[Bug] Installation of .NET 8 breaks docfx metadata

[groogiam]

Describe the bug
I recently updated my Visual Studio 2022 instance which updated my .NET SDK to version 8 and removed some of the old SDK's. Only having .NET SDK 8 breaks docfx metadata processing with the following error

docfx metadata docs\docfx.json
ExtractMetadataException: No instances of MSBuild could be detected.
Try calling RegisterInstance or RegisterMSBuildPath to manually register one.
     InvalidOperationException: No instances of MSBuild could be detected.
     Try calling RegisterInstance or RegisterMSBuildPath to manually register one.
       at VisualStudioInstance RegisterDefaults()
       at void EnsureMSBuildLocator() in DotnetApiCatalog.cs:131
  at void EnsureMSBuildLocator() in DotnetApiCatalog.cs:139
  at async Task Exec(MetadataJsonConfig config, DotnetApiOptions options, string configDirectory, string outputDirectory
     ) in DotnetApiCatalog.cs:57
  at void <Execute>b__0() in MetadataCommand.cs:18
  at int Run(LogOptions options, Action run) in CommandHelper.cs:43
  at int Execute(CommandContext context, MetadataCommandOptions options) in MetadataCommand.cs:14
  at Task<int> Execute(CommandContext context, CommandSettings settings) in CommandOfT.cs:40
  at Task<int> Execute(CommandTree leaf, CommandTree tree, CommandContext context, ITypeResolver resolver,
     IConfiguration configuration) in CommandExecutor.cs:144
  at async Task<int> Execute(IConfiguration configuration, IEnumerable<string> args) in CommandExecutor.cs:85
  at async Task<int> RunAsync(IEnumerable<string> args) in CommandApp.cs:84

To Reproduce
Steps to reproduce the behavior:

1. run docfx metadata docs\docfx.json

Expected behavior
Metadata should process.

Context (please complete the following information):

• OS: Windows 10 Pro
• Docfx version: [e.g. 2.59.0] 2.73.2+8a60af927dcb1a034de840021cc7268c309f9d17

Additional context
dotnet --list-sdks output

8.0.100 [C:\Program Files\dotnet\sdk]

[yufeih]

Support of .NET 8.0.100 hasn't landed yet, pending on the official release of roslyn compiler for .NET 8. #9424

[paulushub]

@groogiam Just for information, are you using some .NET 8 specific features?
For a simple project I updated docfx dotnet tool update -g docfx, it builds both locally and github workflow.

[groogiam]

@paulushub I am not using any specific .NET 8 features, in fact all my projects are still targeting .NET 7.
Your example above is using the default target for docfx which I believe is docfx build. What is broken is docfx metadata which is used to generate api docs from csproj. As per #7662 this relies on Visual Studio to or the Visual Studio build tools. Thanks.

[groogiam]

@yufeih It looks like #9424 is merged so would I be correct in assuming that this will be released sometime in the next few days?

Thanks for your help.

[yufeih]

Yes