[Bug] Error loading project for misc file in VSCode

[dibarbet]

Opened a project, then opened a random .cs (not part the project). Got a warning saying the project failed to load for the file on disk with the following stack:

2025-05-14 18:33:25.254 [info] [Error - 6:33:25 PM] [textDocument/_vs_getProjectContexts] [LanguageServerProjectLoader] Error while loading c:\Users\dabarbet\Downloads\file_on_disk.cs: Exception thrown: Microsoft.CodeAnalysis.MSBuild.RemoteInvocationException: An exception of type System.ArgumentException was thrown: All build submissions in a build must use project instances originating from the same project collection.
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeCoreAsync(Int32 targetObject, String methodName, List`1 parameters, Type expectedReturnType, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 186
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeAsync[T](Int32 targetObject, String methodName, List`1 parameters, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 135
   at Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.LanguageServerProjectLoader.ReloadProjectAsync(ProjectToLoad projectToLoad, ToastErrorReporter toastErrorReporter, BuildHostProcessManager buildHostProcessManager, CancellationToken cancellationToken) in /_/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectLoader.cs:line 226

I haven't managed to reproduce it extremely often, but I opened it while the original project was loading (so potentially multiple misc file loads happening at once)?

[RikkiGibson]

I also saw this bug. Had difficulty repro'ing, but, it sounds like we are batching build submissions that should not be batched.

[RikkiGibson]

I think the problem is around here:

roslyn/src/Workspaces/MSBuild/BuildHost/Build/ProjectBuildManager.cs

Line 169 in 3f63dd1

public (MSB.Evaluation.Project? project, DiagnosticLog log) LoadProject(string path, Stream readStream)

The calling context appears to enter batch build mode. But this method doesn't handle that situation properly.

[jasonswearingen]

@RikkiGibson I see this error often, as it leaves temp build files scattered through my projects. How can I track when this is available? I am using the latest VSCode insiders build and see it today.

[jasonswearingen]

example:

2025-05-23 14:58:34.816 [info] [Info  - 2:58:34 PM] [solution/open] [LanguageServerProjectSystem] Loading v:\r-Cleartrix\Cleartrix\apps\cleartrix-dotnet\CleartrixDotNet.sln...
2025-05-23 14:58:35.778 [info] [Error - 2:58:35 PM] [textDocument/diagnostic] [LanguageServerProjectLoader] Error while loading v:\r-Cleartrix\Cleartrix\apps\cleartrix-dotnet\private-proj\Cleartrix.Cloud.Tests\EndpointTests.cs: Exception thrown: Microsoft.CodeAnalysis.MSBuild.RemoteInvocationException: An exception of type System.ArgumentException was thrown: All build submissions in a build must use project instances originating from the same project collection.
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeCoreAsync(Int32 targetObject, String methodName, List`1 parameters, Type expectedReturnType, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 186
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeAsync[T](Int32 targetObject, String methodName, List`1 parameters, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 135
   at Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.LanguageServerProjectLoader.ReloadProjectAsync(ProjectToLoad projectToLoad, ToastErrorReporter toastErrorReporter, BuildHostProcessManager buildHostProcessManager, CancellationToken cancellationToken) in /_/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectLoader.cs:line 224
2025-05-23 14:58:35.779 [info] [Error - 2:58:35 PM] [textDocument/diagnostic] [LanguageServerProjectLoader] Error while loading v:\r-Cleartrix\Cleartrix\apps\cleartrix-dotnet\private-proj\Cleartrix.Cloud.Tests\SampleTests.cs: Exception thrown: Microsoft.CodeAnalysis.MSBuild.RemoteInvocationException: An exception of type System.ArgumentException was thrown: All build submissions in a build must use project instances originating from the same project collection.
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeCoreAsync(Int32 targetObject, String methodName, List`1 parameters, Type expectedReturnType, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 186
   at Microsoft.CodeAnalysis.MSBuild.RpcClient.InvokeAsync[T](Int32 targetObject, String methodName, List`1 parameters, CancellationToken cancellationToken) in /_/src/Workspaces/MSBuild/Core/Rpc/RpcClient.cs:line 135
   at Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.LanguageServerProjectLoader.ReloadProjectAsync(ProjectToLoad projectToLoad, ToastErrorReporter toastErrorReporter, BuildHostProcessManager buildHostProcessManager, CancellationToken cancellationToken) in /_/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectLoader.cs:line 224

[RikkiGibson]

A new prerelease should go out next week, but, you can probably stop the unwanted behavior by setting "dotnet.projects.enableFileBasedPrograms": false in your workspace settings.