Error when adding ensime-vim to vim73 on ubuntu lts 12.04

[jwatte]

2. step by step instructions to trigger the bug

A. Install vundle on vim73 on ubuntu 12.04 LTS
B. Install ensime-vim as per steps in the instructions
C. Run :PluginInstall and wait for it to complete
D. Quit vim, and re-start vim
E. See this error in vim:

$ vim
Error detected while processing function <SNR>14_DependenciesValid:
line   12:
Traceback (most recent call last):
  File "<string>", line 6, in <module>
AttributeError: 'module' object has no attribute 'vars'
Press ENTER or type command to continue

3. commit your .ensime into the repository (or in a gist)

I don't get that far. This is a problem with ensime-vim, causing an error on start-up of vim.

Here is my .vimrc:

$ cat ~/.vimrc
set nocompatible
filetype off

" set the runtime path to include Vundle and initialize
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()

" let Vundle manage Vundle, required
Plugin 'VundleVim/Vundle.vim'

Plugin 'jewes/Conque-Shell'
Plugin 'ensime/ensime-vim'
Plugin 'derekwyatt/vim-scala'

" All of your Plugins must be added before the following line
call vundle#end()            " required
filetype plugin indent on    " required

" My Stuff
set expandtab
set hidden
set ts=4
set ignorecase
set sw=4

Disabling ensime/ensime-vim makes the error not print.
Disabling Conque-Shell or vim-scala does not make the error not print.

HEAD of .vim/bundle/ensime-vim is this:

commit 1b32e85f5c1883af3946cf2bf7a39f60801f47b1
Author: Ches Martin <ches@whiskeyandgrits.net>
Date:   Sat Jan 7 00:54:32 2017 +0700

Fail fast if our python dependencies aren't installed (#368)

The python requirements are installed; I ran as indiceted in the docs: pip install websocket-client sexpdata

I think the problem is this; "vars" doesn't appear to be a member of the "vim" module:

" Fail fast if dependencies are missing, we can't do much useful if so.
" We need to wrap this in a function, see :help script-here
function! s:DependenciesValid() abort
    python <<PY
import vim
try:
    import sexpdata
    import websocket

    vim.vars['ensime_deps_valid'] = True
    del sexpdata # Clean up the shared interpreter namespace
    del websocket
except ImportError:
    vim.vars['ensime_deps_valid'] = False
    pass
PY

    return g:ensime_deps_valid
endfunction

Reverting this change (this is the latest commit on master) removes the error.

[ches]

Hi, yes you're right that vim.vars doesn't exist in Vim 7.3, we realized this on #368. I've opened a PR at #370 that works around this poor failure mode during Vim startup, but in truth there are other assumptions of Vim 7.4+ in our codebase so I'd really suggest that you upgrade Vim for use of this plugin.

Ubuntu 12.04 goes end-of-life in April so I'd consider it barely even a server-class OS release as of now—Vim 7.3 is becoming rare. I'd encourage people that really need to use ensime-vim in such an environment to find a PPA for newer Vim or Neovim packages, or add a conditional to your vimrc that avoids loading ensime-vim on these environments if you use your config on a mix of workstations and servers (we'll consider building in this check since there are other known incompatibilities already).

Thanks for the report and sorry about the ugly error behavior.