Remove temporary APIs now Razor compiler is updated (#51252)

# Remove temporary APIs now Razor compiler is updated

The Razor Compiler now supports `@rendermode` and `@formname` natively, so use that.

## Description

While waiting for the Razor Compiler's native support for `@rendermode` and `@formname`, we had some temporary APIs. They are less nice to use and don't perform as well. We have always planned to remove them by the time .NET 8 ships. This PR actually removes them and switches all the tests and templates over to the new native syntax.

Since this PR is changing the project template anyway, it also implements the "remove unnecessary top-level Components folder in wasm template" (#51167)

Fixes #50225
Fixes #51167

## Customer Impact

We have to remove these APIs because otherwise they end up having to be supported forever (or at least, years), and (1) they are now unnecessary and ugly, and (2) they harm perf even if you're not using them, because the way they work requires the renderer to keep checking whether you just used them.

## Regression?

- [ ] Yes
- [x] No

[If yes, specify the version the behavior has regressed from]

## Risk

- [ ] High
- [x] Medium
- [ ] Low

It's a meaningful change to the syntax that also involves some template changes. However we always planned to make this change, and couldn't have done it earlier because the compiler changes were not available until now.

Also we are still waiting for a build of VS that includes the necessary change, so until then, VS will show red squigglies for the new syntax (though it still compiles and runs successfully).

## Verification

- [x] Manual (required)
- [x] Automated

## Packaging changes reviewed?

- [ ] Yes
- [ ] No
- [x] N/A

Author: SteveSandersonMS

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

@@ -26,7 +26,6 @@ Microsoft.AspNetCore.Components.RenderHandle.DispatchExceptionAsync(System.Excep
 *REMOVED*Microsoft.AspNetCore.Components.NavigationManager.ToAbsoluteUri(string! relativeUri) -> System.Uri!
 Microsoft.AspNetCore.Components.NavigationManager.ToAbsoluteUri(string? relativeUri) -> System.Uri!
 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
 *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.AddComponentRenderMode(Microsoft.AspNetCore.Components.IComponentRenderMode! renderMode) -> void

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

@@ -27,8 +27,6 @@ public sealed class RenderTreeBuilder : IDisposable
     private RenderTreeFrameType? _lastNonAttributeFrameType;
     private bool _hasSeenAddMultipleAttributes;
     private Dictionary<string, int>? _seenAttributeNames;
-    private IComponentRenderMode? _pendingComponentCallSiteRenderMode; // TODO: Remove when Razor compiler supports call-site @rendermode
-    private string? _pendingNamedSubmitEvent; // TODO: Remove when Razor compiler supports @formname
 
     /// <summary>
     /// The reserved parameter name used for supplying child content.
@@ -45,8 +43,6 @@ 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)
@@ -66,8 +62,6 @@ public void OpenElement(int sequence, string elementName)
     /// </summary>
     public void CloseElement()
     {
-        CompletePendingNamedSubmitEvent();
-
         var indexOfEntryBeingClosed = _openElementIndices.Pop();
 
         // We might be closing an element with only attributes, run the duplicate cleanup pass
@@ -80,16 +74,6 @@ public void CloseElement()
         _entries.Buffer[indexOfEntryBeingClosed].ElementSubtreeLengthField = _entries.Count - indexOfEntryBeingClosed;
     }
 
-    // TODO: Remove this once Razor supports @formname
-    private void CompletePendingNamedSubmitEvent()
-    {
-        if (_pendingNamedSubmitEvent is not null)
-        {
-            AddNamedEvent("onsubmit", _pendingNamedSubmitEvent);
-            _pendingNamedSubmitEvent = default;
-        }
-    }
-
     /// <summary>
     /// Appends a frame representing markup content.
     /// </summary>
@@ -237,16 +221,7 @@ public void AddAttribute(int sequence, string name, string? value)
         AssertCanAddAttribute();
         if (value != null || _lastNonAttributeFrameType == RenderTreeFrameType.Component)
         {
-            // TODO: Remove this once the Razor compiler is updated to support @formname
-            // That should compile directly as a call to AddNamedEvent.
-            if (string.Equals(name, "@formname", StringComparison.Ordinal) && _lastNonAttributeFrameType == RenderTreeFrameType.Element)
-            {
-                _pendingNamedSubmitEvent = value!;
-            }
-            else
-            {
-                _entries.AppendAttribute(sequence, name, value);
-            }
+            _entries.AppendAttribute(sequence, name, value);
         }
         else
         {
@@ -530,28 +505,6 @@ public void OpenComponent(int sequence, [DynamicallyAccessedMembers(Component)]
         OpenComponentUnchecked(sequence, componentType);
     }
 
-    /// <summary>
-    /// Temporary API until Razor compiler is updated. This will be removed before .NET 8 ships.
-    /// </summary>
-    public void AddComponentParameter(int sequence, string name, IComponentRenderMode renderMode)
-    {
-        if (string.Equals(name, "@rendermode", StringComparison.Ordinal))
-        {
-            // When the Razor compiler is updated, <SomeComponent @rendermode="@RenderMode.WebAssembly" />  would compile directly as a call
-            // to AddComponentRenderMode(RenderMode.WebAssembly), which must appear after all attributes. Until then we'll intercept regular
-            // parameters with this name and IComponentRenderMode values. Unfortunately we can't guarantee that the parameter will appear after
-            // all other parameters (e.g., ChildContent would always go later), so use this inefficient trick to defer adding it.
-            // It won't be needed once the Razor compiler supports @rendermode.
-            _pendingComponentCallSiteRenderMode = renderMode;
-        }
-        else
-        {
-            // For other parameter names, the developer is doing something custom so just pass the parameter as normal
-            // This special case will also not be relevant once we have @rendermode
-            AddComponentParameter(sequence, name, (object)renderMode);
-        }
-    }
-
     /// <summary>
     /// Appends a frame representing a component parameter.
     /// </summary>
@@ -600,8 +553,6 @@ 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)
@@ -621,12 +572,6 @@ private void OpenComponentUnchecked(int sequence, [DynamicallyAccessedMembers(Co
     /// </summary>
     public void CloseComponent()
     {
-        if (_pendingComponentCallSiteRenderMode is not null)
-        {
-            AddComponentRenderMode(_pendingComponentCallSiteRenderMode);
-            _pendingComponentCallSiteRenderMode = null;
-        }
-
         var indexOfEntryBeingClosed = _openElementIndices.Pop();
 
         // We might be closing a component with only attributes. Run the attribute cleanup pass

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

@@ -2171,39 +2171,6 @@ public void CannotAddParametersAfterComponentRenderMode()
         Assert.Equal($"Component parameters may only be added immediately after frames of type {RenderTreeFrameType.Component}", ex.Message);
     }
 
-    [Fact]
-    public void TemporaryApiForCallSiteComponentRenderModeWorksEvenIfOtherParameterAddedAfter()
-    {
-        // For the temporary syntax rendermode=@something (as opposed to @rendermode=@something), we can't guarantee
-        // the Razor compiler will emit the AddComponentParameter call for rendermode last. For example if there's a
-        // ChildContent it will actually emit that last. So for the temporary syntax to be usable it has to support
-        // other component parameters being added afterwards, even though that does not need to be supported for
-        // AddComponentRenderMode (since the compiler can be sure to add that after all component parameters).
-
-        // Arrange
-        var builder = new RenderTreeBuilder();
-        var renderMode = new TestRenderMode();
-
-        // Act
-        builder.OpenComponent<TestComponent>(0);
-        builder.AddComponentParameter(1, "param", 123);
-        builder.AddComponentParameter(2, "@rendermode", renderMode);
-        builder.AddComponentParameter(3, "anotherparam", 456);
-        builder.CloseComponent();
-
-        // Assert
-        Assert.Collection(
-            builder.GetFrames().AsEnumerable(),
-            frame =>
-            {
-                AssertFrame.Component<TestComponent>(frame, 4, 0);
-                Assert.True(frame.ComponentFrameFlags.HasFlag(ComponentFrameFlags.HasCallerSpecifiedRenderMode));
-            },
-            frame => AssertFrame.Attribute(frame, "param", 123, 1),
-            frame => AssertFrame.Attribute(frame, "anotherparam", 456, 3),
-            frame => AssertFrame.ComponentRenderMode(frame, renderMode));
-    }
-
     [Fact]
     public void CanAddNamedEvent()
     {
@@ -2301,34 +2268,6 @@ public void CannotAddAttributesAfterNamedEvent()
         Assert.Equal($"Attributes may only be added immediately after frames of type {RenderTreeFrameType.Element} or {RenderTreeFrameType.Component}", ex.Message);
     }
 
-    [Fact]
-    public void TemporaryApiForFormNameEventsWorksEvenIfAttributesAddedAfter()
-    {
-        // TODO: Remove this once the Razor compiler is updated to support @formname directly
-
-        // Arrange
-        var builder = new RenderTreeBuilder();
-        var renderMode = new TestRenderMode();
-
-        // Act
-        builder.OpenElement(0, "div");
-        builder.AddAttribute(1, "attr1", 123);
-        builder.AddAttribute(2, "@formname", "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", 5, 0),
-            frame => AssertFrame.Attribute(frame, "attr1", "123", 1),
-            frame => AssertFrame.Attribute(frame, "attr2", "456", 3),
-            frame => AssertFrame.NamedEvent(frame, "onsubmit", "some custom name"),
-            frame => AssertFrame.Element(frame, "other", 1));
-    }
-
     private class TestComponent : IComponent
     {
         public void Attach(RenderHandle renderHandle) { }

src/Components/Endpoints/test/HotReloadServiceTests.cs

@@ -195,7 +195,7 @@ private static RazorComponentEndpointDataSource<TComponent> CreateDataSource<TCo
 
     private class StaticComponent : ComponentBase { }
 
-    [RenderModeInteractiveServer]
+    [TestRenderMode<InteractiveServerRenderMode>]
     private class ServerComponent : ComponentBase { }
 
     private class MockEndpointProvider : RenderModeEndpointProvider

src/Components/Endpoints/test/RazorComponentEndpointDataSourceTest.cs

@@ -5,6 +5,7 @@
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Components.Discovery;
 using Microsoft.AspNetCore.Components.Endpoints.Infrastructure;
+using Microsoft.AspNetCore.Components.Endpoints.Tests;
 using Microsoft.AspNetCore.Components.Web;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Patterns;
@@ -242,13 +243,13 @@ private RazorComponentEndpointDataSource<TComponent> CreateDataSource<TComponent
         return result;
     }
 
-    [RenderModeInteractiveServer]
+    [TestRenderMode<InteractiveServerRenderMode>]
     private class ServerComponent : ComponentBase { }
 
-    [RenderModeInteractiveAuto]
+    [TestRenderMode<InteractiveAutoRenderMode>]
     private class AutoComponent : ComponentBase { }
 
-    [RenderModeInteractiveWebAssembly]
+    [TestRenderMode<InteractiveWebAssemblyRenderMode>]
     private class WebAssemblyComponent : ComponentBase { }
 
     private class ServerEndpointProvider : RenderModeEndpointProvider

src/Components/Endpoints/test/TestComponents/InteractiveGreetingServer.razor

@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Web
-@attribute [RenderModeInteractiveServer]
+@rendermode RenderMode.InteractiveServer
 
 <p>Hello @(Name ?? "(null)")!</p>
 

src/Components/Endpoints/test/TestComponents/InteractiveGreetingServerNonPrerendered.razor

@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Web
-@attribute [RenderModeInteractiveServer(false)]
+@rendermode @(new InteractiveServerRenderMode(prerender: false))
 
 <p>Hello @(Name ?? "(null)")!</p>
 

src/Components/Endpoints/test/TestComponents/InteractiveGreetingWebAssembly.razor

@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Web
-@attribute [RenderModeInteractiveWebAssembly]
+@rendermode RenderMode.InteractiveWebAssembly
 
 <p>Hello @(Name ?? "(null)")!</p>
 

src/Components/Endpoints/test/TestComponents/InteractiveGreetingWebAssemblyNonPrerendered.razor

@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Web
-@attribute [RenderModeInteractiveWebAssembly(false)]
+@rendermode @(new InteractiveWebAssemblyRenderMode(prerender: false))
 
 <p>Hello @(Name ?? "(null)")!</p>
 

src/Components/Endpoints/test/TestComponents/InteractiveWithInteractiveChild.razor

@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Web
-@attribute [RenderModeInteractiveWebAssembly]
+@rendermode RenderMode.InteractiveWebAssembly
 
 <h1>This is @nameof(InteractiveWithInteractiveChild)</h1>