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[release/10.0] [Blazor] Disable preloading for enhanced navigation #63546

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Merged
merged 2 commits into from
Sep 11, 2025
Merged

[release/10.0] [Blazor] Disable preloading for enhanced navigation #63546

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043c5aa
Compare preload attributes
maraf Sep 4, 2025
13f4a00
Disable preloading for enhanced navigation
maraf Sep 4, 2025
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2 changes: 1 addition & 1 deletion src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.Streaming.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
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5 changes: 5 additions & 0 deletions src/Components/Endpoints/src/Rendering/SSRRenderModeBoundary.cs
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Expand Up @@ -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))
{
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9 changes: 0 additions & 9 deletions src/Components/Web.JS/src/Rendering/DomMerging/DomSync.ts
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Expand Up @@ -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
Expand All @@ -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[];
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