F# Language Server Updated

This has been forked from GeorgeWfraser's orginal project because that appears to be unmaintained.

It has been updated to support fcs 41 and net6.0 I have used code from FSharpAutoComplete and some adjustments to the original to add some features

• Better hover docs
• working documentation for system types
• semantic tokenization
• support semantic tokens
• Have pretty multiline function signatures in hover docs

I may at some point work on supporting the vim and emacs versions of these extensions but as i use neither, i have not at this time.

My work here is done specificallly in reponse to this issue with ionide here, which makes it unusuable for me and potentially many others. Almost all credit for this should go to georgewfraser and the guys of at FSAC. Really I've mostly just smashed stuff toegther, added glue and fixed some bugs

Now the original descritption

This project is an implementation of the language server protocol using the F# Compiler Service.

Features

Hover

Autocomplete

Method signature help

Find symbols in document

Find symbols in workspace

Go-to-definition

Find references

Rename symbol

Show errors on save

Run & Debug tests

Code structure

The language server protocol (LSP) is very similar to the API defined by the F# compiler service (FCS); most of the implementation is devoted to translating between the types used by FCS and the JSON representation of LSP.

• client/extension.ts: Client-side VSCode launcher
• sample: Example projects used by tests
• scripts: Scripts for building and testing
• src/LSP: Server-side implementation of language server protocol
• src/ProjectCracker: Figures out F# compiler options using Buildalyzer and the MSBuild API.
• src/FSharpLanguageServer: F# language server
• tests/LSP.Tests
• tests/ProjectCracker.Tests
• tests/FSharpLanguageServer.Tests
• videos: Animated GIFs on this page

Installation

VSCode

Install from the VSCode extension marketplace

Clone this repo to your system and build it:

npm install
dotnet build -c Release

If using a distribution based on Arch Linux, you can also install it from the AUR (Still installs the old version) Install LanguageClient-neovim

Update your vim config to point LanguageClient-neovim to the FSharp Language Server for fsharp filetypes:

let g:LanguageClient_serverCommands = {
    \ 'fsharp': ['dotnet', '/Users/name/code/fsharp-language-server/src/FSharpLanguageServer/bin/Release/netcoreapp3.0/target/FSharpLanguageServer.dll']
    \ }

Open an fsharp file, move the cursor, and call functions. Mappings are up to you:

• Hover call LanguageClient#textDocument_hover()
• Rename: call LanguageClient#textDocument_rename()
• Definition: call LanguageClient#textDocument_definition()
• etc...

Neovim with Deoplete completion:

(alternatively there is another vim language server plugin vim-lsp but this one hasn't been tried.

Emacs

Spacemacs

Clone this repo to your system and build it:

npm install

# Pick the appropriate target based upon your OS 
dotnet publish -c Release -r linux-x64 src/FSharpLanguageServer
dotnet publish -c Release -r osx.10.11-x64 src/FSharpLanguageServer
dotnet publish -c Release -r win10-x64 src/FSharpLanguageServer

Make sure that the FSharpLanguageServer (in src/FSharpLanguageServer/bin/Release/netcoreapp3.0/PLATFORM/publish) is in your PATH. Alternatively, you can set the path to the server executable manually within your .spacemacs user-config:

(setq fsharp2-lsp-executable "/path/to/FSharpLanguageServer")

Since the stock fsharp layer does not currently include LSP support, you will need to use the fsharp2 layer (a fork of fsharp) which does. To use fsharp2, copy the custom layer into your Spacemacs private layers directory. In order for this layer to work, you must be on the Spacemacs develop branch, since the LSP layer is not yet available in Spacemacs master.

cp -r spacemacs/fsharp2 ~/.emacs.d/private

Finally, make sure that you have these layers enabled in your dotspacemacs-configuration-layers. You will need to remove the fsharp layer if you have it, since fsharp2 conflicts with it.

• fsharp2
• syntax-checking
• auto-completion

How is this project different than Ionide?

Ionide is a suite of F# plugins for VSCode; F# language server is analagous to the FSAC component.

The implementation is a thin wrapper around F# Compiler Service and is heavily focused on performance. For example, autocompleting in medium-sized file in F# Language Server (left) and Ionide (right):

Contributing

Please do!

Any help is very much appreciated, issues, PR's, even just asking a question about how something works. I'm happy to help and be helped

Building

• npm install to setup node deps (not needed unless you plan to build the vsix extension package)

• dotnet tool restore to install paket

• dotnet paket install to install all dependencies

Then refer to the build scripts.

Essentially you just publish the language server with dotnet publish -c Release src/FSharpLanguageServer then run vsce package -o build.vsix to package it up

If you want to try your newly created extension run code --install-extension build.vsix

You can also change the Fsharp.debug setting in vscode which will cause the installed extension to try to build fslsp when it launches. Very handy for testing many smaller changes without republishing the extension.