python-try-complete

[Julian Scheid <julians37@googlemail.com>]

Hi,

first of all I am writing a lot of Python code these days and 
python-mode is indispensable.  Thanks for this great tool.

I take issue with one of its design decisions however: sneaking in 
python-try-complete into hippie-expand-try-functions-list.  From 
python.el (found in both my 22.1.2 and in HEAD):

   (if (featurep 'hippie-exp)
       (set (make-local-variable 'hippie-expand-try-functions-list)
	   (cons 'python-try-complete hippie-expand-try-functions-list)))

The main reason why I use hippie-expand (and similar completion 
facilities in Emacs) is simply raw speed.  I'll take lightweight, 
context-insensitive completion over heavyweight, database-querying or 
external-process-launching context-sensitive completion any day.

I am defining hippie-expand-try-functions-list explicitly in my .emacs 
and until recently I was under the impression that this way I get to 
choose which route hippie-expand takes to try and complete.  But the 
other day I learned that python-try-complete gets inserted into that 
list without my consent, a function that launches an external process 
and which I would thus consider quite heavyweight.

I understand that this has been done with only the best intentions but I 
would like to kindly ask the maintainers of python-mode to remove this 
and instead advertise the existence of python-try-complete and leave it 
up to hippie-expand users to insert or not insert it into their list of 
functions to try.

Alternatively, there could be a customization setting for this which 
defaults to off (no automatic registration of python-try-complete).  I 
think that the lo-fi approach of having people add it to their list 
explicitly would be superior, though, because this way users get more 
control over the order in which the functions are invoked.

FWIW my current unsophisticated workaround looks like this:

   (require 'python)
   (defun python-try-complete (old) nil)


The second problem I noticed with python-try-complete, and this is what 
made me aware of it being used in the first place, is that it will 
apparently launch the Python interpreter on a remote host if the file in 
question is remote, opened using Tramp in my case. This remote 
invocation often (always?) fails, apparently due to shell quoting issues.

That wouldn't be a big problem if the completion attempt would simply be 
ignored in case of failure; however it seems as if python-try-complete 
would get stuck this way (I think it's waiting indefinitely for a reply 
from the remote Python script), forcing me to C-g out of it which is 
quite a nuisance in interactive usage when all you wanted is get an 
expansion of the word at point.

I got the following information from Michael, the tramp maintainer, 
about this situation - and I'm not quoting directly here, any errors in 
the following are mine and not his:

Either python-try-complete should refrain from launching the process 
remotely by looking at (file-remote-p default-directory), or the scripts 
it launches need to be prepared (e.g. in terms of quoting) for being run 
remotely via ssh.

If you need backtraces or similar for tracking this down I'm happy to 
provide them the next time I'm in a situation to reproduce the issue.

Let me know in case my explanation of these problems was insufficient.

I'm using Emacs 22.1.2, hippie-expand 1.6, tramp 2.1.13, and python.el 
that ships with my Emacs.

-Julian