Omni completion for items without documentation

Under the hood, rescript-editor-analysis.exe returns null instead of an object/dict when a completion item has no documentation. This results in multiple errors in rescript#Complete.

A minimal example with vim-plug and the latest versions of vim-rescript and rescript (tested in VIM 8.2 and in Neovim 0.6.1):

~/.vimrc or ~/.config/nvim/init.vim:

call plug#begin()
Plug 'rescript-lang/vim-rescript'
call plug#end()

set omnifunc=rescript#Complete
set completeopt+=preview

Example.res:

let myInteger = 1
let myString = "2"

Also needed:

• complete/completion mismatch fix: #56

Make sure the project is built. Type let my as the last line of Example.res and hit <C-x><C-o> in insert mode. You'll get the following errors twice:

Error detected while processing function rescript#Complete:
line   36:
E121: Undefined variable: value
Press ENTER or type command to continue
Error detected while processing function rescript#Complete:
line   38:
E121: Undefined variable: entry
Press ENTER or type command to continue
Error detected while processing function rescript#Complete:
line   38:
E116: Invalid arguments for function add(l:ret, entry)
Press ENTER or type command to continue

After hitting ENTER enough times:

-- Omni completion (^O^N^P) Pattern not found

I think the problem lies here:

https://github.com/rescript-lang/vim-rescript/blob/faeeb2deef1ad0ec67fc892ceeb9949f3bf2d77c/autoload/rescript.vim#L369

item.documentation is null for undocumented matches.

I tried to replace the offending line with the following, and now omni completion works both for built-in items and for undocumented local items (but I'm no expert in vimscript, so this may be a silly way to do it):

    if type(item.documentation) == v:t_dict
      let l:info = item.documentation.value
    else
      let l:info = item.detail " or some default value
    endif

    let entry = { 'word': item.label, 'kind': l:kind, 'info': l:info }

Start in autoload/rescript.vim around line 369 and build the project before reproducing the completion case from the issue in Vim or Neovim. Check the handling of item.documentation when it is null, with the completion mismatch fix in #56 as context. Done means built-in and undocumented local items complete without the reported errors.