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

[Peter Kjellerstedt]

> -----Original Message-----
> From: openembedded-core-bounces at lists.openembedded.org <openembedded-core-
> bounces at lists.openembedded.org> On Behalf Of Robert P. J. Day
> Sent: den 1 mars 2020 12:51
> To: OE Core mailing list <openembedded-core at lists.openembedded.org>
> Subject: Re: [OE-core] is there ever a compelling reason for
> "FILESEXTRAPATHS_append := ..."?
> 
> 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

Although contradictory to logic, it is apparently correct to use 
"<path>:" both with _prepend and _append when adding to 
FILESEXTRAPATHS (see the default value set by bitbake.conf, which is 
"__default:"). However, problems _will_ arise if different bbappend 
files for the same recipe do it differently... It can also be noted 
that the QA test in insane.bbclass suggests to use ":<path>" with 
_append, further adding to the confusion.

> 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"?)

No, ${COREBASE} is correct. (OEROOT is not a bitbake variable, it is 
only available in the oe-init-build-env script.)

> 
> rday

//Peter