComponentPath(Renderer renderer, int componentId)
+    {
+        var componentPath = new List<string>();
+        var currentComponentState = renderer.GetRequiredComponentState(componentId);
+        
+        while (currentComponentState is not null)
+        {
+            var componentType = currentComponentState.Component.GetType();
+            componentPath.Insert(0, componentType.Name);
+            currentComponentState = currentComponentState.ParentComponentState;
+        }
+        
+        return string.Join(" -> ", componentPath);
+    }
+
     // This should only be called for attributes that have the same name. This is an
     // invariant maintained by the callers.
     private static void AppendDiffEntriesForAttributeFrame(

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

@@ -758,7 +758,7 @@ private ulong FindLatestEventHandlerIdInChain(ulong eventHandlerId)
         return eventHandlerId;
     }
 
-    private ComponentState GetRequiredComponentState(int componentId)
+    internal ComponentState GetRequiredComponentState(int componentId)
         => _componentStateById.TryGetValue(componentId, out var componentState)
             ? componentState
             : throw new ArgumentException($"The renderer does not have a component with ID {componentId}.");