bug#20580: 25.0.50; python-shell-completion-complete-or-indent hangs emacs with ipython v 3.1.0

[Andreas Tjärnberg]

Hi,

Short description:
When activating python with the ipython shell interpreter version 3.1.0
(latest) inside a virtual environment, TAB completion both in the
(run-python) shell and in a python file buffer hangs emacs.
I have to C-g to get back to the cursor.

Long description:
I use el-get to fetch the pyvenv package.
recipe to duplicate starting with:

$ emacs -q -l setup.el

8< cut here -------- setup.el -------- begin

(setq emacs-init-dir
      (file-name-directory (or load-file-name (buffer-file-name))))

(setq el-get-dir (expand-file-name "el-get" emacs-init-dir))
(add-to-list 'load-path (concat emacs-init-dir "el-get/el-get"))

(unless (require 'el-get nil 'noerror)
  (with-current-buffer
      (url-retrieve-synchronously
       "https://raw.github.com/dimitri/el-get/master/el-get-install.el";)
    (let (el-get-master-branch)
      (goto-char (point-max))
      (eval-print-last-sexp))))

(add-to-list 'el-get-recipe-path (concat emacs-init-dir "recipes"))

(el-get 'sync '(pyvenv))

(setq
   python-shell-interpreter "ipython"
   python-shell-interpreter-args "--no-confirm-exit --no-banner"
   python-shell-prompt-regexp "In \\[[0-9]+\\]: "
   python-shell-prompt-output-regexp "Out\\[[0-9]+\\]: ")

8< cut here -------------------------- end

now I proceed to create a virtual environment for python in the terminal
$ mkvirtualenv ipython_hangs_emacs

and install ipython with:
$ pip install ipython

Inside emacs I now use pyvenv-workon to work in this virtual environment.
and do
M-x run-python

Here is where the trouble start. The command hangs emacs but still
launches a *Python* shell buffer. C-g will give back control to me.

Now switching to the *Python* buffer and pressing TAB will hang emacs
until I C-g.

Running the code from the command
(message python-shell-completion-setup-code)
directly in the python shell
will complete without error, and I can call the function
';'.join(__PYTHON_EL_get_completions('''%s'''))
from the variable (python-shell-completion-module-string-code),
typed in to the python buffer with %s changed to something like "from sy"
will return a string with completions.

If I just run the above with the ipython version got from apt-get in Ubuntu,
everything works as expected but switching to an environment and
pip installing ipython doesn't.

The TAB key is mapped to (python-shell-completion-complete-or-indent)
but the code for completion seems to work,
however the help "C-h f" buffer does not suggest a file of origin for
this function so I
couldn't go further and doubt it would have helped any way becouse my
elisp knowledge only stretch so far.
But I assume, based on this, that the issue is there somewhere. 

Thank you for your help.

Regards
Andreas
-------------------------------------------------------------------------

In GNU Emacs 25.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.10.8)
 of 2015-05-08 on lgw01-14
Windowing system distributor `The X.Org Foundation', version 11.0.11501000
System Description:     Ubuntu 14.04.2 LTS

Configured using:
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