Re: [gentoo-dev] Underscores in USE flags

[Mike Gilbert <floppym@gentoo.org>]

On Fri, Sep 20, 2019 at 3:03 PM Haelwenn (lanodan) Monnier
<contact@hacktivis.me> wrote:
>
> [2019-09-20 13:24:45-0400] Mike Gilbert:
> > On Fri, Sep 20, 2019 at 12:55 PM Michał Górny <mgorny@gentoo.org> wrote:
> > > On Fri, 2019-09-20 at 12:41 -0400, Mike Gilbert wrote:
> > > > On Fri, Sep 20, 2019 at 12:11 PM Michał Górny <mgorny@gentoo.org> wrote:
> > > > > On Fri, 2019-09-20 at 11:46 -0400, Mike Gilbert wrote:
> > > > > > Recently, a large number of bugs were filed against packages that have
> > > > > > USE flag names which contain underscores. Apparently PMS prohibits
> > > > > > this except when the USE flag is part of a USE_EXPAND variable.
> > > > > >
> > > > > > https://projects.gentoo.org/pms/7/pms.html#x1-200003.1.4
> > > > > >
> > > > > > I'm not certain when this text was added to PMS, or how many of the
> > > > > > affected USE flags pre-date this policy.
> > > > > >
> > > > > > Portage seems to have no issue dealing with underscores, so this
> > > > > > doesn't seem to be solving any technical problem.
> > > > > >
> > > > > > I am pretty sure that renaming a bunch of USE flags will cause some
> > > > > > amount of end-user confusion, for very little benefit. Is enforcing
> > > > > > this part of PMS really worth it?
> > > > >
> > > > > And having packages with pretended-USE_EXPAND-that-does-not-work-as-
> > > > > USE_EXPAND is less confusing to the users?
> > > >
> > > > I doubt users immediately think "USE_EXPAND" when they see an underscore.
> > > >
> > > > Portage's seems fairly unambiguous to me. For example:
> > > >
> > > > % emerge -pv1O app-misc/foo
> > > >
> > > > These are the packages that would be merged, in order:
> > > >
> > > > [ebuild  N     ] app-misc/foo-0::local  USE="-modern_kernel"
> > > > PYTHON_TARGETS="python3_7" VIDEO_CARDS="radeon" 0 KiB
> > > >
> > > > Total: 1 package (1 new), Size of downloads: 0 KiB
> > > >
> > > > I don't think anyone would mistake "modern_kernel" for a USE_EXPAND
> > > > value  given the above.
> > >
> > > Look at the humongous list of flags on dev-libs/aws-sdk-cpp.  They all
> > > start with 'aws_targets' which is a clear attempt to emulate USE_EXPAND.
> > > Expect that they won't work as USE_EXPAND, user typing:
> > >
> > >   AWS_TARGETS="foo bar baz"
> > >
> > > will just wildly confused, and in the end this prefixing is just silly
> > > and causes the flag names to become awfully long.
> >
> > Ok, so you chery-picked one particularly horrible example. The Portage
> > output still puts them in USE="" section, though the user probably
> > won't see that given the massive USE flag list.
> >
> > My point still stands for many of the other packages in the repo that
> > don't have several dozen flags.
>
> While that's true for portage, it is false for gentoolkit with the
> `equery u <atom>` command.
>
> Following your original example it would be something like:
>
> % equery y app-misc/foo
> [ Legend : U - final flag setting for installation]
> [        : I - package is installed with flag     ]
> [ Colors : set, unset                             ]
>  * Found these USE flags for app-misc/foo-0::local
>  U I
>  - - modern_kernel            : Install init scripts for 3.18 or higher kernels with atomic rule updates
>  + + python_targets_python3_7 : Build with Python 3.7
>  - - video_cards_radeon       : VIDEO_CARDS setting to build driver for ATI radeon video cards
>
> And with a bunch more of USE flags (not with having to go to extremes like
> dev-libs/aws-sdk-cpp) it is very confusing a lot of time on machines where
> app-portage/eix would be overkill I had to check on another machine.

Ah, thank you for the example. I imagine equery is used quite
frequently for this sort of thing, so I'll concede the point.

It would be nice if there were some easy way to migrate package.use
settings; that's going to cause some grumbling from sysadmins.