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Nim Language Server Protocol

This is a Language Server Protocol implementation in Nim, for Nim. It is based on nimsuggest, which means that every editor that supports LSP will now have the same quality of suggestions that has previously only been available in supported editors.

Installing nimlsp

If you have installed Nim through choosenim (recommended) the easiest way to install nimlsp is to use nimble with:

nimble install nimlsp

This will compile and install it in the nimble binary directory, which if you have set up nimble correctly it should be in your path. When compiling and using nimlsp it needs to have Nims sources available in order to work. With Nim installed through choosenim these should already be on your system and nimlsp should be able to find and use them automatically. However if you have installed nimlsp in a different way you might run into issues where it can't find certain files during compilation/running. To fix this you need to grab a copy of Nim sources and then point nimlsp at them on compile-time by using -d:explicitSourcePath=PATH, where PATH is where you have your Nim sources. You can also pass them at run-time (if for example you're working with a custom copy of the stdlib by passing it as an argument to nimlsp. How exectly to do that will depend on the LSP client.

Compile nimlsp

If you want more control over the compilation feel free to clone the repository. nimlsp depends on the nimsuggest sources which is in the main Nim repository, so make you you have a copy of that somewhere. Manually having a copy of Nim this way means the default source path will not work so you need to set it explicitly on compilation with -d:explicitSourcePath=PATH and point to it on runtime (technically the runtime should only need the stdlib, so omitting it will make nimlsp try to find it from your Nim install).

To do the standard build run:

nimble build

Or if you want debug output when nimlsp is running:

nimble debug

Or if you want even more debug output from the LSP format:

nimble debug -d:debugLogging

Supported Protocol features

Status LSP Command
DONE textDocument/didChange
DONE textDocument/didClose
DONE textDocument/didOpen
DONE textDocument/didSave
☐ TODO textDocument/codeAction
DONE textDocument/completion
DONE textDocument/definition
☐ TODO textDocument/documentHighlight
TODO textDocument/documentSymbol
☐ TODO textDocument/executeCommand
☐ TODO textDocument/format
DONE textDocument/hover
DONE textDocument/rename
DONE textDocument/references
☐ TODO textDocument/signatureHelp
DONE textDocument/publishDiagnostics
☐ TODO workspace/symbol

Setting up nimlsp


First you need a LSP client, the one that's been tested is It's certainly not perfect, but it works well enough.

Once you have it installed you'll want to grab NimLime as well. NimLime can perform many of the same features that nimlsp does, but we're only interested in syntax highlighting and some definitions. If you know how to disable the overlapping features or achieve this in another way please update this section.

Now in order to set up LSP itself enter it's settings and add this:

            "<path to nimlsp>/nimlsp" // This can be changed if you put nimlsp in your PATH
         "enabled": true,
            "PATH": "<home directory>/.nimble/bin" // To be able to find nimsuggest, can be changed if you have nimsuggest in your PATH
         "languageId": "nim",
   // These are mostly for debugging feel free to remove them
   // If you build nimlsp without debug information it doesn't
   // write anything to stderr
   "log_payloads": true,
   "log_stderr": true


To use nimlsp in Vim install the prabirshrestha/vim-lsp plugin and dependencies:

Plugin 'prabirshrestha/asyncomplete.vim'
Plugin 'prabirshrestha/async.vim'
Plugin 'prabirshrestha/vim-lsp'
Plugin 'prabirshrestha/asyncomplete-lsp.vim'

Then set it up to use nimlsp for Nim files:

let s:nimlspexecutable = "nimlsp"
let g:lsp_log_verbose = 1
let g:lsp_log_file = expand('/tmp/vim-lsp.log')
" for asyncomplete.vim log
let g:asyncomplete_log_file = expand('/tmp/asyncomplete.log')

let g:asyncomplete_auto_popup = 0

if has('win32')
   let s:nimlspexecutable = "nimlsp.cmd"
   " Windows has no /tmp directory, but has $TEMP environment variable
   let g:lsp_log_file = expand('$TEMP/vim-lsp.log')
   let g:asyncomplete_log_file = expand('$TEMP/asyncomplete.log')
if executable(s:nimlspexecutable)
   au User lsp_setup call lsp#register_server({
   \ 'name': 'nimlsp',
   \ 'cmd': {server_info->[s:nimlspexecutable]},
   \ 'whitelist': ['nim'],
   \ })

function! s:check_back_space() abort
    let col = col('.') - 1
    return !col || getline('.')[col - 1]  =~ '\s'

inoremap <silent><expr> <TAB>
  \ pumvisible() ? "\<C-n>" :
  \ <SID>check_back_space() ? "\<TAB>" :
  \ asyncomplete#force_refresh()
inoremap <expr><S-TAB> pumvisible() ? "\<C-p>" : "\<C-h>"

This configuration allows you to hit Tab to get auto-complete, and to call various functions to rename and get definitions. Of course you are free to configure this any way you'd like.


With lsp-mode and use-package:

(use-package nim-mode
  :ensure t
  (nim-mode . lsp))


You will need to install the LSP support plugin. For syntax highlighting i would recommend the "official" nim plugin (its not exactly official, but its developed by an intellij dev), the plugin will eventually use nimsuggest and have support for all this things and probably more, but since its still very new most of the features are still not implemented, so the LSP is a decent solution (and the only one really).

To use it:

  1. Install the LSP and the nim plugin.
  2. Go into settings > Language & Frameworks > Language Server Protocol > Server Definitions.
  3. Set the LSP mode to executable, the extension to nim and in the Path, the path to your nimlsp executable.
  4. Hit apply and everything should be working now.

Run Tests

Not too many at the moment unfortunately, but they can be run with:

nimble test


Language Server Protocol implementation for Nim





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