nvim: Improve lsp source chaining

Lsp will by default invoke most of its sources simultaneously (one after
the other if no completions are found for the first), but this is
disabled for pandoc.

In pandoc, only the buffer and lsp sources are invoked (the first
chain), since bibcite will take a while to compile the cite keys.
To invoke bibcite in pandoc, use c-j/c-k when in the completion menu,
and they will be calculated.

This may be removed if a faster compilation for bibtex citekeys is
found.

nvim/.config/nvim/plugin/completion-nvim.vim

@@ -2,13 +2,12 @@
 autocmd BufEnter * lua require'completion'.on_attach()
 
 "map <c-p> to manually trigger completion
-imap <silent> <c-p> <Plug>(completion_trigger)
-imap <silent> <c-n> <Plug>(completion_trigger)
-
-" Add <Tab> and <S-Tab> to navigate through popup menu
-inoremap <expr> <Tab>   pumvisible() ? "\<C-n>" : "\<Tab>"
-inoremap <expr> <S-Tab> pumvisible() ? "\<C-p>" : "\<S-Tab>"
-
+imap <silent> <c-n> <Plug>(completion_smart_tab)
+imap <silent> <c-p> <Plug>(completion_smart_s_tab)
+" switch between completion sources manually with c-j/c-k
+" only do so if popupmenu is visible, otherwise normal function
+imap <silent> <c-j> <Plug>(completion_next_source)
+imap <silent> <c-k> <Plug>(completion_previous_source)
 
 " Set completeopt to have a better completion experience
 set completeopt=menuone,noinsert,noselect
@@ -22,38 +21,49 @@ let g:completion_matching_strategy_list = ['exact', 'substring', 'fuzzy']
 " even when backtracking enable completion
 let g:completion_trigger_on_delete = 1
 
+" switch between different completion changes when no completions found for
+" current one
+let g:completion_auto_change_source = 1
+
 " register new completion engines
 " (set in rtp/lua/*_complete.lua)
 "
 " pandoc citation key completion
 lua require'completion'.addCompletionSource('bibcite', require'pandoc_complete'.complete_item)
 
-" only call for specified shortcut, or with completion keys
+" in pandoc files, normal completion should only come from buffer sources and
+" bibcite only invoked manually, since it takes long to parse
 augroup pandocCompletion
-    autocmd!
-    autocmd BufEnter * call SetupPandocCompletion()
+  autocmd!
+  autocmd BufEnter * call SetupPandocCompletion()
 augroup end
 fun! SetupPandocCompletion()
-    if &ft =~ 'pandoc'
-        let g:completion_enable_auto_popup = 0
-        let g:completion_trigger_character = ['@\w*']
-        return
-    endif
-    let g:completion_enable_auto_popup = 1
-    let g:completion_trigger_character = ['.']
+  if &ft =~ 'pandoc'
+    let g:completion_auto_change_source = 1
+    return
+  endif
+  let g:completion_auto_change_source = 0
 endfun
 
 " the completion chains for different filetypes
 " see https://github.com/nvim-lua/completion-nvim/wiki/chain-complete-support
 let g:completion_chain_complete_list = {
     \ 'pandoc': [
-    \    {'complete_items': ['bibcite', 'lsp', 'snippet']},
-    \    {'mode': '<c-p>'},
-    \    {'mode': '<c-n>'}
+    \    { 'complete_items': ['buffer',  'lsp', 'snippet']},
+    \    { 'complete_items': ['bibcite'] },
+    \    { 'mode': '<c-p>'},
+    \    { 'mode': '<c-n>'}
+    \],
+    \ 'tex': [
+    \    { 'complete_items': ['buffer',  'lsp', 'snippet']},
+    \    { 'complete_items': ['bibcite'] },
+    \    { 'mode': '<c-p>'},
+    \    { 'mode': '<c-n>'}
     \],
     \ 'default': [
-    \    {'complete_items': ['lsp', 'snippet']},
-    \    {'mode': '<c-p>'},
-    \    {'mode': '<c-n>'}
+    \    { 'complete_items': ['lsp', 'snippet']},
+    \    { 'complete_items': [ 'buffers' ] },
+    \    { 'mode': '<c-p>'},
+    \    { 'mode': '<c-n>'}
     \]
 \}

nvim/.config/nvim/plugin/nvim-lspconfig.vim

@@ -1,4 +1,9 @@
-
 " enable python language servers
 lua require'nvim_lsp'.pyls.setup{}
 lua require'nvim_lsp'.vimls.setup{}
+lua require'nvim_lsp'.bashls.setup{}
+lua require'nvim_lsp'.gopls.setup{}
+lua require'nvim_lsp'.texlab.setup{}
+
+" requires manual `:LspInstall sumneko_lua`
+lua require'nvim_lsp'.sumneko_lua.setup{}