[NVIM] YCM autoinstall, fix python path

nvim/init.vim

@@ -1,10 +1,11 @@
 set nocompatible
 filetype off
 
+
 " Plugins
 " Note: on most systems, this will make the plugins reside in \
 " ~/.local/share/nvim/plugged/
-let data_dir = has('nvim') ? stdpath('data') . '/site' : '~/.vim'
+let data_dir = has('nvim') ? stdpath('data') . '/site' : expand('~/.vim')
 if empty(glob(data_dir . '/autoload/plug.vim'))
   silent execute '!curl -fLo '.data_dir.'/autoload/plug.vim --create-dirs  https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim'
   let &runtimepath = &runtimepath
@@ -14,6 +15,19 @@ endif
 " Disable Perl
 let g:loaded_perl_provider = 0
 
+" Find python
+if has("macunix")
+    " Required for virtualenvs
+    let arch=substitute(system('uname -m'), '\n', '', '')
+    if arch == 'arm64'
+        let g:python_interpreter=expand("~/python-envs/neovim/bin/python3")
+    else
+        let g:python_interpreter="/usr/local/bin/python3"
+    endif
+else
+    let g:python_interpreter = 'python3'
+endif
+
 call plug#begin()
 
 " Warn about plugin updates
@@ -44,7 +58,17 @@ Plug 'ConradIrwin/vim-bracketed-paste'
 Plug 'christoomey/vim-tmux-navigator'
 
 " YouCompleteMe
-Plug 'Valloric/YouCompleteMe'
+function! BuildYCM(info)
+  " info is a dictionary with 3 fields
+  " - name:   name of the plugin
+  " - status: 'installed', 'updated', or 'unchanged'
+  " - force:  set on PlugInstall! or PlugUpdate!
+  if a:info.status == 'installed' || a:info.force
+    execute '!' . g:python_interpreter . ' ./install.py --all'
+  endif
+endfunction
+
+Plug 'ycm-core/YouCompleteMe', { 'do': function('BuildYCM') }
 Plug 'rdnetto/YCM-Generator'
 
 " Git
@@ -218,9 +242,11 @@ nmap <C-]> <C-w><C-]><C-w>T
 
 " YouCompleteMe
 let g:ycm_collect_identifiers_from_tags_files = 1 " Read from tag files
-let g:ycm_global_ycm_extra_conf = '~/.config/nvim/.ycm_extra_conf.py' " Standard conf
+let g:ycm_global_ycm_extra_conf = expand('~/.config/nvim/.ycm_extra_conf.py') " Standard conf
 let g:ycm_enable_diagnostic_signs = 0 " Do not show semantic error bar
-let g:ycm_server_python_interpreter = 'python3'
+let g:ycm_server_python_interpreter=g:python_interpreter
+" Enable virtualenv autocompletion
+let g:ycm_python_binary_path = 'python'
 let g:ycm_key_list_select_completion   = ['<C-j>', '<C-n>', '<Down>']
 let g:ycm_key_list_previous_completion = ['<C-k>', '<C-p>', '<Up>']
 
@@ -284,13 +310,4 @@ catch
 endtry
 let g:tex_flavor = "latex"
 autocmd FileType yaml setlocal ts=2 sts=2 sw=2 expandtab
-
-if has("macunix")
-    " Required for virtualenvs
-    let arch=substitute(system('uname -m'), '\n', '', '')
-    if arch == 'arm64'
-        let g:python3_host_prog="~/python-envs/neovim/bin/python3"
-    else
-        let g:python3_host_prog="/usr/local/bin/python3"
-    endif
-endif
+let g:python3_host_prog=g:python_interpreter