Suptertab chaining is not working with neovim LSP

[sblask]

I set up Neovim's LSP following the guide here: https://github.com/neovim/nvim-lspconfig the relevant bit being this:

local on_attach = function(client, bufnr)
  -- Enable completion triggered by <c-x><c-o>
  vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc')

There are two problems with it. Because the omnifunc is only set when the LSP attaches, the autocmd to configure SuperTab:

  autocmd FileType *
    \ if &omnifunc != '' |
    \   call SuperTabChain(&omnifunc, "<c-p>") |
    \ endif

for setting up the chaining doesn't work because when it's executed omnifunc is still empty.

But even if I change it to:

  autocmd FileType * call SuperTabChain(&omnifunc, "<c-p>")

I get errors:

=SuperTab('n')
Error detected while processing function SuperTabCodeComplete:
line   12:
E15: Invalid expression: v:lua
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   12:
E475: Invalid argument: v:lua.vim.lsp.omnifunc
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   15:
E117: Unknown function: Func
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   16:
E121: Undefined variable: start
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   12:
E15: Invalid expression: v:lua
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   12:
E475: Invalid argument: v:lua.vim.lsp.omnifunc
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   23:
E117: Unknown function: Func
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   26:
E121: Undefined variable: results
Press ENTER or type command to continue
Error detected while processing function SuperTabCodeComplete:
line   26:
E116: Invalid arguments for function type
Press ENTER or type command to continue
Scanning tags.
Press ENTER or type command to continue

Is there anything I can do or can SuperTab be changed to make this work?

[jparoz]

+1 for this from me, same issue precisely. I might have a poke around in Supertab in the next week or two to try to figure out a fix.

Edit: I ended up switching to mucomplete, so I won't be looking any further on this.

[ddickstein]

This happens because SuperTabCodeComplete has the line:

let Func = function(b:SuperTabChain[0])

which makes a funcref out of b:SuperTabChain[0], and the docs for v:lua explicitly say:

Note: v:lua without a call is not allowed in a Vimscript expression: Funcrefs cannot represent Lua functions.

You can work around this with the following:

vim.cmd [[
  function! SuperTabLspOmnifunc(findstart, base)
    return v:lua.vim.lsp.omnifunc(a:findstart, a:base)
  endfunction
]]
vim.bo.omnifunc = "SuperTabLspOmnifunc"
-- Reactivate completion chaining after setting omnifunc (see `:h supertab-completionchaining`)
vim.fn.SuperTabChain("SuperTabLspOmnifunc", "<c-p>")
vim.fn.SuperTabSetDefaultCompletionType("<c-x><c-u>")