Use rlwrap if available for oracle backend dbshell

[Dan Davis]

PROBLEM

Oracle's SQL utility, sqlplus, is proprietary and closed source. On *NIX systems, it is not linked with GNU readline. So, using it in that environment is quite hard -- unless you use rlwrap. It is trivial to use rlwrap via an alias, but to get Django's manage.py dbshell to work properly requires changes to the backend.

DESIRED BEHAVIOR

The Oracle backend.client should look for rlwrap, and wrap sqlplus in rlwrap when rlwrap is available. If rlwrap is not available, then we will assume that's what there is.

[Dan Davis]

I think I can at least get as far as a pull request, but unit tests for Oracle may be tougher.

[Dan Davis]

Having worked on this briefly, I'm not really sure whether it is a good idea to support calling rlwrap if it is installed by hand - in that case, you can subclass the backend.

Both on CentOS 6, CentOS 7, and Ubuntu 16.04, the path to rlwrap is /usr/bin/rlwrap if it has been installed as a package.

So, the question is whether it is better to look for it in the path with shutil.which('rlwrap'), or whether it is better to only do this when it is "properly" installed in /usr/bin/rlwrap. I guess I should then check OS X, because there it may go elsewhere.

[Carlton Gibson]

Hi Dan.

This seems a reasonable addition. (At least pending the work on the PR! :-)

Thanks for the input!

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In c6525bea:

Fixed #29534 -- Made dbshell use rlwrap on Oracle if available.