ebegin: Output QA warning if call to eend is missing

[laumann]

The idea here is to check if EBEGIN_EEND is set after the phase has been
executed. If so, then a call to eend is probably missing. This is under
the assumption that ebegin-eend invocations should be properly paired
within the same phase.

In ebegin, the EBEGIN_EEND variable is also checked, and, if set,
indicates that ebegin has been called and is missing the closing call to
eend.

I doubt that this check is perfect, but it seems to work in what little
testing I've done.

Closes: https://bugs.gentoo.org/835823
Signed-off-by: Thomas Bracht Laumann Jespersen t@laumann.xyz

[laumann]

For the sake of completeness, here's the very simple ebuild I've tested with:

# Copyright 2022 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

EAPI=8

DESCRIPTION="Testing package"
HOMEPAGE="http://nowhere.com"

LICENSE="GPL-2"
SLOT="0"

pkg_pretend() {
	ebegin "well hello there"
	ebegin "well hello again"
}

pkg_setup() {
	eend 0
}

and the output:

$ ebuild dev-libs/foobar/foobar-0.0.1.ebuild clean setup
Appending /home/tj/sources/gentoo/portage-tester to PORTDIR_OVERLAY...
 * well hello there ...
 * well hello again ...
 * QA Notice: ebegin called, but missing call to eend (phase: pretend)
 * QA Notice: ebegin called, but missing call to eend (phase: pretend)
 * QA Notice: eend called without preceding ebegin (phase: setup)
 [ ok ]

[zmedico]

LGTM