Use VersioningSystem.None for non-public-reference products

Products without the public-reference feature (e.g. release-notes-only
products like docs-builder) now get VersioningSystem.None instead of
null. This prevents NullReferenceExceptions in version inference when
the product is matched by repository name during doc builds.

VersioningSystem.None is a versionless sentinel (using the existing
99999 convention) with a new VersioningSystemId.None enum value,
making the "no versioning" state explicit rather than relying on null.

Made-with: Cursor

Author: cotti

src/Elastic.Documentation.Configuration/Inference/VersionInference.cs

@@ -30,14 +30,17 @@ public VersioningSystem InferVersion(string repositoryName, IReadOnlyCollection<
 				return versioningFromApplicability;
 		}
 
-		var versioning = ProductsConfiguration.Products.TryGetValue(repositoryName, out var belonging)
-				? belonging.VersioningSystem! //If the page's docset has a name with a direct product match, use the versioning system of the product
-				: ProductsConfiguration.Products.Values.SingleOrDefault(p =>
-					p.Repository is not null && p.Repository.Equals(repositoryName, StringComparison.OrdinalIgnoreCase)) is { } repositoryMatch
-					? repositoryMatch.VersioningSystem! // Verify if the page belongs to a repository linked to a product, and if so, use the versioning system of the product
-					: VersionsConfiguration.VersioningSystems[VersioningSystemId.Stack]; // Fallback to the stack versioning system
-
-		return versioning;
+		var stackFallback = VersionsConfiguration.VersioningSystems[VersioningSystemId.Stack];
+
+		if (ProductsConfiguration.Products.TryGetValue(repositoryName, out var belonging) && belonging.VersioningSystem is not null)
+			return belonging.VersioningSystem;
+
+		var repositoryMatch = ProductsConfiguration.Products.Values
+			.SingleOrDefault(p => p.Repository is not null && p.Repository.Equals(repositoryName, StringComparison.OrdinalIgnoreCase));
+		if (repositoryMatch?.VersioningSystem is not null)
+			return repositoryMatch.VersioningSystem;
+
+		return stackFallback;
 	}
 
 	private VersioningSystem? VersioningFromApplicability(ApplicableTo applicableTo)

src/Elastic.Documentation.Configuration/Products/ProductExtensions.cs

@@ -18,13 +18,22 @@ public static ProductsConfiguration CreateProducts(this ConfigurationFileProvide
 
 		var products = productsDto.Products.ToDictionary(
 			kvp => kvp.Key,
-			kvp => new Product
+			kvp =>
 			{
-				Id = kvp.Key,
-				DisplayName = kvp.Value.Display,
-				VersioningSystem = ResolveVersioningSystem(versionsConfiguration, kvp.Value.Versioning ?? kvp.Key),
-				Repository = kvp.Value.Repository ?? kvp.Key,
-				Features = ResolveFeatures(kvp.Key, kvp.Value.Features)
+				var features = ResolveFeatures(kvp.Key, kvp.Value.Features);
+				var versioningSystem = ResolveVersioningSystem(versionsConfiguration, kvp.Value.Versioning ?? kvp.Key);
+
+				if (versioningSystem is null && !features.PublicReference)
+					versioningSystem = VersioningSystem.None;
+
+				return new Product
+				{
+					Id = kvp.Key,
+					DisplayName = kvp.Value.Display,
+					VersioningSystem = versioningSystem,
+					Repository = kvp.Value.Repository ?? kvp.Key,
+					Features = features
+				};
 			});
 
 		var publicReferenceProducts = products

src/Elastic.Documentation.Configuration/Versions/VersionConfiguration.cs

@@ -23,6 +23,8 @@ public VersioningSystem GetVersioningSystem(VersioningSystemId versioningSystem)
 [EnumExtensions]
 public enum VersioningSystemId
 {
+	[Display(Name = "none")]
+	None,
 	[Display(Name = "stack")]
 	Stack,
 	[Display(Name = "all")]
@@ -152,6 +154,17 @@ public record VersioningSystem
 	/// </summary>
 	public const int VersionlessSentinel = 99999;
 
+	/// <summary>
+	/// A versionless sentinel for products that have no versioning system at all
+	/// (e.g. release-notes-only products without public documentation).
+	/// </summary>
+	public static VersioningSystem None { get; } = new()
+	{
+		Id = VersioningSystemId.None,
+		Base = new SemVersion(VersionlessSentinel, 0, 0),
+		Current = new SemVersion(VersionlessSentinel, 0, 0)
+	};
+
 	public required VersioningSystemId Id { get; init; }
 
 	[YamlMember(Alias = "base")]

tests/Elastic.Documentation.Configuration.Tests/ProductFeaturesTests.cs

@@ -32,6 +32,17 @@ public void ProductWithReleaseNotesOnly_ExcludedFromPublicReference()
 		docsBuilder.Features.ReleaseNotes.Should().BeTrue();
 	}
 
+	[Fact]
+	public void ProductWithoutPublicReference_GetsNoneVersioningSystem()
+	{
+		var config = LoadActualProductsConfiguration();
+		var docsBuilder = config.Products["docs-builder"];
+
+		docsBuilder.VersioningSystem.Should().Be(VersioningSystem.None);
+		docsBuilder.VersioningSystem.IsVersionless.Should().BeTrue();
+		docsBuilder.VersioningSystem.Id.Should().Be(VersioningSystemId.None);
+	}
+
 	[Fact]
 	public void PublicReferenceProducts_ExcludesReleaseNotesOnlyProducts()
 	{