OmniSharp crashing - I think there must have been some update causing this issue.

I think there must have been a bug in some of the recent updates causing the following issue. Since two days OmniSharp behaves very strange. It occurs randomly, but often. After I edit my code:

1. Syntax highlighting gets broken, parts of the code stay in default color, sometimes even half a word stay highlighted correctly and the rest loses resets to default color.
2. Problems panel lists many extra errors that are just a fiction. I have to run dotnet build in the terminal to find the true errors.

For example, I changed a declaration of a HashSet<Shape> to a List<Shape>. The following error appeared: The type or namespace name 'HistashSet<>' could not be found (are you missing a using directive or an assembly reference?) and it stays being shown even after half an hour. Some issue must have occurred while I was typing and the code is not re-analyzed anymore. Further fictitious errors occur everywhere I use the respective variable. The syntax highlighting around the edited spot is broken.

The previous example affected just a small portion of the code within just one file. Yesterday I managed to get several hundreds of fictious errors and whole files with over 1k lines all red. It’s impossible to work this way 😢

The following debug information contains also an exception that massively occurs in the OmniSharp log. It is an ArgumentOutOfRange at Microsoft.CodeAnalysis.Text.LinePosition..ctor (System.Int32 line, System.Int32 character) [0x00013] in <74e762f007514b0991a005183ec8dcb2>:0

Environment data

.NET Core SDK (reflecting any global.json):
 Version:   3.1.404
 Commit:    470f6754b3

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  20.04
 OS Platform: Linux
 RID:         ubuntu.20.04-x64
 Base Path:   /usr/share/dotnet/sdk/3.1.404/

Host (useful for support):
  Version: 3.1.10
  Commit:  1721e39439

.NET Core SDKs installed:
  3.1.404 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

C# Extension version: 1.23.5

OmniSharp log

Starting OmniSharp server at 11/11/2020, 10:07:02 PM
    Target: xxx.sln

OmniSharp server started.
    Path: /home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/run
    PID: 7984

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on ubuntu 20.4 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 16.8.0 - "/home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild/Current/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild/Current/Bin/MSBuild.exe'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 16.8.0 - "/home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild/Current/Bin"
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild/Current/Bin
            CscToolPath = /home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild/Current/Bin/Roslyn
            BypassFrameworkInstallChecks = true
            MSBuildExtensionsPath = /home/xxx/.vscode/extensions/ms-dotnettools.csharp-1.23.5/.omnisharp/1.37.3/omnisharp/.msbuild
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/home/xxx'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.MSBuild.ProjectSystem
        Detecting projects in '/home/xxx/xxx.sln'.
[info]: OmniSharp.MSBuild.ProjectManager
...
[fail]: OmniSharp.Stdio.Host
        ************  Response ************ 
{
  "Request_seq": 15,
  "Command": "/v2/highlight",
  "Running": true,
  "Success": false,
  "Message": "\"System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.\\nParameter name: character\\n  at Microsoft.CodeAnalysis.Text.LinePosition..ctor (System.Int32 line, System.Int32 character) [0x00013] in <74e762f007514b0991a005183ec8dcb2>:0 \\n  at OmniSharp.Roslyn.CSharp.Services.SemanticHighlight.SemanticHighlightService.Handle (OmniSharp.Models.SemanticHighlight.SemanticHighlightRequest request) [0x00146] in <8ca5e445b15640a0986680e5a0180b25>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].GetFirstNotEmptyResponseFromHandlers (OmniSharp.Endpoint.Exports.ExportHandler`2[TRequest,TResponse][] handlers, TRequest request) [0x00099] in <9e06207949b04d41ac60c7c691c8ecbb>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].HandleRequestForLanguage (System.String language, TRequest request, OmniSharp.Protocol.RequestPacket packet) [0x00163] in <9e06207949b04d41ac60c7c691c8ecbb>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].Process (OmniSharp.Protocol.RequestPacket packet, OmniSharp.Endpoint.LanguageModel model, Newtonsoft.Json.Linq.JToken requestObject) [0x0024b] in <9e06207949b04d41ac60c7c691c8ecbb>:0 \\n  at OmniSharp.Stdio.Host.HandleRequest (System.String json, Microsoft.Extensions.Logging.ILogger logger) [0x000e7] in <add5f40a6e784fcca3e930b59965388b>:0 \"",
  "Body": null,
  "Seq": 121,
  "Type": "response"
}
[fail]: OmniSharp.Stdio.Host

//This exception repeats many many times.

Steps to reproduce

Unknown, happens randomly at code edits.

Expected behavior

Syntax highlighting should work and there should be no fictitious errors.

Actual behavior

Syntax highlighting broken and plenty of fictitious errors appear.

[vintzl]

Same here: Received response for /v2/getcodeactions but could not find request.

These bugs are very frustrating. Omnisharp is slowing becoming omnishit.

[williamdenton]

I’ve found a possible cause - the project i was working on was not in the sln file, vscode doesn’t care so much about sln, but when there is one, and it’s missing a project, omnisharp appears to be busted.