Disable preloading for enhanced navigation

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/AttributeSync.ts

@@ -43,7 +43,7 @@ export function synchronizeAttributes(destination: Element, source: Element) {
   }
 }
 
-export function attributeSetsAreIdentical(destAttrs: NamedNodeMap, sourceAttrs: NamedNodeMap): boolean {
+function attributeSetsAreIdentical(destAttrs: NamedNodeMap, sourceAttrs: NamedNodeMap): boolean {
   const destAttrsLength = destAttrs.length;
   if (destAttrsLength !== sourceAttrs.length) {
     return false;

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

@@ -5,7 +5,7 @@ import { AutoComponentDescriptor, ComponentDescriptor, ServerComponentDescriptor
 import { isInteractiveRootComponentElement } from '../BrowserRenderer';
 import { applyAnyDeferredValue } from '../DomSpecialPropertyUtil';
 import { LogicalElement, getLogicalChildrenArray, getLogicalNextSibling, getLogicalParent, getLogicalRootDescriptor, insertLogicalChild, insertLogicalChildBefore, isLogicalElement, toLogicalElement, toLogicalRootCommentElement } from '../LogicalElements';
-import { attributeSetsAreIdentical, synchronizeAttributes } from './AttributeSync';
+import { synchronizeAttributes } from './AttributeSync';
 import { cannotMergeDueToDataPermanentAttributes, isDataPermanentElement } from './DataPermanentElementSync';
 import { UpdateCost, ItemList, Operation, computeEditScript } from './EditScript';
 
@@ -308,18 +308,6 @@ function domNodeComparer(a: Node, b: Node): UpdateCost {
         return UpdateCost.Infinite;
       }
 
-      // If both elements are the same preload (based on all attributes), we need to match them and do nothing;
-      // Otherwise, browser would trigger a new preload request.
-      // If attributes don't match, we can't simply update the element, because browser could trigger
-      // an invalid preload request based on attribute order.
-      const aIsPreload = isPreloadElement(a as Element);
-      const bIsPreload = isPreloadElement(b as Element);
-      if (aIsPreload && bIsPreload && attributeSetsAreIdentical((a as Element).attributes, (b as Element).attributes)) {
-        return UpdateCost.None;
-      } else if (aIsPreload || bIsPreload) {
-        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
@@ -331,10 +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[];