[Distutils] Request for comment: Proposal to change behaviour of pip install

[Paul Moore]

On 25 June 2016 at 23:40, Nathaniel Smith <njs at pobox.com> wrote:
> Of course, there is a third mental state that the user might have been
> in: that they didn't know whether 'foo' is installed, and they wanted
> to guarantee that some version of 'foo' is installed, but they
> genuinely didn't care what version that is, *and* they'd prefer to
> keep an old version rather than upgrade. That's a fairly odd and
> complicated mental state to be in, but I guess it does come up
> sometimes (like in Ian's use case of writing automated sysadmin
> scripts).

It's not *that* strange a mental state. Windows users often have
issues installing packages, either because they don't have a compiler,
or because dependencies are hard to get right. So "don't do any
non-essential install steps in case they go wrong" is an entirely
reasonable viewpoint. And then, "pip install foo" meaning "install a
copy if it's not there, otherwise leave me with my working version"
seems to me to be a perfectly sensible expectation.

Actually, that's more general than just windows. Wanting to have foo
available, but not wanting to risk the possibility of a failed install
for *whatever* reason, seems reasonable. Maybe it's just that Windows
users are more used to installs failing (before wheels became common)?

Paul