On Jul 14, 2013, at 10:39 AM, Noah Kantrowitz wrote: > > On Jul 14, 2013, at 10:31 AM, Ian Cordasco wrote: > >> On Sun, Jul 14, 2013 at 1:12 PM, Noah Kantrowitz <n...@coderanger.net> wrote: >>> >>> On Jul 14, 2013, at 9:45 AM, Steve Dower wrote: >>> >>>> From: Paul Moore >>>>> On 13 July 2013 10:05, Paul Moore <p.f.mo...@gmail.com> wrote: >>>>> How robust is the process of upgrading pip using itself? Specifically on >>>>> Windows, where these things typically seem less reliable. >>>>> >>>>> OK, I just did some tests. On Windows, "pip install -U pip" FAILS. The >>>>> reason >>>>> for the failure is simple enough to explain - the pip.exe wrapper is held >>>>> open >>>>> by the OS while it's in use, so that the upgrade cannot replace it. >>>>> >>>>> The result is a failed upgrade and a partially installed new version of >>>>> pip. In >>>>> practice, the exe stubs are probably added fairly late in the install (at >>>>> least >>>>> when installing from sdist, with a wheel that depends on the order of the >>>>> files >>>>> in the wheel), so it's probably only a little bit broken, but "a little >>>>> bit >>>>> broken" is still broken :-( >>>>> >>>>> On the other hand, "python -m pip install -U pip" works fine because it >>>>> avoids >>>>> the exe wrappers. >>>>> >>>>> There's a lot of scope for user confusion and frustration in all this. For >>>>> standalone pip I've tended to recommend "don't do that" - manually >>>>> uninstall and >>>>> reinstall pip, or recreate your virtualenv. It's not nice, but it's >>>>> effective. >>>>> That sort of advice isn't going to be realistic for a pip bundled with >>>>> CPython. >>>>> >>>>> Does anyone have any suggestions? >>>> >>>> Unless I misunderstand how the exe wrappers work (they're all the same >>>> code that looks for a .py file by the same name?) it may be easiest to >>>> somehow mark them as non-vital, such that failing to update them does not >>>> fail the installer. Maybe detect that it can't be overwritten, compare the >>>> contents/hash with the new one, and only fail if it's changed (with an >>>> instruction to use 'python -m...')? >>>> >>>> Spawning a separate process to do the install is probably no good, since >>>> you'd have to kill the original one which is going to break command line >>>> output. >>>> >>>> MoveFileEx (with its copy-on-reboot flag) is off the table, since it >>>> requires elevation and a reboot. But I think that's the only supported API >>>> for doing a deferred copy. >>>> >>>> If Windows was opening .exes with FILE_SHARE_DELETE then it would be >>>> possible to delete the exe and create a new one by the same name, but I >>>> doubt that will work and in any case could not be assumed to never change. >>>> >>>> So unless the exe wrapper is changing with each version, I think the best >>>> way of handling this is to not force them to be replaced when they have >>>> not changed. >>> >>> The usual way to do this is just move the existing executable to >>> pip.exe.deleteme or something, and then write out the new one. Then on >>> every startup (or maybe some level of special case for just pip upgrades?) >>> try to unlink *.deleteme. Not the simplest system ever, but it gets the job >>> done. >> >> I accidentally only emailed Paul earlier, but why can't we upgrade the >> pip module with the exe and then replace the process (using something >> in the os.exec* family) with `python -m pip update-exe` which could >> then succeed since the OS isn't holding onto the exe file? I could be >> missing something entirely obvious since I haven't developed >> (directly) on or for Windows in at least 5 years. > > Unfortunately windows doesn't actually offer the equivalent of a POSIX > exec(). The various functions in os don't actually replace the current > process, they just create a new one and terminate the old one. This means the > controlling terminal would see the pip process as ended, so it makes showing > output difficult at best.
Check that, maybe I'm wrong, does anyone know if the P_OVERLAY flag unlocks the original binary? /me drags out a windows VM … --Noah _______________________________________________ Distutils-SIG maillist - Distutils-SIG@python.org http://mail.python.org/mailman/listinfo/distutils-sig
