[Blazor] Disable preloading for enhanced navigation (#63544)

Author: maraf

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.Streaming.cs

@@ -324,7 +324,7 @@ private void WriteComponentHtml(int componentId, TextWriter output, bool allowBo
  }
  }
 
- private static bool IsProgressivelyEnhancedNavigation(HttpRequest request)
+ internal static bool IsProgressivelyEnhancedNavigation(HttpRequest request)
  {
  // For enhanced nav, the Blazor JS code controls the "accept" header precisely, so we can be very specific about the format
  var accept = request.Headers.Accept;

src/Components/Endpoints/src/Rendering/SSRRenderModeBoundary.cs

@@ -124,6 +124,11 @@ public Task SetParametersAsync(ParameterView parameters)
 
  private void PreloadWebAssemblyAssets()
  {
+ if (EndpointHtmlRenderer.IsProgressivelyEnhancedNavigation(_httpContext.Request))
+ {
+ return;
+ }
+
  var preloads = _httpContext.GetEndpoint()?.Metadata.GetMetadata<ResourcePreloadCollection>();
  if (preloads != null && preloads.TryGetAssets("webassembly", out var preloadAssets))
  {

src/Components/Web.JS/src/Rendering/DomMerging/DomSync.ts

@@ -308,11 +308,6 @@ function domNodeComparer(a: Node, b: Node): UpdateCost {
  return UpdateCost.Infinite;
  }
 
- // Always treat "preloads" as new elements.
- if (isPreloadElement(a as Element) || isPreloadElement(b as Element)) {
- return UpdateCost.Infinite;
- }
-
  return UpdateCost.None;
  case Node.DOCUMENT_TYPE_NODE:
  // It's invalid to insert or delete doctype, and we have no use case for doing that. So just skip such
@@ -324,10 +319,6 @@ function domNodeComparer(a: Node, b: Node): UpdateCost {
  }
 }
 
-function isPreloadElement(el: Element): boolean {
- return el.tagName === 'LINK' && el.attributes.getNamedItem('rel')?.value === 'preload';
-}
-
 function upgradeComponentCommentsToLogicalRootComments(root: Node): ComponentDescriptor[] {
  const serverDescriptors = discoverComponents(root, 'server') as ServerComponentDescriptor[];
  const webAssemblyDescriptors = discoverComponents(root, 'webassembly') as WebAssemblyComponentDescriptor[];