After upgrading Microsoft.CodeAnalysis.CSharp.Workspace from 4.2.0 to 4.3.0 it started throwing at runtime

[Swiftly1]

Version Used:

4.3.0

Error Thrown:

Unhandled exception. System.InvalidOperationException: Service of type 'Microsoft.CodeAnalysis.Classification.IEmbeddedLanguageClassificationService' is required to accomplish the task but is not available from the workspace. at Microsoft.CodeAnalysis.Host.HostLanguageServices.GetRequiredService[TLanguageService]() in /_/src/Workspaces/Core/Portable/Workspace/Host/HostLanguageServices.cs:line 39 at Microsoft.CodeAnalysis.Classification.Classifier.GetClassifiedSpans(HostWorkspaceServices workspaceServices, Project project, SemanticModel semanticModel, TextSpan textSpan, ClassificationOptions options, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Classification/Classifier.cs:line 61 at Microsoft.CodeAnalysis.Classification.Classifier.GetClassifiedSpansAsync(Document document, TextSpan textSpan, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Classification/Classifier.cs:line 31 at Program.Main()

Workaround:

Adding:

<PackageReference Include="Microsoft.CodeAnalysis.CSharp.Features" Version="4.3.0" />

Repro:

using System;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Text;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Classification;
	
public class Program
{
	private static readonly ImmutableArray<MetadataReference> _coreReferences =
	ImmutableArray.Create<MetadataReference>
	(
		MetadataReference.CreateFromFile(typeof(object).Assembly.Location
	));
	
	public static void Main()
	{
		var code = "public void Test() {}";
		var host = MefHostServices.Create(MefHostServices.DefaultAssemblies);
		var sourceText = SourceText.From(code);
		var workspace = new AdhocWorkspace(host);

		var doc = workspace
				  .AddProject("Test", LanguageNames.CSharp)
				  .AddMetadataReferences(_coreReferences)
				  .AddDocument("TestFile", sourceText);

		var spans = Classifier.GetClassifiedSpansAsync(doc, new TextSpan(0, code.Length)).GetAwaiter().GetResult();
	}
}

/cc @sharwell

Suspected patch
#61994