`dotnet nuget why` should skip projects it cannot load

[IanKemp]

NuGet Product Used

dotnet.exe

Product Version

All

Worked before?

No response

Impact

It's more difficult to complete my work

Repro Steps & Context

Run dotnet nuget why <sln-file-name> <pkg-or-proj-name> against a solution that contains a project that uses MSBuild variables to import other files, e.g. the below from a legacy EF6 project:

<PropertyGroup>
  <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">17.0</VisualStudioVersion>
  <SSDTExists Condition="Exists('$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\SSDT\Microsoft.Data.Tools.Schema.SqlTasks.targets')">True</SSDTExists>
  <VisualStudioVersion Condition="'$(SSDTExists)' == ''">17.0</VisualStudioVersion>
</PropertyGroup>
<Import Condition="'$(SQLDBExtensionsRefPath)' != ''" Project="$(SQLDBExtensionsRefPath)\Microsoft.Data.Tools.Schema.SqlTasks.targets" />
<Import Condition="'$(SQLDBExtensionsRefPath)' == ''" Project="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\SSDT\Microsoft.Data.Tools.Schema.SqlTasks.targets" />

It fails with the following error:

Unhandled exception: Microsoft.Build.Exceptions.InvalidProjectFileException: The imported file "$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\SSDT\Microsoft.Data.Tools.Schema.SqlTasks.targets" does not exist and appears to be part of a Visual Studio component. This file may require MSBuild.exe in order to be imported successfully, and so may fail to build in the dotnet CLI.   path\to\offending.sqlproj
   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject(String errorSubCategoryResourceName, IElementLocation elementLocation, String resourceName, Object[] args)
   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1](IElementLocation elementLocation, String resourceName, T1 arg0)
   at Microsoft.Build.Evaluation.Evaluator`4.ExpandAndLoadImportsFromUnescapedImportExpression(String directoryOfImportingFile, ProjectImportElement importElement, String unescapedExpression, Boolean throwOnFileNotExistsError, List`1& imports)
   at Microsoft.Build.Evaluation.Evaluator`4.ExpandAndLoadImportsFromUnescapedImportExpressionConditioned(String directoryOfImportingFile, ProjectImportElement importElement, List`1& projects, SdkResult& sdkResult)
   at Microsoft.Build.Evaluation.Evaluator`4.ExpandAndLoadImports(String directoryOfImportingFile, ProjectImportElement importElement, SdkResult& sdkResult)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)
   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)
   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate()
   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate(IEvaluatorData`4 data, Project project, ProjectRootElement root, ProjectLoadSettings loadSettings, Int32 maxNodeCount, PropertyDictionary`1 environmentProperties, ICollection`1 propertiesFromCommandLine, ILoggingService loggingService, IItemFactory`2 itemFactory, IToolsetProvider toolsetProvider, IDirectoryCacheFactory directoryCacheFactory, ProjectRootElementCacheBase projectRootElementCache, BuildEventContext buildEventContext, ISdkResolverService sdkResolverService, Int32 submissionId, EvaluationContext evaluationContext, Boolean interactive)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.Reevaluate(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.ReevaluateIfNecessary(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at NuGet.CommandLine.XPlat.Commands.Why.WhyCommandRunner.FindAssetsFiles(String path, IAnsiConsole logger)+MoveNext()
   at NuGet.CommandLine.XPlat.Commands.Why.WhyCommandRunner.ExecuteCommand(WhyCommandArgs whyCommandArgs)
   at NuGet.CommandLine.XPlat.Commands.Why.WhyCommand.<>c__DisplayClass3_0.<<Register>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Invocation.InvocationPipeline.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)

and no other projects in that solution are listed. Projects that cannot be loaded should instead be skipped with an appropriate warning output.

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