On Mon, 10 Sep 2012 10:18:56 +0200 Fabian Groffen <grob...@gentoo.org> wrote: > Normally, if you use a USE-flag, you add them to IUSE of the ebuild. > However, some USE-flags have been considered too general to put them > in there in the past.
That's not exactly why. Historically (as in, way before EAPI days) IUSE was purely a visual thing: it was used for emerge -pv output, but not anything affecting behaviour. Thus, people didn't list things that weren't worth showing to the user. That all went out of the window when we got package.use, new-use support, etc. At that point, IUSE had to be fairly accurate. It became even more important when we introduced use dependencies and use dependency defaults. Not having an accurate IUSE means that dependencies like cat/pkg[prefix(-)] can't work. This is why the original EAPI 3 tidied all this up properly. Unfortunately, due to EAPI 3 becoming EAPI 4 and having some features removed, use dependency defaults ended up being "supported" without having the necessary information to make them work correctly in all cases, and prefix ended up being supported but without the "prefix" use flag being special. So really we should just not support prefix at all in any EAPI before 5, and not have the whole "but define those prefix variables anyway" hack in eclasses. But apparently people are preferring to go to great lengths not to have to use newer EAPIs... -- Ciaran McCreesh
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