Hitting 'Enter' doesn't select item from the dropdown menu in Vim 8.1

[0xadb]

Issue Prelude

• [x ] I have read and understood YCM's CONTRIBUTING document.
• [x ] I have read and understood YCM's CODE_OF_CONDUCT document.
• [ x] I have read and understood YCM's README, especially the
  Frequently Asked Questions section.
• [ x] I have searched YCM's issue tracker to find issues similar to the one I'm
  about to report and couldn't find an answer to my problem. (Example Google
  search.)
• [x ] If filing a bug report, I have included the output of vim --version.
• [ x] If filing a bug report, I have included the output of :YcmDebugInfo.
• [ x] If filing a bug report, I have attached the contents of the logfiles using
  the :YcmToggleLogs command.
• [ x] If filing a bug report, I have included which OS (including specific OS
  version) I am using.
• [ x] If filing a bug report, I have included a minimal test case that reproduces
  my issue, including what I expected to happen and what actually happened.
• If filing a installation failure report, I have included the entire output
  of install.py (or cmake/make/ninja) including its invocation
• [ x] I understand this is an open-source project staffed by volunteers and
  that any help I receive is a selfless, heartfelt gift of their free time. I
  know I am not entitled to anything and will be polite and courteous.
• [ x] I understand my issue may be closed if it becomes obvious I didn't
  actually perform all of these steps.

Issue Details

• What did you do?

On Debian 9.4 I upgraded Vim from 8.0 (from repo) to 8.1 (from sources, following instructions from Full Installation Guide), i.e.:

• removed vim and vim-youcompleteme completely
• downloaded Clang precompiled binaries of clang-6.0 for Debian 8 x86_64
• built ycm_core.so using path to clang-6.0 root as -DPATH_TO_LLVM_ROOT=.
  C++ completion works fine, I see a dropdown menu with completion suggestions. But when I choose a suggestion using arrow keys and hit Enter key, the menu doesn't collapse as it's supposed to. Even after several Enters - menu collapses only after Esc.

1. Create main.cpp with this code:

struct Struct
{
  int intValue;
  char * strValue;
};
  
int main ()
{
  Struct s;
  s // enter '.', select an item and hit 'Enter'
  return 0;
}

2. After 's' enter '.', select a suggestion from dropdown menu and hit 'Enter'

• What did you expect to happen?

On vim 8.0 selecting menu item and pressing Enter led to menu collapsing. It was convenient.

• What actually happened?

Before hitting Enter:

After hitting Enter

Diagnostic data

Output of vim --version

VIM - Vi IMproved 8.1 (2018 May 17, compiled May 19 2018 11:58:46)
Included patches: 1
Compiled by user@box
Huge version with GTK2 GUI. Features included (+) or not (-):
+acl +farsi +mouse_sgr -tag_any_white
+arabic +file_in_path -mouse_sysmouse -tcl
+autocmd +find_in_path +mouse_urxvt +termguicolors
-autoservername +float +mouse_xterm +terminal
+balloon_eval +folding +multi_byte +terminfo
+balloon_eval_term -footer +multi_lang +termresponse
+browse +fork() -mzscheme +textobjects
++builtin_terms +gettext +netbeans_intg +timers
+byte_offset -hangul_input +num64 +title
+channel +iconv +packages +toolbar
+cindent +insert_expand +path_extra +user_commands
+clientserver +job +perl +vertsplit
+clipboard +jumplist +persistent_undo +virtualedit
+cmdline_compl +keymap +postscript +visual
+cmdline_hist +lambda +printer +visualextra
+cmdline_info +langmap +profile +viminfo
+comments +libcall -python +vreplace
+conceal +linebreak +python3 +wildignore
+cryptv +lispindent +quickfix +wildmenu
+cscope +listcmds +reltime +windows
+cursorbind +localmap +rightleft +writebackup
+cursorshape +lua +ruby +X11
+dialog_con_gui +menu +scrollbind -xfontset
+diff +mksession +signs +xim
+digraphs +modify_fname +smartindent +xpm
+dnd +mouse +startuptime +xsmp_interact
-ebcdic +mouseshape +statusline +xterm_clipboard
+emacs_tags +mouse_dec -sun_workshop -xterm_save
+eval -mouse_gpm +syntax
+ex_extra -mouse_jsbterm +tag_binary
+extra_search +mouse_netterm +tag_old_static
system vimrc file: "$VIM/vimrc"
user vimrc file: "$HOME/.vimrc"
2nd user vimrc file: "/.vim/vimrc"
user exrc file: "$HOME/.exrc"
system gvimrc file: "$VIM/gvimrc"
user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "/.vim/gvimrc"
defaults file: "$VIMRUNTIME/defaults.vim"
system menu file: "$VIMRUNTIME/menu.vim"
fall-back for $VIM: "/opt/vim-8.1/share/vim"
f-b for $VIMRUNTIME: "/opt/vim-8.1/share/vim/vim81"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK -pthread -I/usr/include/gtk-2.0 -I/usr/lib/x86_64-linux-gnu/gtk-2.0/include -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/libpng16 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng16 -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/freetype2 -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic -Wl,-E -L/usr/local/lib -Wl,--as-needed -o vim -lgtk-x11-2.0 -lgdk-x11-2.0 -lpangocairo-1.0 -latk-1.0 -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lpangoft2-1.0 -lpango-1.0 -lgobject-2.0 -lglib-2.0 -lfontconfig -lfreetype -lSM -lICE -lXpm -lXt -lX11 -lXdmcp -lSM -lICE -lm -ltinfo -lnsl -lselinux -ldl -L/usr/lib -llua5.1 -Wl,-E -fstack-protector-strong -L/usr/local/lib -L/usr/lib/x86_64-linux-gnu/perl/5.24/CORE -lperl -ldl -lm -lpthread -lcrypt -L/usr/lib/python3.5/config-3.5m-x86_64-linux-gnu -lpython3.5m -lpthread -ldl -lutil -lm -lruby-2.3 -lpthread -lgmp -ldl -lcrypt -lm

Output of YcmDebugInfo

Printing YouCompleteMe debug information...
-- Client logfile: /tmp/ycm_c0qz25yi.log
-- Server Python interpreter: /usr/bin/python3.5
-- Server Python version: 3.5.3
-- Server has Clang support compiled in: True
-- Clang version: clang version 6.0.0 (tags/RELEASE_600/final)
-- Extra configuration file found and loaded
-- Extra configuration path: /home/user/.ycm_extra_conf.py
-- C-family completer debug information:
-- Compilation database path: None
-- Flags: ['-Wall', '-Wextra', '-Werror', '-Wc++98-compat', '-Wno-long-long', '-Wno-va
riadic-macros', '-fexceptions', '-DNDEBUG', '-DUSE_CLANG_COMPLETER', '-std=c++11', '-x',
'c++', '-isystem', '/home/user/../BoostParts', '-isystem', '/System/Library/Framew
orks/Python.framework/Headers', '-isystem', '/home/user/../llvm/include', '-isystem
', '/home/user/../llvm/tools/clang/include', '-I', '/home/user/.', '-I', '/hom
e/user/./ClangCompleter', '-isystem', '/home/user/./tests/gmock/gtest', '-isys
tem', '/home/user/./tests/gmock/gtest/include', '-isystem', '/home/user/./test
s/gmock', '-isystem', '/home/user/./tests/gmock/include', '-resource-dir=/home/bere
govoy/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/../clang_includes', '-fspell-check
ing']
-- Translation unit: /home/user/playground/ycm_test/main.cpp
-- Server running at: http://127.0.0.1:58487
-- Server process ID: 21461
-- Server logfiles:
-- /tmp/ycmd_58487_stdout_vlihtjga.log
-- /tmp/ycmd_58487_stderr_jwq1mtmn.log

Contents of YCM, ycmd and completion engine logfiles

ycm_c0qz25yi.log
ycmd_58487_stderr_jwq1mtmn.log
ycmd_58487_stdout_vlihtjga.log

OS version, distribution, etc.

$ uname -a
Linux box 4.9.0-6-amd64 #1 SMP Debian 4.9.88-1+deb9u1 (2018-05-07) x86_64 GNU/Linux

$ cat /etc/debian_version
9.4

[micbou]

I can't reproduce the issue. Did you remap the <Enter> key? Does the command

:inoremap <Enter>

return anything? By default, the <Enter> key should always insert a new line even in completion mode. If you want this key to confirm the selection instead of inserting a new line, you should add it to the g:ycm_key_list_stop_completion option:

let g:ycm_key_list_stop_completion = [ '<C-y>', '<Enter>' ]

[micbou]

By the way, you should be able to install YCM with the install.py script instead of following the full instructions on Debian. The command

./install.py --clang-completer

should work. Don't worry if it's downloading the Clang binaries for Ubuntu 14.04. They are compatible with Debian.

[0xadb]

:inoremap <Enter>

i * pumvisible() ? "<C-Y>" : "<C-G>u<CR>"

I am a moron, totally forgot about OmniCompletion enabled:

"" Enable OmniCompletion
" http://vim.wikia.com/wiki/Omni_completion
filetype plugin on
set omnifunc=syntaxcomplete#Complete
" "
" " " Configure menu behavior
" " " http://vim.wikia.com/wiki/VimTip1386
set completeopt=longest,menuone
inoremap <expr> <CR> pumvisible() ? "\<C-y>" : "\<C-g>u\<CR>"
inoremap <expr> <C-n> pumvisible() ? '<C-n>' :
  \ '<C-n><C-r>=pumvisible() ? "\<lt>Down>" : ""<CR>'
inoremap <expr> <M-,> pumvisible() ? '<C-n>' :
  \ '<C-x><C-o><C-n><C-p><C-r>=pumvisible() ? "\<lt>Down>" : ""<CR>'

I'm sorry and thank you.

Works now as I expect it to.