Microsoft.Build.Locator excluded from MSBuild.BuildHost.deps.json file when building with .NET 10 SDK

[mthalman]

The source built SDK for .NET 10 currently doesn't have a functional dotnet-format tool. Attempting to run it on a project results in the following error:

Unhandled exception: Microsoft.CodeAnalysis.MSBuild.RemoteInvocationException: An exception of type System.IO.FileNotFoundException was thrown: Could not load file or assembly 'Microsoft.Build.Locator, Version=1.6.10.0, Culture=neutral, PublicKeyToken=9dff12846e04bfbd'. The system cannot find the file specified.


at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeCoreAsync(Int32 targetObject, String methodName, List1 parameters, Type expectedReturnType, CancellationToken cancellationToken)    at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeAsync[T](Int32 targetObject, String methodName, List1 parameters, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.MSBuild.RemoteBuildHost.LoadProjectFileAsync(String projectFilePath, String languageName, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.DoOperationAndReportProgressAsync[TResult](ProjectLoadOperation operation, String projectPath, String targetFramework, Func1 doFunc)    at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadProjectFileInfosAsync(String projectPath, DiagnosticReportingOptions reportingOptions, CancellationToken cancellationToken)    at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadProjectInfosFromPathAsync(String projectPath, DiagnosticReportingOptions reportingOptions, CancellationToken cancellationToken)    at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadAsync(CancellationToken cancellationToken)    at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.LoadProjectInfoAsync(String projectFilePath, ProjectMap projectMap, IProgress1 progress, ILogger msbuildLogger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.LoadProjectInfoAsync(String projectFilePath, ProjectMap projectMap, IProgress1 progress, ILogger msbuildLogger, CancellationToken cancellationToken)    at Microsoft.CodeAnalysis.MSBuild.MSBuildWorkspace.OpenProjectAsync(String projectFilePath, ILogger msbuildLogger, IProgress1 progress, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.Workspaces.MSBuildWorkspaceLoader.LoadAsync(String solutionOrProjectPath, WorkspaceType workspaceType, String binaryLogPath, Boolean logWorkspaceWarnings, ILogger logger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.CodeFormatter.OpenMSBuildWorkspaceAsync(String solutionOrProjectPath, WorkspaceType workspaceType, Boolean noRestore, Boolean requiresSemantics, String binaryLogPath, Boolean logWorkspaceWarnings, ILogger logger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.CodeFormatter.FormatWorkspaceAsync(FormatOptions formatOptions, ILogger logger, CancellationToken cancellationToken, String binaryLogPath)
at Microsoft.CodeAnalysis.Tools.FormatCommandCommon.FormatAsync(FormatOptions formatOptions, ILogger`1 logger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.Commands.RootFormatCommand.FormatCommandDefaultHandler.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)
at System.CommandLine.Invocation.InvocationPipeline.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)

This was identified in dotnet/sdk#46055 (comment).

This occurs because Microsoft.Build.Locator is not referenced by the sdk/<version>/DotnetTools/dotnet-format/BuildHost-netcore/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.deps.json file. If you manually update the file to reference Microsoft.Build.Locator, dotnet-format will run successfully.

The reason Microsoft.Build.Locator is not in the deps.json file is because a recent SDK change (dotnet/sdk#45259) combined with the Microsoft.Build.Locator package reference being defined with PrivateAssets="All":

roslyn/src/Workspaces/Core/MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj

Line 45 in c2b719c

<PackageReference Include="Microsoft.Build.Locator" PrivateAssets="All" />

This doesn't currently affect the Microsoft-built SDK because that is using assets produced by Roslyn's build which is currently using the .NET 9 SDK. So it will eventually be an issue for the Microsoft-built SDK whenever roslyn updates its global.json to use a .NET 10 SDK. However, this needs to be addressed now because source build builds all repos with the .NET 10 SDK and we want to have a usable dotnet-format tool for the source built SDK in .NET 10 Preview 1.