MSBuildSdkResolver throws ArgumentException when solution path is an empty string

[jeffkl]

Describe the bug

Reported as part of dotnet/msbuild#7453

When an MSBuild project SDK is being resolved in some cases (ie Visual Studio), the SdkResolverContext has an empty string for the solution path. The MSBuildSdkResolver tries to call Path.GetDirectoryName() on an empty string and an ArgumentException is thrown. The code is trying to fall back to using the project path but is only checking for null, not an empty string.

sdk/src/Resolvers/Microsoft.DotNet.MSBuildSdkResolver/MSBuildSdkResolver.cs

Line 91 in b69e8f5

string globalJsonStartDir = Path.GetDirectoryName(context.SolutionFilePath ?? context.ProjectFilePath);

To Reproduce

Evalute an MSBuild project file with a solution path as an empty string.

Exceptions (if any)

Further technical details

• Include the output of dotnet --info
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

[jeffkl]

Fixed by #24333