Hi, While writing and using some ebuilds, I had to deal with (pseudo) USE flags requirements. For example, if you install mplayer with USE="encode" the result will depend on other USE flags: if you have USE="encode mp3", it will install lame for example. I know a few ebuilds behave like that in the tree. We can also see some ebuilds that will force an option if you set another one: if you set USE="-foo +bar" and bar needs foo, it will silently set --enable-foo. Finally, they are some ebuilds like >=ekiga-3 that will just fail if you have two USE flags "conflicting": kontact needs kde so USE="kde -kontact" and USE="kde kontact" are okay but USE="-kde kontact" will fail.
In my opinion, we can't keep auto-enabling some options because the user has enabled another option without telling him and without telling the package manager. For example, I'm a lambda user, I've set USE=kontact but I don't know it's related to KDE, I don't have a KDE desktop and I don't want one. With the regular behavior in the tree, kde will be enabled silently and the user will don't have a clue about it like the package manager. This last one is even worst because if we imagine a library ebuild with this behavior used by other ebuilds in the tree, EAPI-2 use dependencies will break. (foo ebuild depends on ekiga[kde], user will have to rebuild ekiga if it has been built with USE="-kde kontact" even if ekiga has been built with kde support or foo ebuild depends on mplayer[mp3] should be mplayer[encode,mp3]. However, dying is probably not the best solution too. So I think we should add a new feature in PMS already used in Exherbo EAPI, USE flags requirements [1]. That means an ebuild should be able to say a USE flag is available only if some other ones are in a specific state. Let's take the mplayer example, if we have a line like this: USE_REQUIREMENTS="encode? ( mp2 mp3 faac x264 xvid )", PM should be able to show the user USE="mp3" will be ignored because he didn't set USE="encode" and the PM will disable this USE flag by himself. The same way, for ekiga: USE_REQUIREMENTS="kde? ( kontact )", PM should be able to show the user if he set USE="kontact", kde USE flag is enabled and the PM will enable this USE flag by himself. I think this new feature should help everyones life. We can also imagine great features like a minimal USE-flag that will be something like: USE_REQUIREMENTS="minimal? ( foo bar )" to set a list of USE flags to disable if minimal USE flag is enabled. Combined to EAPI-1 auto-enabled USE flags, it could help disabling all auto-enabled USE flags for some uses... That's just an idea. I'm not writing a GLEP draft so don't try to found an issue in the syntax used, it's only to know if this kind of feature will be appreciated by other users/devs than me and if it could be added to EAPI-4 and worth to work on it. I can write the GLEP and implement the feature in portage. [1] http://www.exherbo.org/docs/exheres-for-smarties.html#myoptions Thanks, Mounir
