Add ALE backend support

[cannorin]

Related: #5
Refs:

• Document how to add your own LSP connections better dense-analysis/ale#2641
• https://github.com/dense-analysis/ale/blob/master/autoload/ale/lsp.vim

[cannorin]

memo:

• ale#lsp#CreateMessageData -(message data)-> ale#lsp#Send
• ale#lsp#RegisterCallback

[dhilst]

Hi, I would like to help on this! :) Is there any work in progress?

-- Edit --

I could get a basic support with this code

function! Fsharp_callback(bufnr, lines) abort
  " output example: Program.fs(7,5,7,9):FSharpLint warning FL0038: Consider changing `path` to PascalCase.
  let pattern = '\([^(]\+\)(\(\d\+\),\(\d\+\),\(\d\+\),\(\d\+\)):FSharpLint \(\w\+\) \(.*\)$'
  let lines = a:lines[1:-2]
  let result = []
  for line in lines
    let matches = matchlist(line, pattern)
    if len(matches) >= 7
      if matches[6] == 'error'
        let type = 'E'
      else
        let type = 'W'
      end
      let element = {
            \ 'text': matches[7],
            \ 'detail': matches[7],
            \ 'lnum':  matches[2],
            \ 'col': matches[3],
            \ 'end_lnum': matches[4],
            \ 'end_col': matches[5],
            \ 'filename': fnamemodify(matches[1], ':p'),
            \ 'type': type
            \ }
      call add(result, element)
    endif
  endfor
  return result
endfun

call ale#linter#Define('fsharp', {
\   'name': 'FSharpLint',
\   'alias': ['fsharplint'],
\   'executable': 'dotnet',
\   'command': '%e fsharplint --format msbuild lint %t',
\   'callback': 'Fsharp_callback',
\   'lint_file': 1,
\ })

But I'm not very help with it, it depends on files being written to disk and do it's not using LSP, I will try adding an LSP version, but then I would not use dotnet fsharplint at all right? Once I got things more structured I open a PR :)

Great project by the way :-)

-- Edit --

I tested this approach better a it's terribly slow, I don't know if this because the dotnet fsharplint is slow to start or if it's because of disk I/O, I'm betting that the first is the worse problem.

Anyway, I couldn't find a LanguageClient_serverComands line for FsautoComplete anywhere so I don't really know what it would be, I searched in the readme and in your dotfiles/.vimr. Are you using FsharpAutoComplete as LSP server? In theory it would be possible to get all FsharpAutoComplete features without ALE dont? Just LanguageClient_neovim would be enough

-- Edit --

Okay I got it, it was not easy to find out but here is what worked for me

let g:LanguageClient_serverCommands = {
    \ 'fsharp': ['dotnet', expand('~/.vim/plugged/Ionide-vim/fsac/fsautocomplete.dll')]
    \ }

[cannorin]

@dhilst Hi, thank you very much for your work! I'm failing to take the time to improve Ionide-vim, so I don't have any WIP on this. It will help me a lot if you could improve it and make a PR!

[dhilst]

@cannorin Hello, no problem I have some spare time at weekends, I will try add ALE support, once I got something working I open a PR so you can review.

Cheers