> On Jan 22, 2016, at 2:09 PM, Robert Collins <robe...@robertcollins.net> wrote: > > I think requiring a force flag to replace files installed by another > packaging tool is an unbreakme option as things stand, and so I'm very > concerned about the resulting user experience.
I don't think the current behavior makes *any* sense and represents nothing but a footgun where you end up with two systems fighting over what the content of a particular file is. Currently there are two sort of scenarios where something like this comes up: Debuntu ------- Current behavior is we'll uninstall the file sitting at /usr/lib/pythonX.Y/dist-packages/* and then we'll go ahead and install our own files into /usr/local/lib/pythonX.Y/dist-packages/*. Then, the next time that package gets an update the files are put back into place by dpkg into /usr/lib/pythonX.Y/dist-packages/* and we're finally at a consistent state where both package managers know the state of their respective systems. In the "you need a flag" future world, we would just skip uninstalling the files from /usr/lib/pythonX.Y/dist-packages/* and just install our own files into /usr/local/lib/pythonX.Y/dist-packages. Thus we never touch anything that isn't owned by us and Debian's internal systems stay consistent. If someone did only ``pip uninstall requests`` and that was located in the OS files, then we would refuse to uninstall it, directing them to the platform tooling instead. Everyone Else ------------- The /usr/lib and /usr/local/lib split is Debian specific (though at some point I want to bring it to upstream Python) so on other systems you have a single location, typically in /usr/lib/.../site-packages where both the OS and pip will be trying to modify files. Right now this is pure chaos, if python-requests is installed by the system, pip will come along and uninstall it then upgrade requests, then the next time an update is released, the system tooling will then come along and write all over the files that pip dropped into place, possibly corrupting things depending on how their patching works. Even for just ``pip uninstall foo``, it's really only uninstall until the next time that package gets updated. In the "you need a flag future", if python-requests is installed by the OS and it's in the same location that *we* want to write a file to, then we'll error out and require a --force flag. If it isn't already installed and nothing is in our way, then we'll go ahead and install to that location. This isn't as nice as the Debuntu world, but nothing will be without the patch that Debian has. Essentially though, ``pip install -U anything-installed-by-the-os`` is at best a no-op that deletes files for no good reason (Debuntu) or it's a field full of footguns where you're going to have two independent systems shitting all over each others files trying to do what they think the user wants. ----------------- Donald Stufft PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA
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