[OE-core] is there ever a compelling reason for "FILESEXTRAPATHS_append := ..."?

[Robert P. J. Day]

On Sun, 1 Mar 2020, Robert P. J. Day wrote:

>
>   occasionally, i run across an existing bbappend file which contains
>
>   FILESEXTRAPATHS_append := ...
>
> and that makes me nervous as i don't see the rationale in *appending*
> to that variable in a bbappend file -- seems to defeat the purpose of
> potentially overriding what's in the original .bb recipe.
>
>   now, sometimes it's obvious that it's broken as i'm currently
> looking at an example:
>
>   FILESEXTRAPATHS_append := "${THISDIR}/${PN}:"
>
> which makes no sense at all with the colon at the end. but other than
> something so clearly broken, are there situations to append to
> FILESEXTRAPATHS? that just seems counter-productive, but maybe i'm
> missing something.

  figured i'd scan for examples of that in some of the many layers i
have checked out and found the following:

meta-boundary/recipes-qt/qt4/qt4-embedded_%.bbappend:FILESEXTRAPATHS_append
:= "${THISDIR}/files:"

meta-intel/recipes-core/zlib/zlib-intel_1.2.11.1.jtkv6.3.bb:FILESEXTRAPATHS_append
= ":${COREBASE}/meta/recipes-core/zlib/zlib"

meta-qt5/recipes-qt/qt5/qt5-ptest.inc:FILESEXTRAPATHS_append :=
":${THISDIR}/ptest"

meta-virtualization/recipes-networking/openvswitch/openvswitch_git.bb:FILESEXTRAPATHS_append
:= "${THISDIR}/${PN}-git:"

  note that a couple seem clearly(?) wrong (like that last one), but
i'm open to clarification as to when this is useful. (i think i see
the application in that meta-intel layer example, although should that
use "OEROOT" rather than "COREBASE"?)

rday