Add crosslinks to toc: in docset.yml

docs/_docset.yml

@@ -149,3 +149,7 @@ toc:
           - folder: baz
             children:
               - file: qux.md
+      - title: "Getting Started Guide"
+        crosslink: docs-content://get-started/introduction.md
+      - title: "Test title"
+        crosslink: docs-content://solutions/search/elasticsearch-basics-quickstart.md

docs/configure/content-set/navigation.md

@@ -72,12 +72,38 @@ cross_links:
   - docs-content
 ```
 
+#### Adding cross-links in Markdown content
+
 To link to a document in the `docs-content` repository, you would write the link as follows:
 
-```
+```markdown
 [Link to docs-content doc](docs-content://directory/another-directory/file.md)
 ```
 
+You can also link to specific anchors within the document:
+
+```markdown
+[Link to specific section](docs-content://directory/file.md#section-id)
+```
+
+#### Adding cross-links in navigation
+
+Cross-links can also be included in navigation structures. When creating a `toc.yml` file or defining navigation in `docset.yml`, you can add cross-links as follows:
+
+```yaml
+toc:
+  - file: index.md
+  - title: External Documentation
+    crosslink: docs-content://directory/file.md
+  - folder: local-section
+    children:
+      - file: index.md
+      - title: API Reference
+        crosslink: elasticsearch://api/index.html
+```
+
+Cross-links in navigation will be automatically resolved during the build process, maintaining consistent linking between related documentation across repositories.
+
 ### `exclude`
 
 Files to exclude from the TOC. Supports glob patterns.

src/Elastic.Documentation.Configuration/Builder/TableOfContentsConfiguration.cs

@@ -129,6 +129,8 @@ private IReadOnlyCollection<ITocItem> ReadChildren(YamlStreamReader reader, KeyV
 	private IEnumerable<ITocItem>? ReadChild(YamlStreamReader reader, YamlMappingNode tocEntry, string parentPath)
 	{
 		string? file = null;
+		string? crossLink = null;
+		string? title = null;
 		string? folder = null;
 		string[]? detectionRules = null;
 		TableOfContentsConfiguration? toc = null;
@@ -148,6 +150,13 @@ private IReadOnlyCollection<ITocItem> ReadChildren(YamlStreamReader reader, KeyV
 					hiddenFile = key == "hidden";
 					file = ReadFile(reader, entry, parentPath);
 					break;
+				case "title":
+					title = reader.ReadString(entry);
+					break;
+				case "crosslink":
+					hiddenFile = false;
+					crossLink = reader.ReadString(entry);
+					break;
 				case "folder":
 					folder = ReadFolder(reader, entry, parentPath);
 					parentPath += $"{Path.DirectorySeparatorChar}{folder}";
@@ -199,6 +208,12 @@ private IReadOnlyCollection<ITocItem> ReadChildren(YamlStreamReader reader, KeyV
 			return [new FileReference(this, path, hiddenFile, children ?? [])];
 		}
 
+		if (crossLink is not null)
+		{
+			// No validation here - we'll validate cross-links separately
+			return [new CrossLinkReference(this, crossLink, title, hiddenFile, children ?? [])];
+		}
+
 		if (folder is not null)
 		{
 			if (children is null)

src/Elastic.Documentation.Configuration/TableOfContents/ITocItem.cs

@@ -14,6 +14,9 @@ public interface ITocItem
 public record FileReference(ITableOfContentsScope TableOfContentsScope, string RelativePath, bool Hidden, IReadOnlyCollection<ITocItem> Children)
 	: ITocItem;
 
+public record CrossLinkReference(ITableOfContentsScope TableOfContentsScope, string CrossLinkUri, string? Title, bool Hidden, IReadOnlyCollection<ITocItem> Children)
+	: ITocItem;
+
 public record FolderReference(ITableOfContentsScope TableOfContentsScope, string RelativePath, IReadOnlyCollection<ITocItem> Children)
 	: ITocItem;
 

src/Elastic.Markdown/IO/DocumentationSet.cs

@@ -209,6 +209,25 @@ public DocumentationSet(
 			.ToDictionary(kv => kv.Item1, kv => kv.Item2)
 			.ToFrozenDictionary();
 
+		// Validate cross-repo links in navigation
+
+		try
+		{
+			// First ensure links are fetched - this is essential for resolving links properly
+			_ = LinkResolver.FetchLinks(new Cancel()).GetAwaiter().GetResult();
+
+			NavigationCrossLinkValidator.ValidateNavigationCrossLinksAsync(
+				Tree,
+				LinkResolver,
+				(msg) => Context.EmitError(Context.ConfigurationPath, msg)
+			).GetAwaiter().GetResult();
+		}
+		catch (Exception e)
+		{
+			// Log the error but don't fail the build
+			Context.EmitError(Context.ConfigurationPath, $"Error validating cross-links in navigation: {e.Message}");
+		}
+
 		ValidateRedirectsExists();
 	}
 
@@ -222,6 +241,10 @@ private void UpdateNavigationIndex(IReadOnlyCollection<INavigationItem> navigati
 					var fileIndex = Interlocked.Increment(ref navigationIndex);
 					fileNavigationItem.NavigationIndex = fileIndex;
 					break;
+				case CrossLinkNavigationItem crossLinkNavigationItem:
+					var crossLinkIndex = Interlocked.Increment(ref navigationIndex);
+					crossLinkNavigationItem.NavigationIndex = crossLinkIndex;
+					break;
 				case DocumentationGroup documentationGroup:
 					var groupIndex = Interlocked.Increment(ref navigationIndex);
 					documentationGroup.NavigationIndex = groupIndex;
@@ -241,6 +264,9 @@ private static IReadOnlyCollection<INavigationItem> CreateNavigationLookup(INavi
 		if (item is ILeafNavigationItem<INavigationModel> leaf)
 			return [leaf];
 
+		if (item is CrossLinkNavigationItem crossLink)
+			return [crossLink];
+
 		if (item is INodeNavigationItem<INavigationModel, INavigationItem> node)
 		{
 			var items = node.NavigationItems.SelectMany(CreateNavigationLookup);
@@ -254,6 +280,8 @@ public static (string, INavigationItem)[] Pairs(INavigationItem item)
 	{
 		if (item is FileNavigationItem f)
 			return [(f.Model.CrossLink, item)];
+		if (item is CrossLinkNavigationItem cl)
+			return [(cl.Url, item)]; // Use the URL as the key for cross-links
 		if (item is DocumentationGroup g)
 		{
 			var index = new List<(string, INavigationItem)>

src/Elastic.Markdown/IO/Navigation/CrossLinkNavigationItem.cs

@@ -0,0 +1,67 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// 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.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Elastic.Documentation.Site.Navigation;
+
+namespace Elastic.Markdown.IO.Navigation;
+
+[DebuggerDisplay("CrossLink: {Url}")]
+public record CrossLinkNavigationItem : ILeafNavigationItem<INavigationModel>
+{
+	// Override Url accessor to use ResolvedUrl if available
+	string INavigationItem.Url => ResolvedUrl ?? Url;
+	public CrossLinkNavigationItem(string url, string? title, DocumentationGroup group, bool hidden = false)
+	{
+		_url = url;
+		NavigationTitle = title ?? GetNavigationTitleFromUrl(url);
+		Parent = group;
+		NavigationRoot = group.NavigationRoot;
+		Hidden = hidden;
+	}
+
+	private string GetNavigationTitleFromUrl(string url)
+	{
+		// Extract a decent title from the URL
+		try
+		{
+			if (Uri.TryCreate(url, UriKind.Absolute, out var uri))
+			{
+				// Get the last segment of the path and remove extension
+				var lastSegment = uri.AbsolutePath.Split('/').Last();
+				lastSegment = Path.GetFileNameWithoutExtension(lastSegment);
+
+				// Convert to title case (simple version)
+				if (!string.IsNullOrEmpty(lastSegment))
+				{
+					var words = lastSegment.Replace('-', ' ').Replace('_', ' ').Split(' ');
+					var titleCase = string.Join(" ", words.Select(w =>
+						string.IsNullOrEmpty(w) ? "" : char.ToUpper(w[0]) + w[1..].ToLowerInvariant()));
+					return titleCase;
+				}
+			}
+		}
+		catch
+		{
+			// Fall back to URL if parsing fails
+		}
+
+		return url;
+	}
+
+	public INodeNavigationItem<INavigationModel, INavigationItem>? Parent { get; set; }
+	public IRootNavigationItem<INavigationModel, INavigationItem> NavigationRoot { get; }
+	// Original URL from the cross-link
+	private readonly string _url;
+
+	// Store resolved URL for rendering
+	public string? ResolvedUrl { get; set; }
+
+	// Implement the INavigationItem.Url property to use ResolvedUrl if available
+	public string Url => ResolvedUrl ?? _url; public string NavigationTitle { get; }
+	public int NavigationIndex { get; set; }
+	public bool Hidden { get; }
+	public INavigationModel Model => null!; // Cross-link has no local model
+}

src/Elastic.Markdown/IO/Navigation/DocumentationGroup.cs

@@ -119,7 +119,13 @@ void AddToNavigationItems(INavigationItem item, ref int fileIndex)
 
 		foreach (var tocItem in lookups.TableOfContents)
 		{
-			if (tocItem is FileReference file)
+			if (tocItem is CrossLinkReference crossLink)
+			{
+				// Create a special navigation item for cross-repository links
+				var crossLinkItem = new CrossLinkNavigationItem(crossLink.CrossLinkUri, crossLink.Title, this, crossLink.Hidden);
+				AddToNavigationItems(crossLinkItem, ref fileIndex);
+			}
+			else if (tocItem is FileReference file)
 			{
 				if (!lookups.FlatMappedFiles.TryGetValue(file.RelativePath, out var d))
 				{

src/Elastic.Markdown/IO/Navigation/NavigationCrossLinkValidator.cs

@@ -0,0 +1,94 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// 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;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Elastic.Documentation.Site.Navigation;
+using Elastic.Markdown.Links.CrossLinks;
+
+namespace Elastic.Markdown.IO.Navigation;
+
+public static class NavigationCrossLinkValidator
+{
+	public static async Task ValidateNavigationCrossLinksAsync(
+		INavigationItem root,
+		ICrossLinkResolver crossLinkResolver,
+		Action<string> errorEmitter)
+	{
+		// Ensure cross-links are fetched before validation
+		_ = await crossLinkResolver.FetchLinks(new Cancel());
+
+		// Collect all navigation items that contain cross-repo links
+		var itemsWithCrossLinks = FindNavigationItemsWithCrossLinks(root);
+
+		foreach (var item in itemsWithCrossLinks)
+		{
+			if (item is CrossLinkNavigationItem crossLinkItem)
+			{
+				var url = crossLinkItem.Url;
+				if (url != null && Uri.TryCreate(url, UriKind.Absolute, out var crossUri) &&
+					crossUri.Scheme != "http" && crossUri.Scheme != "https")
+				{
+					// Try to resolve the cross-link URL
+					if (crossLinkResolver.TryResolve(errorEmitter, crossUri, out var resolvedUri))
+					{
+						// If resolved successfully, set the resolved URL
+						crossLinkItem.ResolvedUrl = resolvedUri.ToString();
+					}
+					else
+					{
+						// Error already emitted by CrossLinkResolver
+						// But we won't fail the build - just display the original URL
+					}
+				}
+			}
+			else if (item is FileNavigationItem fileItem &&
+					fileItem.Url != null &&
+					Uri.TryCreate(fileItem.Url, UriKind.Absolute, out var fileUri) &&
+					fileUri.Scheme != "http" &&
+					fileUri.Scheme != "https")
+			{
+				// Cross-link URL detected in a FileNavigationItem, but we're not validating it yet
+			}
+		}
+
+		return;
+	}
+
+	private static List<INavigationItem> FindNavigationItemsWithCrossLinks(INavigationItem item)
+	{
+		var results = new List<INavigationItem>();
+
+		// Check if this item has a cross-link
+		if (item is CrossLinkNavigationItem crossLinkItem)
+		{
+			var url = crossLinkItem.Url;
+			if (url != null &&
+				Uri.TryCreate(url, UriKind.Absolute, out var uri) &&
+				uri.Scheme != "http" &&
+				uri.Scheme != "https")
+			{
+				results.Add(item);
+			}
+		}
+		else if (item is FileNavigationItem fileItem &&
+				fileItem.Url != null &&
+				Uri.TryCreate(fileItem.Url, UriKind.Absolute, out var fileUri) &&
+				fileUri.Scheme != "http" &&
+				fileUri.Scheme != "https")
+		{
+			results.Add(item);
+		}       // Recursively check children if this is a container
+		if (item is INodeNavigationItem<INavigationModel, INavigationItem> containerItem)
+		{
+			foreach (var child in containerItem.NavigationItems)
+			{
+				results.AddRange(FindNavigationItemsWithCrossLinks(child));
+			}
+		}
+
+		return results;
+	}
+}

src/Elastic.Markdown/Links/CrossLinks/ConfigurationCrossLinkFetcher.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System.Collections.Frozen;
+using Elastic.Documentation;
 using Elastic.Documentation.Configuration.Builder;
 using Elastic.Documentation.LinkIndex;
 using Elastic.Documentation.Links;
@@ -12,18 +13,48 @@ namespace Elastic.Markdown.Links.CrossLinks;
 
 public class ConfigurationCrossLinkFetcher(ILoggerFactory logFactory, ConfigurationFile configuration, ILinkIndexReader linkIndexProvider) : CrossLinkFetcher(logFactory, linkIndexProvider)
 {
+	private readonly ILogger _logger = logFactory.CreateLogger(nameof(ConfigurationCrossLinkFetcher));
+
 	public override async Task<FetchedCrossLinks> Fetch(Cancel ctx)
 	{
 		var linkReferences = new Dictionary<string, RepositoryLinks>();
 		var linkIndexEntries = new Dictionary<string, LinkRegistryEntry>();
 		var declaredRepositories = new HashSet<string>();
+
 		foreach (var repository in configuration.CrossLinkRepositories)
 		{
 			_ = declaredRepositories.Add(repository);
-			var linkReference = await Fetch(repository, ["main", "master"], ctx);
-			linkReferences.Add(repository, linkReference);
-			var linkIndexReference = await GetLinkIndexEntry(repository, ctx);
-			linkIndexEntries.Add(repository, linkIndexReference);
+			try
+			{
+				var linkReference = await Fetch(repository, ["main", "master"], ctx);
+				linkReferences.Add(repository, linkReference);
+
+				var linkIndexReference = await GetLinkIndexEntry(repository, ctx);
+				linkIndexEntries.Add(repository, linkIndexReference);
+			}
+			catch (Exception ex)
+			{
+				// Log the error but continue processing other repositories
+				_logger.LogWarning(ex, "Error fetching link data for repository '{Repository}'. Cross-links to this repository may not resolve correctly.", repository);
+
+				// Add an empty entry so we at least recognize the repository exists
+				if (!linkReferences.ContainsKey(repository))
+				{
+					linkReferences.Add(repository, new RepositoryLinks
+					{
+						Links = [],
+						Origin = new GitCheckoutInformation
+						{
+							Branch = "main",
+							RepositoryName = repository,
+							Remote = "origin",
+							Ref = "refs/heads/main"
+						},
+						UrlPathPrefix = "",
+						CrossLinks = []
+					});
+				}
+			}
 		}
 
 		return new FetchedCrossLinks