Optimize lazy load navigation

src/Elastic.ApiExplorer/ApiViewModel.cs

@@ -37,6 +37,7 @@ public GlobalLayoutViewModel CreateGlobalLayoutModel() =>
 			Previous = null,
 			Next = null,
 			NavigationHtml = NavigationHtml,
+			NavigationFileName = string.Empty,
 			UrlPathPrefix = BuildContext.UrlPathPrefix,
 			AllowIndexing = BuildContext.AllowIndexing,
 			CanonicalBaseUrl = BuildContext.CanonicalBaseUrl,

src/Elastic.ApiExplorer/OpenApiGenerator.cs

@@ -292,7 +292,12 @@ private async Task<IFileInfo> Render<T>(INavigationItem current, T page, ApiRend
 		renderContext = renderContext with
 		{
 			CurrentNavigation = current,
-			NavigationHtml = navigationHtml
+			NavigationHtml = navigationHtml switch
+			{
+				EmptyNavigationRenderResult => string.Empty,
+				OkNavigationRenderResult result => result.Html,
+				_ => throw new Exception("Unexpected navigation render result")
+			}
 		};
 		await using var stream = _writeFileSystem.FileStream.New(outputFile.FullName, FileMode.OpenOrCreate);
 		await page.RenderAsync(stream, renderContext, ctx);

src/Elastic.Documentation.Site/Assets/main.ts

@@ -15,15 +15,23 @@ import { $, $$ } from 'select-dom'
 import { UAParser } from 'ua-parser-js'
 
 const { getOS } = new UAParser()
+const isLazyLoadNavigationEnabled =
+    $('meta[property="docs:feature:lazy-load-navigation"]')?.content === 'true'
 
 document.addEventListener('htmx:load', function (event) {
-    console.log('htmx:load')
-    console.log(event.detail)
     initTocNav()
     initHighlight()
     initCopyButton()
     initTabs()
-    initNav()
+
+    // We do this so that the navigation is not initialized twice
+    if (isLazyLoadNavigationEnabled) {
+        if (event.detail.elt.id === 'nav-tree') {
+            initNav()
+        }
+    } else {
+        initNav()
+    }
     initSmoothScroll()
     openDetailsWithAnchor()
     initDismissibleBanner()

src/Elastic.Documentation.Site/Layout/_Head.cshtml

@@ -34,3 +34,4 @@
 	{
 		<meta property="og:url" content="@Model.CanonicalUrl" />
 	}
+	<meta property="docs:feature:lazy-load-navigation" content="@Model.Features.LazyLoadNavigation" />

src/Elastic.Documentation.Site/Layout/_PagesNav.cshtml

@@ -1,9 +1,9 @@
 @inherits RazorSlice<Elastic.Documentation.Site.GlobalLayoutViewModel>
 <aside class="sidebar bg-white fixed md:sticky shadow-2xl md:shadow-none left-[100%] group-has-[#pages-nav-hamburger:checked]/body:left-0 bottom-0 md:left-auto pl-6 md:pl-2 top-[calc(var(--offset-top)+1px)] w-[80%] md:w-auto shrink-0 border-r-1 border-r-grey-20 z-40 md:z-auto">
 
-	@if (Model.Features.LazyLoadNavigation)
+	@if (Model.Features.LazyLoadNavigation && !string.IsNullOrEmpty(Model.NavigationFileName))
 	{
-		<div hx-get="@(Model.CurrentNavigationItem.Url + (Model.CurrentNavigationItem.Url.EndsWith('/') ? "index.nav.html" : "/index.nav.html"))" hx-trigger="load" hx-params="nav" hx-push-url="false" hx-swap="innerHTML" hx-target="#pages-nav"></div>
+		<div class="hidden" hx-get="@(Model.Link(Model.NavigationFileName))" hx-trigger="load" hx-params="nav" hx-push-url="false" hx-swap="innerHTML" hx-target="#pages-nav"></div>
 	}
 	<nav
 		id="pages-nav"

src/Elastic.Documentation.Site/Navigation/INavigationHtmlWriter.cs

@@ -10,11 +10,30 @@ public interface INavigationHtmlWriter
 {
 	const int AllLevels = -1;
 
-	Task<string> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation, Uri navigationSource, int maxLevel, Cancel ctx = default);
+	Task<INavigationRenderResult> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation, Uri navigationSource,
+		int maxLevel, Cancel ctx = default);
 
 	async Task<string> Render(NavigationViewModel model, Cancel ctx)
 	{
 		var slice = _TocTree.Create(model);
 		return await slice.RenderAsync(cancellationToken: ctx);
 	}
 }
+
+public interface INavigationRenderResult
+{
+	string Html { get; init; }
+	string Id { get; init; }
+}
+
+public record OkNavigationRenderResult : INavigationRenderResult
+{
+	public required string Html { get; init; }
+	public required string Id { get; init; }
+}
+
+public record EmptyNavigationRenderResult : INavigationRenderResult
+{
+	public string Html { get; init; } = string.Empty;
+	public string Id { get; init; } = string.Empty;
+}

src/Elastic.Documentation.Site/Navigation/IsolatedBuildNavigationHtmlWriter.cs

@@ -4,6 +4,7 @@
 
 using System.Collections.Concurrent;
 using Elastic.Documentation.Configuration;
+using Elastic.Documentation.Extensions;
 
 namespace Elastic.Documentation.Site.Navigation;
 
@@ -12,19 +13,30 @@ public class IsolatedBuildNavigationHtmlWriter(BuildContext context, IRootNaviga
 {
 	private readonly ConcurrentDictionary<(string, int), string> _renderedNavigationCache = [];
 
-	public async Task<string> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation, Uri navigationSource, int maxLevel, Cancel ctx = default)
+	public async Task<INavigationRenderResult> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation,
+		Uri navigationSource, int maxLevel, Cancel ctx = default)
 	{
 		var navigation = context.Configuration.Features.PrimaryNavEnabled || currentRootNavigation.IsUsingNavigationDropdown
 			? currentRootNavigation
 			: siteRoot;
 
+		var id = ShortId.Create($"{(navigation.Id, maxLevel).GetHashCode()}");
+
 		if (_renderedNavigationCache.TryGetValue((navigation.Id, maxLevel), out var value))
-			return value;
+			return new OkNavigationRenderResult
+			{
+				Html = value,
+				Id = id
+			};
 
 		var model = CreateNavigationModel(navigation, maxLevel);
 		value = await ((INavigationHtmlWriter)this).Render(model, ctx);
 		_renderedNavigationCache[(navigation.Id, maxLevel)] = value;
-		return value;
+		return new OkNavigationRenderResult
+		{
+			Html = value,
+			Id = id
+		};
 	}
 
 	private NavigationViewModel CreateNavigationModel(IRootNavigationItem<INavigationModel, INavigationItem> navigation, int maxLevel) =>

src/Elastic.Documentation.Site/Navigation/_TocTree.cshtml

@@ -1,7 +1,7 @@
 @using Elastic.Documentation.Site.Navigation
 @inherits RazorSlice<Elastic.Documentation.Site.Navigation.NavigationViewModel>
 
-<div class="pb-20 font-body">
+<div class="pb-20 font-body" id="nav-tree">
 	@{
 		var currentTopLevelItem = Model.TopLevelItems.FirstOrDefault(i => i.Id == Model.Tree.Id) ?? Model.Tree;
 	} 

src/Elastic.Documentation.Site/_ViewModels.cs

@@ -27,6 +27,7 @@ public record GlobalLayoutViewModel
 	public required INavigationItem? Next { get; init; }
 
 	public required string NavigationHtml { get; init; }
+	public required string NavigationFileName { get; init; }
 	public required string? UrlPathPrefix { get; init; }
 	public required Uri? CanonicalBaseUrl { get; init; }
 	public string? CanonicalUrl => CanonicalBaseUrl is not null ?

src/Elastic.Markdown/Exporters/DocumentationFileExporter.cs

@@ -66,7 +66,7 @@ public class DocumentationFileExporter(IFileSystem readFileSystem, IFileSystem w
 	public override async ValueTask ProcessFile(ProcessingFileContext context, Cancel ctx)
 	{
 		if (context.File is MarkdownFile markdown)
-			context.MarkdownDocument = await context.HtmlWriter.WriteAsync(context.OutputFile, markdown, context.ConversionCollector, ctx);
+			context.MarkdownDocument = await context.HtmlWriter.WriteAsync(context.BuildContext.DocumentationOutputDirectory, context.OutputFile, markdown, context.ConversionCollector, ctx);
 		else
 		{
 			if (context.OutputFile.Directory is { Exists: false })

src/Elastic.Markdown/Extensions/DetectionRules/RuleDocumentationFileExporter.cs

@@ -21,10 +21,10 @@ public override async ValueTask ProcessFile(ProcessingFileContext context, Cance
 		switch (context.File)
 		{
 			case DetectionRuleFile df:
-				context.MarkdownDocument = await htmlWriter.WriteAsync(DetectionRuleFile.OutputPath(outputFile, context.BuildContext), df, conversionCollector, ctx);
+				context.MarkdownDocument = await htmlWriter.WriteAsync(context.BuildContext.DocumentationOutputDirectory, DetectionRuleFile.OutputPath(outputFile, context.BuildContext), df, conversionCollector, ctx);
 				break;
 			case MarkdownFile markdown:
-				context.MarkdownDocument = await htmlWriter.WriteAsync(outputFile, markdown, conversionCollector, ctx);
+				context.MarkdownDocument = await htmlWriter.WriteAsync(context.BuildContext.DocumentationOutputDirectory, outputFile, markdown, conversionCollector, ctx);
 				break;
 			default:
 				if (outputFile.Directory is { Exists: false })

src/Elastic.Markdown/HtmlWriter.cs

@@ -5,6 +5,7 @@
 using System.IO.Abstractions;
 using Elastic.Documentation;
 using Elastic.Documentation.Configuration.Builder;
+using Elastic.Documentation.Extensions;
 using Elastic.Documentation.Legacy;
 using Elastic.Documentation.Site.FileProviders;
 using Elastic.Documentation.Site.Navigation;
@@ -55,10 +56,14 @@ private async Task<RenderResult> RenderLayout(MarkdownFile markdown, MarkdownDoc
 		var html = MarkdownFile.CreateHtml(document);
 		await DocumentationSet.Tree.Resolve(ctx);
 
-		var fullNavigationHtml = await NavigationHtmlWriter.RenderNavigation(markdown.NavigationRoot, markdown.NavigationSource, INavigationHtmlWriter.AllLevels, ctx);
-		var miniNavigationHtml = DocumentationSet.Context.Configuration.Features.LazyLoadNavigation
+		var fullNavigationRenderResult = await NavigationHtmlWriter.RenderNavigation(markdown.NavigationRoot, markdown.NavigationSource, INavigationHtmlWriter.AllLevels, ctx);
+		var miniNavigationRenderResult = DocumentationSet.Context.Configuration.Features.LazyLoadNavigation
 			? await NavigationHtmlWriter.RenderNavigation(markdown.NavigationRoot, markdown.NavigationSource, 1, ctx)
-			: "lazy navigation feature disabled";
+			: new EmptyNavigationRenderResult();
+
+		var navigationHtmlRenderResult = DocumentationSet.Context.Configuration.Features.LazyLoadNavigation
+			? miniNavigationRenderResult
+			: fullNavigationRenderResult;
 
 		var current = PositionalNavigation.GetCurrent(markdown);
 		var previous = PositionalNavigation.GetPrevious(markdown);
@@ -103,6 +108,15 @@ private async Task<RenderResult> RenderLayout(MarkdownFile markdown, MarkdownDoc
 		if (PositionalNavigation.MarkdownNavigationLookup.TryGetValue("docs-content://versions.md", out var item))
 			allVersionsUrl = item.Url;
 
+
+		var navigationFileName = $"{fullNavigationRenderResult.Id}.nav.html";
+
+		_ = DocumentationSet.NavigationRenderResults.TryAdd(
+			fullNavigationRenderResult.Id,
+			fullNavigationRenderResult
+		);
+
+
 		var slice = Page.Index.Create(new IndexViewModel
 		{
 			SiteName = siteName,
@@ -118,7 +132,8 @@ private async Task<RenderResult> RenderLayout(MarkdownFile markdown, MarkdownDoc
 			PreviousDocument = previous,
 			NextDocument = next,
 			Parents = parents,
-			NavigationHtml = DocumentationSet.Configuration.Features.LazyLoadNavigation ? miniNavigationHtml : fullNavigationHtml,
+			NavigationHtml = navigationHtmlRenderResult.Html,
+			NavigationFileName = navigationFileName,
 			UrlPathPrefix = markdown.UrlPathPrefix,
 			AppliesTo = markdown.YamlFrontMatter?.AppliesTo,
 			GithubEditUrl = editUrl,
@@ -135,15 +150,17 @@ private async Task<RenderResult> RenderLayout(MarkdownFile markdown, MarkdownDoc
 			Products = allProducts,
 			VersionsConfig = DocumentationSet.Context.VersionsConfig
 		});
+
 		return new RenderResult
 		{
 			Html = await slice.RenderAsync(cancellationToken: ctx),
-			FullNavigationPartialHtml = fullNavigationHtml
+			FullNavigationPartialHtml = fullNavigationRenderResult.Html,
+			NavigationFileName = navigationFileName
 		};
 
 	}
 
-	public async Task<MarkdownDocument> WriteAsync(IFileInfo outputFile, MarkdownFile markdown, IConversionCollector? collector, Cancel ctx = default)
+	public async Task<MarkdownDocument> WriteAsync(IDirectoryInfo outBaseDir, IFileInfo outputFile, MarkdownFile markdown, IConversionCollector? collector, Cancel ctx = default)
 	{
 		if (outputFile.Directory is { Exists: false })
 			outputFile.Directory.Create();
@@ -171,10 +188,12 @@ public async Task<MarkdownDocument> WriteAsync(IFileInfo outputFile, MarkdownFil
 		collector?.Collect(markdown, document, rendered.Html);
 		await writeFileSystem.File.WriteAllTextAsync(path, rendered.Html, ctx);
 
-		if (DocumentationSet.Configuration.Features.LazyLoadNavigation)
-		{
-			await writeFileSystem.File.WriteAllTextAsync(path.Replace(".html", ".nav.html"), rendered.FullNavigationPartialHtml, ctx);
-		}
+		if (!DocumentationSet.Configuration.Features.LazyLoadNavigation)
+			return document;
+
+		var navFilePath = Path.Combine(outBaseDir.FullName, rendered.NavigationFileName);
+		if (!writeFileSystem.File.Exists(navFilePath))
+			await writeFileSystem.File.WriteAllTextAsync(navFilePath, rendered.FullNavigationPartialHtml, ctx);
 		return document;
 	}
 
@@ -184,4 +203,6 @@ public record RenderResult
 {
 	public required string Html { get; init; }
 	public required string FullNavigationPartialHtml { get; init; }
+	public required string NavigationFileName { get; init; }
+
 }

src/Elastic.Markdown/IO/DocumentationSet.cs

@@ -2,6 +2,7 @@
 // Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
 // See the LICENSE file in the project root for more information
 
+using System.Collections.Concurrent;
 using System.Collections.Frozen;
 using System.IO.Abstractions;
 using System.Runtime.InteropServices;
@@ -129,6 +130,8 @@ public class DocumentationSet : INavigationLookups, IPositionalNavigation
 
 	public IReadOnlyCollection<IDocsBuilderExtension> EnabledExtensions { get; }
 
+	public ConcurrentDictionary<string, INavigationRenderResult> NavigationRenderResults { get; } = [];
+
 	public DocumentationSet(
 		BuildContext context,
 		ILoggerFactory logger,

src/Elastic.Markdown/Page/Index.cshtml

@@ -26,6 +26,7 @@
 		Next = Model.NextDocument,
 		Parents = Model.Parents,
 		NavigationHtml = Model.NavigationHtml,
+		NavigationFileName = Model.NavigationFileName,
 		UrlPathPrefix = Model.UrlPathPrefix,
 		GithubEditUrl = Model.GithubEditUrl,
 		AllowIndexing = Model.AllowIndexing,

src/Elastic.Markdown/Page/IndexViewModel.cs

@@ -33,6 +33,8 @@ public class IndexViewModel
 	public required INavigationItem[] Parents { get; init; }
 
 	public required string NavigationHtml { get; init; }
+
+	public required string NavigationFileName { get; init; }
 	public required string CurrentVersion { get; init; }
 
 	public required string? AllVersionsUrl { get; init; }

src/tooling/docs-assembler/Navigation/GlobalNavigationHtmlWriter.cs

@@ -5,6 +5,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Immutable;
 using System.Diagnostics.CodeAnalysis;
+using Elastic.Documentation.Extensions;
 using Elastic.Documentation.Site.Navigation;
 using Elastic.Markdown.IO.Navigation;
 
@@ -44,24 +45,29 @@ private bool TryGetNavigationRoot(
 		return true;
 	}
 
-	public async Task<string> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation, Uri navigationSource, int maxLevel = -1, Cancel ctx = default)
+	public async Task<INavigationRenderResult> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation,
+		Uri navigationSource, int maxLevel, Cancel ctx = default)
 	{
-		if (Phantoms.Contains(navigationSource))
-			return string.Empty;
 
-		if (!TryGetNavigationRoot(navigationSource, out var navigationRoot, out var navigationRootSource))
-			return string.Empty;
+		if (Phantoms.Contains(navigationSource)
+			|| !TryGetNavigationRoot(navigationSource, out var navigationRoot, out var navigationRootSource)
+			|| Phantoms.Contains(navigationRootSource)
+		)
+			return new EmptyNavigationRenderResult();
 
-		if (Phantoms.Contains(navigationRootSource))
-			return string.Empty;
+		var navigationId = ShortId.Create($"{(navigationRootSource, maxLevel).GetHashCode()}");
 
 		if (_renderedNavigationCache.TryGetValue((navigationRootSource, maxLevel), out var value))
-			return value;
+			return new OkNavigationRenderResult
+			{
+				Html = value,
+				Id = navigationId
+			};
 
 		if (navigationRootSource == new Uri("docs-content:///"))
 		{
 			_renderedNavigationCache[(navigationRootSource, maxLevel)] = string.Empty;
-			return string.Empty;
+			return new EmptyNavigationRenderResult();
 		}
 
 		Console.WriteLine($"Rendering navigation for {navigationRootSource}");
@@ -70,7 +76,11 @@ public async Task<string> RenderNavigation(IRootNavigationItem<INavigationModel,
 		value = await ((INavigationHtmlWriter)this).Render(model, ctx);
 		_renderedNavigationCache[(navigationRootSource, maxLevel)] = value;
 
-		return value;
+		return new OkNavigationRenderResult
+		{
+			Html = value,
+			Id = navigationId
+		};
 	}
 
 	private NavigationViewModel CreateNavigationModel(DocumentationGroup group, int maxLevel)