Unable to find fallback package folder '/usr/share/dotnet/sdk/NuGetFallbackFolder'

Issue Description

VS Code constatly notifies me, that it cannot load a project or it has difficulties loading it. The project may build fine and work, still Omnisharp seems to either not see dependencies, all completely fail even on .NET assemblies.

When I delete bin/obj folders, the things become even funnier:

Steps to Reproduce

Create a new project .NET project(classlib) using dotnet new from WSL terminal in VS Code.

Expected Behavior

C# projects should be loaded fine, I should be able to browse classes and access symbols.

Actual Behavior

C# projects go crazy and even framework classes are marked as missing.

Logs

OmniSharp log

Starting OmniSharp server at 8.08.2019, 10:11:01 Target: d:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend

OmniSharp server started. Path: C:\Users\kamz.vscode\extensions\ms-vscode.csharp-1.21.0.omnisharp\1.34.0\OmniSharp.exe PID: 20692

    Starting OmniSharp on Windows 6.2.9200.0 (x64)

    DotNetPath set to dotnet

    Located 1 MSBuild instance(s)
        1: StandAlone 16.0 - "C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild\Current\Bin"

    MSBUILD_EXE_PATH environment variable set to 'C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild\Current\Bin\MSBuild.exe'

    Registered MSBuild instance: StandAlone 16.0 - "C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild\Current\Bin"
        CscToolExe = csc.exe
        CscToolPath = C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild\Current\Bin\Roslyn
        MSBuildExtensionsPath = C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild
        MSBuildToolsPath = C:\Users\kamz\.vscode\extensions\ms-vscode.csharp-1.21.0\.omnisharp\1.34.0\.msbuild\Current\Bin

    Detecting Cake files in 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend'.

    Could not find any Cake files

    No solution files found in 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend'

    Queue project update for 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Detecting CSX files in 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend'.

    Could not find any CSX files

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpFormattingWorkspaceOptionsProvider, Order: 0

    Loading project: d:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.RenameWorkspaceOptionsProvider, Order: 100

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.EditorConfigWorkspaceOptionsProvider, Order: 200

    Configuration finished.

    Omnisharp server running using Stdio at location 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend' on host 21628.

    Successfully loaded project file 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'.

    Adding project 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Update project: LicznikNET.Modules

    Queue project update for 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Queue project update for 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Queue project update for 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Queue project update for 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'

    Loading project: d:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj

    The "ResolvePackageAssets" task failed unexpectedly.

NuGet.Packaging.Core.PackagingException: Unable to find fallback package folder ‘/usr/share/dotnet/sdk/NuGetFallbackFolder’. at NuGet.Packaging.FallbackPackagePathResolver…ctor(String userPackageFolder, IEnumerable1 fallbackPackageFolders) at Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(LockFile lockFile, String projectPath) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheWriter..ctor(ResolvePackageAssets task, Stream stream) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader.CreateReaderFromDisk(ResolvePackageAssets task, Byte[] settingsHash) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader..ctor(ResolvePackageAssets task) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ReadItemGroups() at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ExecuteCore() at Microsoft.NET.Build.Tasks.TaskBase.Execute() at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext() [warn]: OmniSharp.MSBuild.ProjectManager Failed to load project file 'd:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj'. d:\TheCloudTheory\Apps\LicznikNET\LicznikNET.Backend\LicznikNET.Modules\LicznikNET.Modules.csproj C:\Program Files\dotnet\sdk\2.2.401\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(208,5): Error: The "ResolvePackageAssets" task failed unexpectedly. NuGet.Packaging.Core.PackagingException: Unable to find fallback package folder '/usr/share/dotnet/sdk/NuGetFallbackFolder'. at NuGet.Packaging.FallbackPackagePathResolver..ctor(String userPackageFolder, IEnumerable1 fallbackPackageFolders) at Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(LockFile lockFile, String projectPath) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheWriter…ctor(ResolvePackageAssets task, Stream stream) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader.CreateReaderFromDisk(ResolvePackageAssets task, Byte[] settingsHash) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader…ctor(ResolvePackageAssets task) at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ReadItemGroups() at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ExecuteCore() at Microsoft.NET.Build.Tasks.TaskBase.Execute() at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()

    Update project: LicznikNET.Modules</details>

C# log

Post the output from Output-->C# here

Environment information

VSCode version: 1.36.1 C# Extension: 1.21.0

Dotnet Information

.NET Core SDK (reflecting any global.json): Version: 2.2.401 Commit: 729b316c13

Runtime Environment: OS Name: Windows OS Version: 10.0.17763 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\2.2.401\

Host (useful for support): Version: 2.2.6 Commit: 7dac9b1b51

.NET Core SDKs installed: 2.2.401 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed: Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs: https://aka.ms/dotnet-download

Visual Studio Code Extensions

Extension	Author	Version
azure-account	ms-vscode	0.8.4
azurerm-vscode-tools	msazurermtools	0.6.0
csharp	ms-vscode	1.21.0
gitlens	eamodio	9.9.3
Go	ms-vscode	0.11.4
markdown-all-in-one	yzhang	2.4.2
powershell	ms-vscode	2019.5.0
shell-format	foxundermoon	6.1.1
terraform	mauve	1.3.12
vscode-azurefunctions	ms-azuretools	0.17.2-alpha
vscode-azureterraform	ms-azuretools	0.2.4
vscode-docker	ms-azuretools	0.7.0
xml	DotJoshJohnson	2.5.0

[filipw]

OmniSharp runs on the Windows file system and the WSL file system is not available to it, this is a known problem. Same thing happens i.e. if you create a dotnet project on a Mac and then try to use it with OmniSharp on Windows in a VM.

You should restore your project from the Windows command line as a workaround.

[emhacker]

Encountered the same issue, and I confirm that the workaround worked for me. I just wonder - is there a way to manually configure which OmniServer executable to connect to? (e.g., Linux, Windows)?