Vim omnicomplete with Ruby 2.3.1

Question

I've recently learned about Vim's omnicompletion and while attempting to make it work, I get the error Pattern not found. To test it I used the following code:

class C
  def hello
    puts "Hello, World!"
  end
  def goodbye
    puts "Goodbye, cruel world!"
  end
end

x = C.new

x.<C-x><C-o>

Which gives the error Pattern not found.

My version of Vim is compiled with +ruby/dyn, and it seems that the error is because the file Vim is trying to load doesn't match my version of Ruby, which seemed to be a problem for some other people using Ruby 1.9.x in another forum thread I saw. In :h ruby-dynamic that you are able to change the library it uses with 'rubydll', but it must be the same version that Vim is compiled with. My version of Vim is 8.0.5 and I'm using Ruby 2.3.1. I also read in :h 'rubydll' that the default library to use is DYNAMIC_RUBY_DLL which is set at compile time, but I'm not sure how to check what this is set to.

UPDATE: vim --version output:

VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Sep 15 2016 10:09:09)
Included patches: 1-5
Compiled by Arch Linux
Huge version with GTK2 GUI.  Features included (+) or not (-):
+acl             +file_in_path    +mouse_sgr       +tag_old_static
+arabic          +find_in_path    -mouse_sysmouse  -tag_any_white
+autocmd         +float           +mouse_urxvt     +tcl/dyn
+balloon_eval    +folding         +mouse_xterm     +termguicolors
+browse          -footer          +multi_byte      +terminfo
++builtin_terms  +fork()          +multi_lang      +termresponse
+byte_offset     +gettext         -mzscheme        +textobjects
+channel         -hangul_input    +netbeans_intg   +timers
+cindent         +iconv           +num64           +title
+clientserver    +insert_expand   +packages        +toolbar
+clipboard       +job             +path_extra      +user_commands
+cmdline_compl   +jumplist        +perl/dyn        +vertsplit
+cmdline_hist    +keymap          +persistent_undo +virtualedit
+cmdline_info    +lambda          +postscript      +visual
+comments        +langmap         +printer         +visualextra
+conceal         +libcall         +profile         +viminfo
+cryptv          +linebreak       +python/dyn      +vreplace
+cscope          +lispindent      +python3/dyn     +wildignore
+cursorbind      +listcmds        +quickfix        +wildmenu
+cursorshape     +localmap        +reltime         +windows
+dialog_con_gui  +lua/dyn         +rightleft       +writebackup
+diff            +menu            +ruby/dyn        +X11
+digraphs        +mksession       +scrollbind      -xfontset
+dnd             +modify_fname    +signs           +xim
-ebcdic          +mouse           +smartindent     -xpm
+emacs_tags      +mouseshape      +startuptime     +xsmp_interact
+eval            +mouse_dec       +statusline      +xterm_clipboard
+ex_extra        +mouse_gpm       -sun_workshop    -xterm_save
+extra_search    -mouse_jsbterm   +syntax          
+farsi           +mouse_netterm   +tag_binary      
   system vimrc file: "/etc/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "/etc/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: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK  -pthread -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/libdrm -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng16 -I/usr/include/pango-1.0 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -D_FORTIFY_SOURCE=2  -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1      
Linking: gcc   -L. -Wl,-O1,--sort-common,--as-needed,-z,relro -fstack-protector -rdynamic -Wl,-export-dynamic -Wl,-E -Wl,-rpath,/usr/lib/perl5/core_perl/CORE  -Wl,-O1,--sort-common,--as-needed,-z,relro -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 -lXt -lX11 -lXdmcp -lSM -lICE  -lm -lncurses -lelf -lnsl    -lacl -lattr -lgpm -ldl   -Wl,-E -Wl,-rpath,/usr/lib/perl5/core_perl/CORE -Wl,-O1,--sort-common,--as-needed,-z,relro -fstack-protector-strong -L/usr/local/lib  -L/usr/lib/perl5/core_perl/CORE -lperl -lpthread -lnsl -ldl -lm -lcrypt -lutil -lc   -L/usr/lib -ltclstub8.6 -ldl -lz -lpthread -lieee -lm  

Answer 1

Just solved my problem. Not 100% sure how, but I'll do my best to explain all the steps I took:

1. Installed Vundle and configured it to manage vim-ruby and neocomplete, ran :PluginInstall and :PluginUpdate a few times, tried rebooting

2. Added the following lines to my .vimrc, found in another thread:

   autocmd FileType ruby,eruby let g:rubycomplete_buffer_loading = 1
   autocmd FileType ruby,eruby let g:rubycomplete_classes_in_global = 1
   autocmd FileType ruby,eruby let g:rubycomplete_rails = 1
   

It still wasn't working at this point, but after I ran :PluginUpdate again, it seemed to work. It seems like those three lines were what fixed it. Thanks for your help.

Answer 2

Are you using any kind of auto-completion plugin, like neocomplete/YouCompleteMe? I also use Arch Linux and for me it gives completions. I use neocomplete and vim-ruby plugins, that probably add needed things to do the completion

EDIT: Relevant parts of my vimrc:

autocmd FileType ruby,eruby set omnifunc=rubycomplete#Complete
autocmd FileType ruby,eruby let g:rubycomplete_buffer_loading = 1 
autocmd FileType ruby,eruby let g:rubycomplete_classes_in_global = 1
autocmd FileType ruby,eruby let g:rubycomplete_rails = 1
autocmd FileType ruby compiler ruby

" Enable heavy omni completion.
if !exists('g:neocomplete#sources#omni#input_patterns')
    let g:neocomplete#sources#omni#input_patterns = {}
endif
if !exists('g:neocomplete#sources#omni#force_omni_input_patterns')
    let g:neocomplete#sources#omni#force_omni_input_patterns = {}
endif
let g:neocomplete#sources#omni#input_patterns.ruby = '[^.[:digit:] *\t]\%(\.\|->\)'