Re: [gentoo-dev] Things one could be upset about

[Andrew Savchenko]

On Tue, 20 Jan 2015 07:46:32 +0100 Róbert Čerňanský wrote:
> On Tue, 20 Jan 2015 00:14:29 +0300
> Andrew Savchenko <bircoph@g.o> wrote:
>
> > On Mon, 19 Jan 2015 21:44:25 +0100 Róbert Čerňanský wrote:
> > > From my point of view it would do much help if portage resolves USE
> > > dependencies automatically instead of telling the user to change USE
> > > flags manually (I am talking about bug #258371).
> >
> > As the user the last thing I want is to have some USE flags changed
> > without my permission ending up stuff I need to be omitted or stuff
> > I don't want to see on my system to be installed. Of course if
> > someone prefers USE flags to be randomly changed I don't mind if
> > such option will exist (as proposed in bug #258371) as long as it
> > is disabled by default.
>
> Is is of course perfectly fine to have that option disabled by
> default.  But I am afraid that I do not quite understand yours and
> Daniel's concerns.  If I paraphrase your statement with regards to
> current dependency handling, it is as if you were saying: "I do not
> want portage to install any package automatically by its own, I want
> to install all the dependencies explicitly."

The paraphrasing above is wrong. What I want to say is "I don't want
portage to automagically change _functionality_ of my packages on
its own, even in order to solve dependencies."
 
> Why we allow portage to install dependencies and still have things
> under control?  Well we have --pretend and --ask options and we can
> see what would/will be done.  This would be the same with USE flags.
> You would see in the --pretend output which flags would be changed.

No this wouldn't be the same. USE flags are _not_ equal to package
dependencies, sometimes they will not trigger dependency change at
all. USE flags are about _functionality_, dependencies are about
the _means_ to implement that functionality (as well as base
functionality of a package).

> To match the package dependency handling, there should be also an
> option equivalent to --depclean.  It would revert the USE changes
> which were done because of dependencies requirements if no longer
> needed.

This will dramatically increase complexity of dependencies metadata
as well as of algorithms to handle it (and they are already slow),
with no clear benefits therefore. No, thanks.

> For example, lets have following packages:
>
> - libbar
> - libfoo with IUSE=bar, which depends on: bar? ( libbar )
> - foo, which depends on: libfoo[bar]
>
> USE flag bar is not enabled.  You want to install application foo.
>
> Current behaviour:
>
> # emerge -av foo
> ...
> Required USE changes:
> libfoo +bar
> ... (sorry for not exact emerge output but you get the idea)
>
> Now, you either fire up your favorite editor and add "libfoo +bar" to
> /etc/portage/package.use, re-run emerge and have libbar installed even
> you do not want it.  The other option is not to install application
> foo at all.
>
> If you choose to emerge it and after year or so you decide to unmerge
> it because you do not need it anymore you still will have a leftover
> in package.use file - the line "libfoo +foo" even if you run emerge
> --depclean.
>
> New behaviour with automatic USE dependencies resolution:
>
> emerge -av foo
> [ebuild  N     ] libbar
> [ebuild  N     ] libfoo +bar
> [ebuild  N     ] foo
>
> Now, you can hit Y if you agree what portage wants to do or N and not
> to install foo at all.

And if I don't agree? What if for some reason I don't want to
have libfoo[bar] on my system. What If preferred solution will
be not to use libbar at all and to use libclue instread? 

World update on my systems usually involves about 2000 of packages.
It's already hard to read emerge -DNuav output in order to check
for new packages, dependencies, downgraded and removed packages.
Automagick dependency change will make this even harder, much
harder because it will involve multiple additional emerge runs in
order to deal with issues properly. And each run takes about half
an hour.

Yet again, Gentoo is all about choise. If someone wants that
automagick to be implemented, go ahead and send patches for
developers to review. But please keep it disabled by default, in
most cases it will provide bizarre results anyway. (Think about
conflicting alternatives, no sane way to prefer one above another
automatically and a chain of such issues during world update.) 

Best regards,
Andrew Savchenko