Handle another case in temporary API

Author: SteveSandersonMS

src/Components/Components/src/Rendering/RenderTreeBuilder.cs

@@ -45,6 +45,8 @@ public sealed class RenderTreeBuilder : IDisposable
     /// <param name="elementName">A value representing the type of the element.</param>
     public void OpenElement(int sequence, string elementName)
     {
+        CompletePendingNamedSubmitEvent();
+
         // We are entering a new scope, since we track the "duplicate attributes" per
         // element/component we might need to clean them up now.
         if (_hasSeenAddMultipleAttributes)
@@ -64,11 +66,7 @@ public void OpenElement(int sequence, string elementName)
     /// </summary>
     public void CloseElement()
     {
-        if (_pendingNamedSubmitEvent is { } pendingNamedSubmitEvent)
-        {
-            AddNamedEvent(pendingNamedSubmitEvent.Sequence, "onsubmit", pendingNamedSubmitEvent.AssignedName);
-            _pendingNamedSubmitEvent = default;
-        }
+        CompletePendingNamedSubmitEvent();
 
         var indexOfEntryBeingClosed = _openElementIndices.Pop();
 
@@ -82,6 +80,16 @@ public void CloseElement()
         _entries.Buffer[indexOfEntryBeingClosed].ElementSubtreeLengthField = _entries.Count - indexOfEntryBeingClosed;
     }
 
+    // TODO: Remove this once Razor supports @onsubmit:name
+    private void CompletePendingNamedSubmitEvent()
+    {
+        if (_pendingNamedSubmitEvent is { } pendingNamedSubmitEvent)
+        {
+            AddNamedEvent(pendingNamedSubmitEvent.Sequence, "onsubmit", pendingNamedSubmitEvent.AssignedName);
+            _pendingNamedSubmitEvent = default;
+        }
+    }
+
     /// <summary>
     /// Appends a frame representing markup content.
     /// </summary>
@@ -592,6 +600,8 @@ public void SetKey(object? value)
 
     private void OpenComponentUnchecked(int sequence, [DynamicallyAccessedMembers(Component)] Type componentType)
     {
+        CompletePendingNamedSubmitEvent();
+
         // We are entering a new scope, since we track the "duplicate attributes" per
         // element/component we might need to clean them up now.
         if (_hasSeenAddMultipleAttributes)

src/Components/Components/test/Rendering/RenderTreeBuilderTest.cs

@@ -2300,15 +2300,18 @@ public void TemporaryApiForNamedSubmitEventsWorksEvenIfAttributesAddedAfter()
         builder.AddAttribute(1, "attr1", 123);
         builder.AddAttribute(2, "@onsubmit:name", "some custom name");
         builder.AddAttribute(3, "attr2", 456);
+        builder.OpenElement(4, "other");
+        builder.CloseElement();
         builder.CloseElement();
 
         // Assert
         Assert.Collection(
             builder.GetFrames().AsEnumerable(),
-            frame => AssertFrame.Element(frame, "div", 4, 0),
+            frame => AssertFrame.Element(frame, "div", 5, 0),
             frame => AssertFrame.Attribute(frame, "attr1", "123", 1),
             frame => AssertFrame.Attribute(frame, "attr2", "456", 3),
-            frame => AssertFrame.NamedEvent(frame, "onsubmit", "some custom name", 2));
+            frame => AssertFrame.NamedEvent(frame, "onsubmit", "some custom name", 2),
+            frame => AssertFrame.Element(frame, "other", 1));
     }
 
     private class TestComponent : IComponent