Ühel kenal päeval, R, 03.06.2016 kell 22:40, kirjutas Daniel Campbell: > You touched on the part that I'm most concerned about: choosing. If > the > 'GUI' USE_EXPAND gets in, do we maintainers check that variable and > if > there's no preference just build whatever? Will we not be expected to > emit an ewarn or something similar to clarify *why* the package is > being > built a certain way? Granted, if a user has a problem and reports a > bug, > their make.conf's GUI variable should be present in emerge -v output, > easily explaining the issue.
Said 'GUI' USE_EXPAND is outside the intended scope of the USE=gui thread, but anticipating discussion will happen regardless now, I've cut the thread and named it something else. Many discussions have happened on IRC on this as well, which is where Daniel got this from. I think it's actually a rather corner-case to have an optional GUI, and then that GUI being buildable against a selection of toolkits. Arguably in some of those cases it might be more ideal to have the GUI parts in a separate package too, but usually upstream sources aren't so accommodating to our source-based case (while binary distributions split it up into multiple binary packages, built from one source in one go). In most cases when there's a choice, a GUI imho isn't usually optional. You choose e.g qt4 or qt5, or gtk3 or qt5 and having both shipped is not so common from the same package. Transmission is an example where it is, because they have a multiple frontend system (arguably it would be neat to have these in separate transmission-qt, transmission-gtk and so on packages), and one of these can be a web service UI instead of a dedicated graphics toolkit. USE=gui would replace a ton of USE=gtk's at least, where it's mostly about simple extra GUI tools added with a gtk2 dep, but I've seen it in other toolkit cases too, but I don't know how common it is there. Ideally USE=gui can be agreed upon while ignoring the corner-case of multiple choices; in some of these cases it might make sense to ignore USE=gui at the start, until the multiple choice case gets some resolution though, e.g emacs and perhaps transmission could just keep the current way until we agree how to express multiple choice cases universally. I drafted that mentioned USE_EXPAND idea as a means to get some 'design from the scratch' discussion going and flesh out this way of potentially doing it (such a USE_EXPAND was idly mentioned at start by others as something that was deemed too crazy, but I didn't find any references). It is currently still as a draft over at http://piratepad.net/iwvgjB1P5d - but I didn't want the original USE=gui thread to discuss this, as it's a separate and much more complex matter really, and would work in tandem with USE=gui when appropriate. > It's the implementation that gets me here, not the idea. The idea > could > be neat and make Gentoo management easier at the expense of some > (hopefully) minor ebuild bloat. Another issue that hasn't been > covered > well yet is how are we going to select DEPENDs? I was told DEPEND > doesn't support exactly-one-of, and we don't want extraneous > dependencies. The part of it being not clear (due to the intentional lack of REQUIRED_USE usage in that design) what is getting built is probably the main drawback of that drafted idea, and some QA members tell me this would be outright vetoed as a QA violation. This uncertainty also echoes in the need for these complex DEPEND atoms as well then, based on maintainer chosen preference, combined with user set flags. So it isn't ideal at all indeed, and we'd need to really do the suggested EAPI/package manager improvements first, to express this maintainer order of preference to the user and filter the flags somehow to what will actually be chosen then before the DEPEND atoms get processed, which would make the *DEPENDs feasible, as you could simplify the conditionals, because the unused (but set by user) USE flags are already filtered out then (or one added when user didn't have any, and one would be chosen by default). I ruled out REQUIRED_USE because I don't like it at all when it is used together with common global USE flags, as opposed to just some local flags. In my opinion it tends to results in users disabling or enabling something globally, instead of locally for the package in question. And with that having made the choice unknowingly for a ton of future packages to be installed as well. pkg_pretend is a bit better, because you can customize the error message to be readable, but it's still something that takes away my choice of not having to care.. just give me a GUI, preferably a gtk3 one, ok? thx. > Transmission is a good example: supports gtk3, qt4, qt5. Let's say > the > maintainer prefers the qt5 version. Would we do this?: > > DEPEND="gui_qt5? ( dev-qt/qtcore:5 ) gui_qt4? ( dev-qt/qtcore:4 ) > gui_gtk3? ( x11-libs/gtk+:3 )" > > or this?: > > DEPEND="gui_qt5? ( !gui_qt4? ( !gui_gtk3? ( dev-qt/qtcore:5 ) ) )" > > (snipping because I don't feel like writing it all out) Transmissions is a good example indeed, but not in the way you describe here, because transmission can be built with gtk and qt in parallel. So it's a good example of what a hypothetical EAPI-next markup for describing this order of choices would have to support. qt4 or qt5 or neither is one choice. gtk2 or gtk3 or neither another. And none of them have to be there, so if USE=-gui, GUI="..." is ignored, but with USE=gui and GUI="<empty>" a qt5 choice would be made. I wonder if the same syntax as REQUIRED_USE can be used for expressing this, sans order of priority (unless it can be implicit from the order of things listed). If we had some way to express this, similar to REQUIRED_USE, that part could take care of simplifying the DEPEND to "gui? ( gui_qt5? ( dev-qt/qtgui:5 ) gui_qt4? ( dev-qt/qtgui:4 ) gui_gtk3? ( x11-libs/gtk+:3 ) gui_gtk2? ( x11-libs/gtk+:2 ) )" if it would override the flags to what will be chosen for us already at this point via some markup like GUI_PREFS="gui? ( || ( ?? ( gui_qt5 gui_qt4 ) ?? ( gui_gtk3 gui_gtk2 ) ) )" if we can default to the first of each branch of choice, or something more complex to sequence these choices. This could also probably be achieved one way or another via an eclass (or maybe not - the rules of global variables like *DEPEND are rather strict and I'm not sure you can influence them sufficiently via an eclass), but that doesn't solve the issues of package manager not really knowing what happened (apparently bad for binary packages), and the user not knowing what's going on without reading the ebuild. Brainstorming welcome on this, but a medium like IRC might be more constructive at this point for that purpose. Mart
