Minimal vimrc to reproduce problem with ncm2 and neosnippets

minimal.vimrc

"" vim:fdm=expr:fdl=0
"" vim:fde=getline(v\:lnum)=~'^"#'?'>'.(matchend(getline(v\:lnum),'"#*')-1)\:'='

if has('nvim')
    set runtimepath+=~/.vim,~/.vim/after
    set packpath+=~/.vim
endif

"# Standard boilerplate

set nocompatible              " be iMproved, required
filetype off                  " required
syntax on "enable syntax highlighting

"# vim-plug

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

"## rust support

Plug 'rust-lang/rust.vim'
let g:rustfmt_autosave = 1 " automatically rustfmt on save

"## LanguageClient-neovim LSP support

" LSP client for those languages that provide a language server
Plug 'autozimu/LanguageClient-neovim', {
    \ 'branch': 'next',
    \ 'do': 'bash install.sh',
    \ }
" TODO: add other languages' LSP configs here over time, and make sure if you add other languages here that you disable
" ALE linters above so they don't step on each other
let g:LanguageClient_serverCommands = {
    \ 'rust': ['rustup', 'run', 'nightly', 'rls']
    \ }

"## ncm2 autocompleter (replaces deoplete)

Plug 'ncm2/ncm2'
Plug 'roxma/nvim-yarp'

" enable ncm2 for all buffers
autocmd BufEnter * call ncm2#enable_for_buffer()

" Use two different sets of completeop values: one for Ncm2PopupOpen, and the
" other when neovim's built-in completion is being used (like the command
" line)
au User Ncm2PopupOpen set completeopt=noinsert,menuone,noselect
au User Ncm2PopupClose set completeopt=menuone

" suppress the annoying 'match x of y', 'The only match' and 'Pattern not
" found' messages
set shortmess+=c

"### Completion source plugins

" NOTE: you need to install completion sources to get completions. Check
" our wiki page for a list of sources: https://github.com/ncm2/ncm2/wiki
"
" I have not included any of the language-specific completion plugins.  They
" exist for just about every popular language, but right now I'm working with
" langauges that have LSP support which is obviously going to be much richer.
" Down the road it may be necessary to bring in some language support if LSP
" is lacking.
Plug 'ncm2/ncm2-bufword' " any word that appears in the current buffer

"### Other ncm2-related plugins

Plug 'ncm2/ncm2-neosnippet'  " integrate with neosnippet for snippet autocompletion

"## neosnippet for snippets

" I used to use Ultisnips but switched to neosnippet because it integrates
" with deoplete.  Maybe Ultisnips does too by now but I am happy with it as it
" is.
Plug 'Shougo/neosnippet.vim'      " the snippet plugin itself
Plug 'Shougo/context_filetype.vim' " another plugin which detects the filetype at the cursor for complex files
Plug 'Shougo/neosnippet-snippets' " a default collection of snippets
imap <C-k>     <Plug>(neosnippet_expand_or_jump)
smap <C-k>     <Plug>(neosnippet_expand_or_jump)
xmap <C-k>     <Plug>(neosnippet_expand_target)

" Press enter key to trigger snippet expansion
" The parameters are the same as `:help feedkeys()`
inoremap <silent> <expr> <CR> ncm2_neosnippet#expand_or("\<CR>", 'n')

func! TabPressed()
  echom "TabPressed"

  echom "neosnippet#expandable_or_jumpable(): " . neosnippet#expandable_or_jumpable()
  echom "pumvisible(): ". pumvisible()
  echom "ncm2_neosnippet#completed_is_snippet(): " . ncm2_neosnippet#completed_is_snippet()
  echom "Completed item:"
  echom json_encode(v:completed_item)

  if ncm2_neosnippet#completed_is_snippet()
    "return "\<Plug>(ncm2_neosnippet_expand_completed)"
    "return "\<Plug>(neosnippet_expand_or_jump)"
    "call feedkeys("\<Plug>(neosnippet_expand_or_jump)", "im")
    return "\<C-k>"
  elseif pumvisible()
    return "\<C-n>"
  else
    return "\<TAB>"
  endif
endfunction

" SuperTab like snippets behavior.  I want this to work whether a popup is
" currently displayed or not.
" Note: It must be "imap" and "smap".  It uses <Plug> mappings.
imap <expr><TAB> TabPressed()
  \ ncm2_neosnippet#completed_is_snippet() ? "\<Plug>(ncm2_neosnippet_expand_completed)" :
  \ pumvisible() ? "\<C-n>" : "\<TAB>"

"## end plugins
" Add plugins to &runtimepath
call plug#end()