[LSP] Failed to handle notification initialize

[luizribeiro]

I'm working on integrating vim-ale directly with omnisharp-roslyn's LSP server, as omnisharp-vim does not use the LSP as far as I can tell. This is so I can get auto-completion through vim-ale and LSP and not through omnicomplete itself.

In doing so, I've been getting errors back from omnisharp's LSP server. More specifically:

{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":1,"message":"Failed to handle notification initialize - System.NullReferenceException: Object reference not set to an instance of an object\n  at OmniSharp.Extensions.LanguageServer.Server.LanguageServer.OmniSharp.Extensions.Embedded.MediatR.IRequestHandler<OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams,OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeResult>.Handle (OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams request, System.Threading.CancellationToken token) [0x0022d] in <c33e73e38fa14bf293bda2f62d3759c4>:0 \n  at OmniSharp.Extensions.LanguageServer.Server.Pipelines.ResolveCommandPipeline`2[TRequest,TResponse].Handle (TRequest request, System.Threading.CancellationToken cancellationToken, OmniSharp.Extensions.Embedded.MediatR.RequestHandlerDelegate`1[TResponse] next) [0x000e1] in <c33e73e38fa14bf293bda2f62d3759c4>:0 \n  at OmniSharp.Extensions.LanguageServer.Server.LspRequestRouter.RouteRequest (OmniSharp.Extensions.JsonRpc.IHandlerDescriptor descriptor, OmniSharp.Extensions.JsonRpc.Server.Request request) [0x002e2] in <c33e73e38fa14bf293bda2f62d3759c4>:0 "}}Content-Length: 129

{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"Finished: Routing Request (1) initialize in 1000ms"}}Content-Length: 1158

{"jsonrpc":"2.0","id":"1","error":{"code":-32602,"message":"Internal Error - System.NullReferenceException: Object reference not set to an instance of an object\n  at OmniSharp.Extensions.LanguageServer.Server.LanguageServer.OmniSharp.Extensions.Embedded.MediatR.IRequestHandler<OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams,OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeResult>.Handle (OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams request, System.Threading.CancellationToken token) [0x0022d] in <c33e73e38fa14bf293bda2f62d3759c4>:0 \n  at OmniSharp.Extensions.LanguageServer.Server.Pipelines.ResolveCommandPipeline`2[TRequest,TResponse].Handle (TRequest request, System.Threading.CancellationToken cancellationToken, OmniSharp.Extensions.Embedded.MediatR.RequestHandlerDelegate`1[TResponse] next) [0x000e1] in <c33e73e38fa14bf293bda2f62d3759c4>:0 \n  at OmniSharp.Extensions.LanguageServer.Server.LspRequestRouter.RouteRequest (OmniSharp.Extensions.JsonRpc.IHandlerDescriptor descriptor, OmniSharp.Extensions.JsonRpc.Server.Request request) [0x002e2] in <c33e73e38fa14bf293bda2f62d3759c4>:0 "}}

In other words, this is the exception that omnisharp-roslyn is giving me during initialization:

System.NullReferenceException: Object reference not set to an instance of an object
  at OmniSharp.Extensions.LanguageServer.Server.LanguageServer.OmniSharp.Extensions.Embedded.MediatR.IRequestHandler<OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams,OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeResult>.Handle (OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams request, System.Threading.CancellationToken token) [0x0022d] in <c33e73e38fa14bf293bda2f62d3759c4>:0 
  at OmniSharp.Extensions.LanguageServer.Server.Pipelines.ResolveCommandPipeline`2[TRequest,TResponse].Handle (TRequest request, System.Threading.CancellationToken cancellationToken, OmniSharp.Extensions.Embedded.MediatR.RequestHandlerDelegate`1[TResponse] next) [0x000e1] in <c33e73e38fa14bf293bda2f62d3759c4>:0 
  at OmniSharp.Extensions.LanguageServer.Server.LspRequestRouter.RouteRequest (OmniSharp.Extensions.JsonRpc.IHandlerDescriptor descriptor, OmniSharp.Extensions.JsonRpc.Server.Request request) [0x002e2] in <c33e73e38fa14bf293bda2f62d3759c4>:0

For reference, this seems to be the command that vim-ale is sending to initialize the LSP:

{"method": "initialize", "jsonrpc": "2.0", "id": 1, "params": {"initializationOptions": {}, "rootUri": "file:///Users/luiz/projects/mgsb", "capabilities": {}, "rootPath": "/Users/luiz/projects/mgsb", "processId": 28524}}

Any idea what's up?

[bjorkstromm]

@luizribeiro I think this is most likely because you don't send any client capabilities in your initialization request. Try to add at least support for text synchronization in your client implementation.

[luizribeiro]

Thanks @mholo65, you are right! Looks like vim-ale doesn't send any capabilities because of a TODO that was left behind:

https://github.com/w0rp/ale/blob/3b7c86e401eb488acd8713f7c9ee81344095080d/autoload/ale/lsp/message.vim#L32-L40

Aren't all these fields optional on the LSP spec?

LSP should announce the capabilities it supports, but this is the first server I encounter that doesn't work with vim-ale because of this.

Either way, sending this as the capabilities made me get past the initialize message:

{  
   "workspace":{},
   "textDocument":{  
      "completion":{  
         "completionItem":{  
            "snippetSupport":false
         }
      }
   }
}

When I tried sending the text synchronization, I ran into #1403.

[w0rp]

Some capabilities are now sent by ALE, but you should also allow clients to connect to the server without sending any capabilities. All of the keys are optional.

[bjorkstromm]

@w0rp yes, that’s a bug in the LSP implementation we are using. We are currently seeing other issues regarding initialization (and capabilities) and will put this on the list of things to do. //cc @david-driscoll

[bjorkstromm]

Tracking fix here OmniSharp/csharp-language-server-protocol#141

[david-driscoll]

This should be fixed via OmniSharp/csharp-language-server-protocol#147

[rcjsuen]

Just got hit by this using omnisharp-mono.tar.gz from v1.34.0. I guess the fix hasn't been incorporated here yet.

I worked around it by adding "workspace": {} to my request. Thank you @luizribeiro for sharing your code.

[luizribeiro]

I'm pretty sure we can close this. I've been using omnisharp-roslyn successfully with vim-ale.

Thanks for all your work on this!