Ensure you have a recent version of VIM

The LSP client plugin requires vim8/neovim. It is best to have atleast vim 8.1 which allows several code intelligence features (auto-complete, error gutter, symbol list etc.) to work in an intuitive manner out of the box.

Install a plugin manager

I have found vim-plug to work nicely with the required plugins. Install is simple following the instructions here

Modify .vimrc file

Your .vimrc file has to be modified to ensure the following

1. Register CWL as a file type
2. Install LSP client for VIM
3. Configure LSP client to run benten-ls when it loads up a CWL document

A minimally functional .vimrc file is given here (explanations at end)

syntax on

au BufNewFile,BufRead *.cwl setlocal ft=cwl

" Specify a directory for plugins
" - For Neovim: ~/.local/share/nvim/plugged
" - Avoid using standard Vim directory names like 'plugin'
call plug#begin('~/.vim/plugged')

" Make sure you use single quotes

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

call plug#end()

inoremap <expr> <Tab> pumvisible() ? "\<C-n>" : "\<Tab>"
inoremap <expr> <S-Tab> pumvisible() ? "\<C-p>" : "\<S-Tab>"
inoremap <expr> <cr> pumvisible() ? "\<C-y>" : "\<cr>"


let g:lsp_log_verbose = 1
let g:lsp_log_file = expand('~/.vim/vim-lsp.log')

if executable('benten-ls')
    au User lsp_setup call lsp#register_server({
        \ 'name': 'cwl',
        \ 'cmd': {server_info->['benten-ls']},
        \ 'whitelist': ['cwl'],
        \ })
endif

Explanation

au BufNewFile,BufRead *.cwl setlocal ft=cwl

This registers CWL as a type. (You can check if this works properly by loading a cwl file and executing :set ft?. Verify that it returns filetype=cwl)

call plug#begin('~/.vim/plugged')
...
call plug#end()

Registers plugins. There are often issues in getting plugins to install the first time round.

You should check if the plugins are loaded and active by doing :PlugStatus I had to do :PlugInstall to ensure the plugins are installed.

Note: If you want CWL syntax highlighting you can try adding Plug 'manabuishii/vim-cwl' From this project: https://github.com/manabuishii/vim-cwl This is not necessary for testing.

if executable('benten-ls')
    au User lsp_setup call lsp#register_server({
        \ 'name': 'cwl',
        \ 'cmd': {server_info->['benten-ls']},
        \ 'whitelist': ['cwl'],
        \ })
endif

This tells vim to look for the executable benten-ls in the path and start it up as a language server when it opens a cwl file.

Checking if it works

After doing this you should be able to load up a CWL file and verify the vim language client AND the CWL language server are running by doing :LspStatus which should return cwl: starting and then cwl: running

Available commands

The available commands are found on the VIM LSP plugin page.

Other options

I have not explored this, but ALE (Asynchronous Lint Engine) also acts as a language client, and so should also be able to be configured to work with Benten.