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

[Donald Stufft]

> On Jun 25, 2016, at 6:25 AM, Pradyun Gedam <pradyunsg at gmail.com> wrote:
> 
> There is currently a proposal to change the behaviour to pip install to upgrade a package that is passed even if it is already installed.
> 
> This behaviour change is accompanied with a change in the upgrade strategy - pip would stop “eagerly” upgrading dependencies and would become more conservative, upgrading a dependency only when it doesn’t meet lower constraints of the newer version of a parent. Moreover, the behaviour of pip install --target would also be changed so that --upgrade no longer affects it.
> 


I think bundling these two changes (and I think I might have been the one that originally suggested it) is making this discussion harder than it needs to be as folks are having to fight on multiple different fronts at once. I think the change to the default behavior of pip install is dependent on the change to —upgrade, so I suggest we focus on the change to —upgrade first, changing from a “recursive” to a “conservative” strategy. Once we get that change figured out and landed then we can worry about what to do with pip install.

I’m not going to repeat the entire post, but I just made a fairly lengthy comment at https://github.com/pypa/pip/issues/3786#issuecomment-228611906 <https://github.com/pypa/pip/issues/3786#issuecomment-228611906> but to try and boil it down to a few points:

* ``pip install —upgrade`` is not a good security mechanism, relying on it is inconsistent at best. If we want to support trying to keep people on secure versions of software we need a better mechanism than this anyways, so we shouldn’t let it influence our choice here.
* For the general case, it’s not going to matter a lot which way we go, but not upgrading has the greatest chance of not breaking *already installed software*.
* For the hard-to-upgrade case, the current behavior is so bad that people are outright attempting to subvert the way pip typically behaviors, *AND* advocating for other’s to do the same, in an attempt to escape that behavior. I think that this is not a good place to be in.

—
Donald Stufft



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