Cannot use MSBuildLocator with multiple versions of Visual Studio for different projects

[vladimirKa002]

Version Used: 4.8.0

Steps to Reproduce:

Tested C# projects (.csproj): project1 and project2.

Projects loading method:

private Project GetProject(string projectPath, MSBuildWorkspace workspace)
{
    return workspace.OpenProjectAsync(projectPath).Result;
}

Installed Visual Studio versions:

16.11.34301.259
17.8.34322.80

Dependecies:

<PackageReference Include="Microsoft.Build" Version="17.8.3" />
<PackageReference Include="Microsoft.Build.Locator" Version="1.6.10" />
<PackageReference Include="Microsoft.Build.Tasks.Core" Version="17.8.3" />
<PackageReference Include="Microsoft.Build.Utilities.Core" Version="17.8.3" />
<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
<PackageReference Include="Microsoft.CodeAnalysis.Common" Version="4.8.0" />
<PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.8.0" />
<PackageReference Include="Microsoft.CodeAnalysis.VisualBasic.Workspaces" Version="4.8.0" />
<PackageReference Include="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.8.0" />

Expected Behavior: Projects should be loaded normally with all documents from the path.

Actual Behavior:

When I run the following code snippet at the start of the analysis, the first project has zero documents. However, the second one gets loaded normally:

if (!MSBuildLocator.IsRegistered)
{
    var vsi = MSBuildLocator.QueryVisualStudioInstances();
    MSBuildLocator.RegisterInstance(vsi.First()); // First installed version
}

But when I select the second VS version MSBuildLocator, the first project works fine, but the second one gets stuck forever.

Instead of this code, I also tried MSBuildLocator.RegisterDefaults();, but it behaved similarly to when the first version is selected.

[jasonmalinowski]

So the fact you can't use different versions of MSBuild for different projects (at least with MSBuildLocator) would be expected, since once MSBuildLocator has loaded a VS version of MSBuild we can't unload it -- there's not AppDomain isolation or anything in the way we'd need to make that work. That said, this feels like a bit of a red herring -- I wouldn't expect a high version to not work with something that a lower version does.

@vladimirKa00217 I'd suggest trying one of two things:

1. Once we get the 4.9.0-2.final packages of Workspaces.MSBuild uploaded, try those. Those move the actual invoking of MSBuild to a separate process where we ensure we get binding redirects and such set up. It also means you registering MSBuildLocator in process doesn't do anything anymore -- we're calling it in the other processes. Your SDK-style project would also get loaded in a .NET Core process which might help compatibility there since we'll use separate processes for each.
2. If that doesn't work (or you want to try to analyze this a bit sooner), subscribe to MSBuildWorkspace.WorkspaceFailed as an event, and report back here what log messages get fired to that. That might give us a bit of a hint as to what's breaking here.

But there's a good chance the work we did for those newer packages might fix this.

[jasonmalinowski]

Those packages are now up, so @vladimirKa002 want to give those a shot and report back?

[jasonmalinowski]

@vladimirKa002 Any chance you can try the new packages and report back?

[vladimirKa002]

@jasonmalinowski, thank you for your response. I tried a new package, and it solved the problem. Now I can perform the analysis of both projects normally.

[jasonmalinowski]

Awesome, thanks for confirming! And to be clear: with the new packages you don't need MSBuildLocator at all anymore, so feel free to remove the package references and any use of the API.

[vladimirKa002]

@jasonmalinowski, could you please check this issue. Seems like after upgrading the packages to a newer version, analyses stopped working in Docker environment.

[jasonmalinowski]

@vladimirKa002 Thanks for the ping, since that issue had gotten closed we otherwise wouldn't have seen it.