Error with neco-vim on Vim where many functions exist

[statiolake]

Warning: I will close the issue without the minimal init.vim and the reproduction instructions.

Problems summary

When there're a lot of functions registered in Vim, triggering completion causes error Failed to parse received text '...': Syntax Error: Unexpected token i in JSON at position 65540. (Actually '...' is received JSON. The position or exact error message may differ, but error position is around 65000-. The shown received JSON seems incomplete.)

Expected

ddc.vim normally shows completion list.

Environment Information

• ddc version (SHA1): 80c5f2e

• OS: Windows 10 20H2 19042.1165

• neovim/Vim :version output:

VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Aug 15 2021 22:20:28)
MS-Windows 64 ビット GUI 版
適用済パッチ: 1-3350
Compiled by dicen@THUNDERBOLT
Huge 版 with GUI.  機能の一覧 有効(+)/無効(-)
+acl                +cursorbind         +iconv/dyn          -mzscheme           -sodium             +vartabs
+arabic             +cursorshape        +insert_expand      +netbeans_intg      +sound              +vertsplit
+autocmd            +darkmode_w32       +ipv6               +num64              +spell              +virtualedit
+autochdir          +dialog_con_gui     +job                -ole                +startuptime        +visual
+autoservername     +diff               +jumplist           +packages           +statusline         +visualextra
+balloon_eval       +digraphs           +keymap             +path_extra         -sun_workshop       +viminfo
-balloon_eval_term  +directx            +lambda             -perl               +syntax             +vreplace
+browse             -dnd                +langmap            +persistent_undo    +tag_binary         -vtp
++builtin_terms     -ebcdic             +libcall            +popupwin           -tag_old_static     +wildignore
+byte_offset        +emacs_tags         +linebreak          -postscript         -tag_any_white      +wildmenu
+channel            +eval               +lispindent         +printer            -tcl                +windows
+cindent            +ex_extra           +listcmds           +profile            -termguicolors      +writebackup
+clientserver       +extra_search       +localmap           -python             +terminal           -xfontset
+clipboard          -farsi              +lua/dyn            +python3/dyn        -termresponse       -xim
+cmdline_compl      +file_in_path       +menu               +quickfix           +textobjects        +xpm_w32
+cmdline_hist       +find_in_path       +mksession          +reltime            +textprop           -xterm_save
+cmdline_info       +float              +modify_fname       +rightleft          -tgetent            
+comments           +folding            +mouse              -ruby               +timers             
+conceal            -footer             +mouseshape         +scrollbind         +title              
+cryptv             +gettext/dyn        +multi_byte_ime/dyn +signs              +toolbar            
+cscope             -hangul_input       +multi_lang         +smartindent        +user_commands      
      システム vimrc: "$VIM\vimrc"
      ユーザー vimrc: "$HOME\_vimrc"
   第2ユーザー vimrc: "$HOME\vimfiles\vimrc"
   第3ユーザー vimrc: "$VIM\_vimrc"
       ユーザー exrc: "$HOME\_exrc"
    第2ユーザー exrc: "$VIM\_exrc"
     システム gvimrc: "$VIM\gvimrc"
     ユーザー gvimrc: "$HOME\_gvimrc"
  第2ユーザー gvimrc: "$HOME\vimfiles\gvimrc"
  第3ユーザー gvimrc: "$VIM\_gvimrc"
  デフォルトファイル: "$VIMRUNTIME\defaults.vim"
    システムメニュー: "$VIMRUNTIME\menu.vim"
コンパイル: cl -c /W3 /GF /nologo  -I. -Iproto -DHAVE_PATHDEF -DWIN32  -DFEAT_CSCOPE -DFEAT_TERMINAL -DFEAT_SOUND -DFEAT_NETBEANS_INTG -DFEAT_JOB_CHANNEL -DFEAT_IPV6   -DFEAT_XPM_W32    -DFEAT_DARKMODE_W32   -DWINVER=0x0501 -D_WIN32_WINNT=0x0501 /source-charset:utf-8 /MP -DHAVE_STDINT_H /Ox /GL -DNDEBUG  /Zl /MT /D_CRT_SECURE_NO_DEPRECATE /D_CRT_NONSTDC_NO_DEPRECATE -DFEAT_MBYTE_IME -DDYNAMIC_IME -DFEAT_GUI_MSWIN -DFEAT_DIRECTX -DDYNAMIC_DIRECTX -DFEAT_DIRECTX_COLOR_EMOJI -DDYNAMIC_ICONV -DDYNAMIC_GETTEXT -DFEAT_LUA -DDYNAMIC_LUA  -DDYNAMIC_LUA_DLL=\"lua53.dll\" -DFEAT_PYTHON3 -DDYNAMIC_PYTHON3 -DDYNAMIC_PYTHON3_DLL=\"python39.dll\" -DFEAT_HUGE /Fd.\ObjGXUHKAMD64/ /Zi
リンク: link  /nologo /opt:ref /LTCG:STATUS /HIGHENTROPYVA:NO oldnames.lib kernel32.lib advapi32.lib shell32.lib gdi32.lib  comdlg32.lib ole32.lib netapi32.lib uuid.lib /machine:AMD64 gdi32.lib version.lib  Dwmapi.lib  winspool.lib comctl32.lib advapi32.lib shell32.lib netapi32.lib  /machine:AMD64  libcmt.lib  user32.lib  /nodefaultlib:lua53.lib    /nodefaultlib:python39.lib    winmm.lib WSock32.lib Ws2_32.lib xpm\x64\lib-vc14\libXpm.lib  /PDB:gvim.pdb -debug

• :checkhealth or :CheckHealth result(neovim only):

Provide a minimal init.vim/vimrc with less than 50 lines (Required!)

Save the following file as a repro.vim.

set nocompatible laststatus=2 cmdheight=2

" Please prepare dependencies in the current directory or specify the path to
" those plugins.
" - 'vim-denops/denops.vim'
" - 'Shougo/ddc.vim'
" - 'Shougo/ddc-matcher_head'
" - 'Shougo/ddc-sorter_rank'
" - 'Shougo/neco-vim'
set runtimepath+=denops.vim,ddc.vim,ddc-matcher_head,ddc-sorter_rank,neco-vim

" Register a lot of functions.
for i in range(20000)
  function! ASDF{i}() abort
  endfunction
endfor

call ddc#custom#patch_global('sourceOptions', {
  \   '_': {
  \     'matchers': ['matcher_head'],
  \     'sorters': ['sorter_rank'],
  \   },
  \ })
call ddc#custom#patch_filetype(['vim'], 'sources', ['necovim'])

" This manual completion is not required
inoremap <silent><expr> <C-Space> ddc#manual_complete()

call ddc#enable()

How to reproduce the problem from neovim/Vim startup (Required!)

0. Prepare dependencies
1. gvim -u repro.vim test.vim
2. :set ft=vim
3. Type call exp in insert mode and wait for compleion (or press to force completion).
4. You'll see error message as below and no completions show up.

5. :message to see complete error messages.

Screenshot (if possible)

Very long error messages show up like below.

[Shougo]

It seems denops error. It is hard to debug for me.

[Shougo]

It is reproduced in Windows environment. Not reproduced in Linux.

[Shougo]

I have analysed the error. It is from channel JSON RPC.
It cannot be fixed in denops side.

I have added the filter for neco-vim.
Please update neco-vim to the latest.