# F# language server **URL:** \ **Category:** General\ **Tags:** editorsupport\ **Created:** [June 3, 2018, 5:21pm UTC](https://forums.fsharp.org/t/f-language-server/275 "2018-06-03T17:21:07Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![georgewfraser](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@georgewfraser](https://forums.fsharp.org/u/georgewfraser)\ **Post date:** [June 3, 2018, 5:21pm UTC](https://forums.fsharp.org/t/f-language-server/275/1 "2018-06-03T17:21:07Z")
I want to share something I’ve been working on for a while: a language-server-protocol implementation for F# [https://marketplace.visualstudio.com/items?itemName=georgewfraser.fsharp-language-server](https://marketplace.visualstudio.com/items?itemName=georgewfraser.fsharp-language-server) For those who don’t know it, the language server protocol is a standard JSON-RPC mechanism for editors to talk to code-intelligence implementations. It originated with VSCode, but is now supported by Vim, Emacs, and many others. The LSP is pretty similar to the F# Compiler Service API, so my implementation is essentially a shim between the two protocols. My major goal was high-performance, and its been working great for me, even on large projects. If you’re a VSCode user, please give it a try and raise issues if you have trouble! If you’re a Vim or Emacs user, I would really appreciate it if someone would write instructions for how to install it in these editors and raise a PR. ---
**Author:** ![isaacabraham](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/isaacabraham/32/52_2.png) [@isaacabraham](https://forums.fsharp.org/u/isaacabraham)\ **Post date:** [June 4, 2018, 7:56am UTC](https://forums.fsharp.org/t/f-language-server/275/2 "2018-06-04T07:56:32Z")
Hi George. This looks interesting! Unfortunately I’ve run into a problem when installing it: on opening a folder with some projects in it, I get the following error: ``` Listening on stdin Add workspace root c:\Users\Isaac\Source\Repos\SAFE-Dojo Creating project options for script build.fsx Exception in language server System.Exception: Failed to load PseudoScript.fsproj: The path c:\Users\georgefraser\Documents\fsharp-language-server\client\PseudoScript.fsproj could not be found. ``` Any ideas how to fix this? ---
**Author:** ![georgewfraser](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@georgewfraser](https://forums.fsharp.org/u/georgewfraser)\ **Post date:** [June 4, 2018, 4:25pm UTC](https://forums.fsharp.org/t/f-language-server/275/3 "2018-06-04T16:25:16Z")
Whoops, an absolute path snuck in there! Just published a fix, please update. ---
**Author:** ![mchean](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/mchean/32/209_2.png) [@mchean](https://forums.fsharp.org/u/mchean)\ **Post date:** [June 4, 2018, 6:17pm UTC](https://forums.fsharp.org/t/f-language-server/275/4 "2018-06-04T18:17:13Z")
That is so cool! It will be real helpful in learning F#. Thank you ---
**Author:** ![isaacabraham](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/isaacabraham/32/52_2.png) [@isaacabraham](https://forums.fsharp.org/u/isaacabraham)\ **Post date:** [June 4, 2018, 9:27pm UTC](https://forums.fsharp.org/t/f-language-server/275/5 "2018-06-04T21:27:58Z")
Now I get this: ```auto Listening on stdin Add workspace root c:\Users\Isaac\Source\Repos\tachyus Creating project options for script foobar.fsx Looking for PsuedoScript.fsproj relative to C:\Users\Isaac\.vscode\extensions\georgewfraser.fsharp-language-server-0.1.3\src\FSharpLanguageServer\bin\Release\netcoreapp2.0\win10-x64\publish\ProjectCracker.dll Cancelling request 1 Build started 04/06/2018 23:26:12. __________________________________________________ Project "C:\Users\Isaac\.vscode\extensions\georgewfraser.fsharp-language-server-0.1.3\client\PseudoScript.fsproj" (Compile target(s)): Target GenerateTargetFrameworkMonikerAttribute: Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files. Target GetAssemblyVersion: C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: The "GetAssemblyVersion" task failed unexpectedly. C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: System.IO.FileNotFoundException: Could not load file or assembly 'NuGet.Versioning, Version=4.7.0.5, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. The system cannot find the file specified. C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: File name: 'NuGet.Versioning, Version=4.7.0.5, Culture=neutral, PublicKeyToken=31bf3856ad364e35' C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.NET.Build.Tasks.GetAssemblyVersion.ExecuteCore() C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.NET.Build.Tasks.TaskBase.Execute() C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() in E:\A\_work\82\s\src\Build\BackEnd\TaskExecutionHost\TaskExecutionHost.cs:line 631 C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder.d__25.MoveNext() in E:\A\_work\82\s\src\Build\BackEnd\Components\RequestBuilder\TaskBuilder.cs:line 787 C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: Done building target "GetAssemblyVersion" in project "PseudoScript.fsproj" -- FAILED. Done building project "PseudoScript.fsproj" -- FAILED. Build FAILED. C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: The "GetAssemblyVersion" task failed unexpectedly. C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: System.IO.FileNotFoundException: Could not load file or assembly 'NuGet.Versioning, Version=4.7.0.5, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. The system cannot find the file specified. C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: File name: 'NuGet.Versioning, Version=4.7.0.5, Culture=neutral, PublicKeyToken=31bf3856ad364e35' C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.NET.Build.Tasks.GetAssemblyVersion.ExecuteCore() C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.NET.Build.Tasks.TaskBase.Execute() C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() in E:\A\_work\82\s\src\Build\BackEnd\TaskExecutionHost\TaskExecutionHost.cs:line 631 C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder.d__25.MoveNext() in E:\A\_work\82\s\src\Build\BackEnd\Components\RequestBuilder\TaskBuilder.cs:line 787 C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: C:\Program Files\dotnet\sdk\2.1.300\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.GenerateAssemblyInfo.targets(161,5): error MSB4018: 0 Warning(s) 1 Error(s) Time Elapsed 00:00:00.49 Exception in language server System.Exception: Failed to load PseudoScript.fsproj: Object reference not set to an instance of an object. at ProjectCracker.scriptBase@72.Invoke(Unit unitVar) in /Users/georgefraser/Documents/fsharp-language-server/src/ProjectCracker/ProjectCracker.fs:line 81 at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode) at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor) at System.Lazy`1.CreateValue() at FSharpLanguageServer.ProjectManager.analyzeFsx(FileInfo fsx) in /Users/georgefraser/Documents/fsharp-language-server/src/FSharpLanguageServer/ProjectManager.fs:line 100 at FSharpLanguageServer.ProjectManager.ensureAll(FSharpList`1 fs) in /Users/georgefraser/Documents/fsharp-language-server/src/FSharpLanguageServer/ProjectManager.fs:line 178 at .$ProjectManager.AddWorkspaceRoot@186.Invoke(Unit unitVar) in /Users/georgefraser/Documents/fsharp-language-server/src/FSharpLanguageServer/ProjectManager.fs:line 189 at Microsoft.FSharp.Control.AsyncBuilderImpl.callA@522.Invoke(AsyncParams`1 args) --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at Microsoft.FSharp.Control.AsyncBuilderImpl.commit[a](AsyncImplResult`1 res) at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronouslyInCurrentThread[a](CancellationToken token, FSharpAsync`1 computation) at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronously[a](CancellationToken token, FSharpAsync`1 computation, FSharpOption`1 timeout) at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken) at LSP.LanguageServer.connect(FSharpFunc`2 serverFactory, BinaryReader receive, BinaryWriter send) in /Users/georgefraser/Documents/fsharp-language-server/src/LSP/LanguageServer.fs:line 213 at FSharpLanguageServer.Program.main(String[] argv) in /Users/georgefraser/Documents/fsharp-language-server/src/FSharpLanguageServer/Program.fs:line 703 Cancelling request 2 Cancelling request 3 Cancelling request 5 Cancelling request 6 Cancelling request 7 ``` ---
**Author:** ![georgewfraser](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@georgewfraser](https://forums.fsharp.org/u/georgewfraser)\ **Post date:** [June 5, 2018, 3:10am UTC](https://forums.fsharp.org/t/f-language-server/275/6 "2018-06-05T03:10:38Z")
Thanks for sticking with it @isaacabraham, there’s definitely some issues right now reliably analyzing project files. There’s a github issue [here](https://github.com/georgewfraser/fsharp-language-server/issues/2) where @chethusk and I are working on figuring out a strategy that will “just work”, stay tuned. ---
**Author:** ![isaacabraham](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/isaacabraham/32/52_2.png) [@isaacabraham](https://forums.fsharp.org/u/isaacabraham)\ **Post date:** [June 5, 2018, 6:26am UTC](https://forums.fsharp.org/t/f-language-server/275/7 "2018-06-05T06:26:22Z")
Perfect, I’ll follow that repo instead of pasting issues here 🙂 ---
**Author:** ![Scott](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/scott/32/57_2.png) [@Scott](https://forums.fsharp.org/u/Scott)\ **Post date:** [August 5, 2018, 3:27pm UTC](https://forums.fsharp.org/t/f-language-server/275/8 "2018-08-05T15:27:00Z")
@georgewfraser Is this F# Language Server compatible with Ionide? Or do we need to choose to install one or the other extension in VS Code? Also, a comparison of the features of the two extensions might be helpful (unless I’m completely confused). EDIT: By the way, I just found the " How is this project different than [Ionide](https://github.com/ionide)?" section in the docs, but I don’t think it answered my questions at all.