Intellisense doesn't work Manjaro

Environment data

dotnet --info output:

NET Command Line Tools (2.1.105)

Product Information:
 Version:            2.1.105
 Commit SHA-1 hash:  141cc8d976

Runtime Environment:
 OS Name:     manjaro
 OS Version:  
 OS Platform: Linux
 RID:         linux-x64
 Base Path:   /opt/dotnet/sdk/2.1.105/

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.7
  Build    : 2d61d0b043915bc948ebf98836fefe9ba942be11

VS Code version: 1.23.1

C# Extension version: 1.15.0

Steps to reproduce

Default run of Unity project.

Expected behavior

Intellisense worked

Actual behavior

Starting OmniSharp server at 5/18/2018, 1:20:22 PM
    Target: /home/ideo/Documents/workspace_unity/Guardian/Guardian/Guardian.sln

OmniSharp server started with Mono 5.10.1
    Path: /home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/OmniSharp.exe
    PID: 6441

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on manjaro 0.0 (x64)
[warn]: OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider
        It looks like you have Mono 5.2.0 or greater installed but MSBuild could not be found.
Try installing MSBuild into Mono (e.g. 'sudo apt-get install msbuild') to enable better MSBuild support.
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/ideo/.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 '/home/ideo/.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 - "/home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin"
            MSBuildExtensionsPath = /usr/lib/mono/xbuild
            BypassFrameworkInstallChecks = true
            CscToolPath = /home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin
            TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/home/ideo/Documents/workspace_unity/Guardian/Guardian'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Initializing in /home/ideo/Documents/workspace_unity/Guardian/Guardian
[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 '/home/ideo/Documents/workspace_unity/Guardian/Guardian/Guardian.sln'.
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/home/ideo/Documents/workspace_unity/Guardian/Guardian/Assembly-CSharp.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/home/ideo/Documents/workspace_unity/Guardian/Guardian/Assembly-CSharp-Editor.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/home/ideo/Documents/workspace_unity/Guardian/Guardian'.
[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.Stdio.Host
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location '/home/ideo/Documents/workspace_unity/Guardian/Guardian' on host 6349.
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: /home/ideo/Documents/workspace_unity/Guardian/Guardian/Assembly-CSharp.csproj
[warn]: OmniSharp.MSBuild.ProjectLoader
        Unable to create directory "/Debug/". Access to the path "/Debug/" is denied.
[warn]: OmniSharp.MSBuild.ProjectLoader
        Could not write state file "/Debug/Assembly-CSharp.csprojResolveAssemblyReference.cache". Could not find a part of the path "/Debug/Assembly-CSharp.csprojResolveAssemblyReference.cache".
[fail]: OmniSharp.MSBuild.ProjectLoader
        Could not write lines to file "/Debug/Assembly-CSharp.csproj.CoreCompileInputs.cache". Could not find a part of the path "/Debug/Assembly-CSharp.csproj.CoreCompileInputs.cache".
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/home/ideo/Documents/workspace_unity/Guardian/Guardian/Assembly-CSharp.csproj'.
/home/ideo/Documents/workspace_unity/Guardian/Guardian/Assembly-CSharp.csproj
/home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/Microsoft.Common.CurrentVersion.targets(1089,5): Error: Unable to create directory "/Debug/". Access to the path "/Debug/" is denied.
/home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/Microsoft.Common.CurrentVersion.targets(2067,5): Error: Could not write state file "/Debug/Assembly-CSharp.csprojResolveAssemblyReference.cache". Could not find a part of the path "/Debug/Assembly-CSharp.csprojResolveAssemblyReference.cache".
/home/ideo/.vscode/extensions/ms-vscode.csharp-1.15.2/.omnisharp/1.30.1/omnisharp/msbuild/15.0/Bin/Microsoft.Common.CurrentVersion.targets(3387,5): Error: Could not write lines to file "/Debug/Assembly-CSharp.csproj.CoreCompileInputs.cache". Could not find a part of the path "/Debug/Assembly-CSharp.csproj.CoreCompileInputs.cache".

[DustinCampbell]

Great! Glad to hear it!

[DustinCampbell]

IIRC, Manjaro is based on Arch and the Mono package does not include Mono’s version of MSBuild. Try installing the https://aur.archlinux.org/packages/msbuild-stable/ package.