I've created an eclass of primary use to overlay developers that I'm using in my own Gentoo-based system. It allows a package to essentially "inherit" the properties of another existing package, much in the same way as one might inherit from a superclass in an object-oriented programming language. The eclass is very rudimentary (hence "Prototype for"), but I think it can be useful to other people, and that if someone wants to clean it up (or there's enough interest that someone ask me to clean it up), it could go in the main Portage tree. I am attaching the actual eclass along with a couple of example ebuilds to show its usage.
Created attachment 88110 [details] override.eclass This is the override eclass. It provides two primary functions for use by inheriting ebuilds: override() and alongside(). The only difference between the two is that override() adds the overridden package as a block to the RDEPEND variable, i.e. it does not allow the overriding package to coexist with the overridden package on the system. The argument to override() or alongside() is the full name of a package ("category/packagename") without a version number; the override eclass will only override an ebuild with the exact same version number ($PVR) as the overriding ebuild. All global variables (IUSE, DESCRIPTION, SRC_URI, etc.) are imported into the current ebuild. The new variables OVERRIDE_PN, OVERRIDE_P, OVERRIDE_PF, and OVERRIDE_FILESDIR are set to the equivalent values of these variables in the target ebuild (and all references to ${PN}, ${P}, etc. in the target ebuild are modified to reflect these override variables). The variable S is defaulted to "$WORKDIR/$P", although it will take the value set in the target ebuild if there is one. All functions are imported, but the Portage functions (pkg_*, src_*) are imported with the names override_{pkg|src}_*. Any of these functions that are not defined in the overriding ebuild will take the value they would have from the target ebuild. To add to an existing function, define it and call override_{funcname} somewhere in the function.
Created attachment 88113 [details] sys-kernel/genkernel-selinux/genkernel-selinux-3.3.11d.ebuild This is an example of a simple ebuild that overrides an existing ebuild. In this case, it applies a couple patches (not included here) to the source and allows it to install normally.
Created attachment 88115 [details] sys-kernel/hardened-kernel/hardened-kernel-2.6.14-r8.ebuild This is a more complicated ebuild that can be installed alongside its target ebuild (hardened-sources). It changes the description and adds to the DEPEND and RDEPEND variables. It also completely overrides the src_compile and src_install functions (the latter being necessary for an alongside ebuild), as well as removing the bindings for the pkg_preinst and pkg_postinst functions by overriding them with empty functions.
Interesting trick- you've replicated what eclasses are about (a template for an ebuild), 'cept you missed the staleness checks :) Demonstration of the flaw- x overrides y. change x, emerge -s x, change y adding something new into the depends, then run emerge -s y (do _not_ touch x, else you'll trigger a regen). The new depends won't bleed through; this is why there is the inherit func, and INHERITED var- it tracks what eclasses were used, and triggers regeneration dependant on the timestamps involved for the ebuild _and_ the eclass. So... have to track what was pulled in. My suggestion? read through glep33, specifically package level eclasses; need the env saving protection that glep33 talks about to do this, but essentially you just define an eclass/template in the packages directory instead of the tricks you're doing. Meanwhile, this one it's an invalid...
marking invalid for ferringb.
pardon, screwed up the example slightly (yes I'm an idiot most days). foo-2 overrides/inherits bar-1, specifically doesn't change the description though. emerge -s foo bar; modify bar-1, changing the description emerge -s bar, note the description came through. emerge -s foo; note the description did *not* come through.
