Errors displayed in editor when referencing F# project on an C# project

Environment data

dotnet --info output:

SDK .NET Core (reflétant tous les global.json) :
 Version:   2.1.300
 Commit:    adab45bf0c

Environnement d'exécution :
 OS Name:     Mac OS X
 OS Version:  10.13
 OS Platform: Darwin
 RID:         osx.10.13-x64
 Base Path:   /usr/local/share/dotnet/sdk/2.1.300/

Host (useful for support):
  Version: 2.1.0
  Commit:  caa7b7e2ba

VS Code version: 1.25.1 C# Extension version: 1.15.2 Ionide-fsharp: 3.23.0 Mono: Mono JIT compiler version 5.4.1.6 (tarball Mon Dec 11 14:59:42 GMT 2017) Visual Studio Community for Mac: 7.5.2 (Build 40)

Steps to reproduce

The exact same steps as #2075 except, it’s on macOS.

Expected behavior

• The Problem window should display no problems for the solution.
• The Editor window should display no problems for Program.cs.

Actual behavior

• The Problem window says, “The name OrderTaking does not exist in the current context.”
• The Editor window underlines the OrderTaking class in Program.cs, with the same error.

Additional informations:

OmniSharp log;

Starting OmniSharp server at 2018-7-26 20:53:45
    Target: /Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Solution.sln

OmniSharp server started
    Path: /Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/run
    PID: 53760

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on MacOS 10.13.6 (x64)
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/MSBuild.dll'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 15.0 - "/Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin"
            MSBuildExtensionsPath = /Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild
            BypassFrameworkInstallChecks = true
            CscToolPath = /Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /Users/salimmakouche/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin
            TargetFrameworkRootPath = /usr/local/Cellar/mono/5.4.1.6/lib/mono/xbuild-frameworks
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Initializing in /Users/salimmakouche/Documents/Projects/dotnet/F/Sydel
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Auto package restore: False
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Update workspace context
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Resolving projects references
[info]: OmniSharp.MSBuild.ProjectSystem
        Detecting projects in '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Solution.sln'.
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel'.
[info]: OmniSharp.Script.ScriptProjectSystem
        Could not find any CSX files
[info]: OmniSharp.Stdio.Host
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpWorkspaceOptionsProvider
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: /Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj
[info]: OmniSharp.Stdio.Host
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel' on host 53738.
[info]: OmniSharp.MSBuild.ProjectManager
        Adding project '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Update project: Sydel.Api.C.Console
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: /Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj
[fail]: OmniSharp.MSBuild.ProjectLoader
        Assets file '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/obj/project.assets.json' doesn't have a target for '.NETCoreApp,Version=v2.0'. Ensure that restore has run and that you have included 'netcoreapp2.0' in the TargetFrameworks for your project.
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'.
/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj
/usr/local/share/dotnet/sdk/2.1.302/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(198,5): Error: Assets file '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/obj/project.assets.json' doesn't have a target for '.NETCoreApp,Version=v2.0'. Ensure that restore has run and that you have included 'netcoreapp2.0' in the TargetFrameworks for your project.

[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/Users/salimmakouche/Documents/Projects/dotnet/F/Sydel/Sydel.Api.C.Console/Sydel.Api.C.Console.csproj'

Errors marked But it compile just like normal.

If you need any further information ? Thank you.

[ghost]

Is there a reason mono-devel is needed for projects that are only using the latest dotnet sdk? Is dotnet sdk missing the API’s to build projects?

[DustinCampbell]

Oh. I see the problem now. The issue is that OmniSharp only includes enough MSBuild logic to handle C# projects. So, when OmniSharp’s standalone MSBuild is used, F# isn’t supported:

[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/dansowter/.vscode-insiders/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin"

Try installing the latest mono-devel package to get more robust MSBuild support: https://www.mono-project.com/download/stable/#download-lin.