On Fri, Mar 26, 2021 at 8:45 AM Robert P. J. Day <rpjday@...> wrote:

what should be easy questions about packagegroups, inspired by my
running across some puzzling packagegroup recipes in my travels
recently. (i'll start with examples out of oe-core).

first, as with any other recipe, given a "trivial" packagegroup
like, say, packagegroup-core-eclipse-debug.bb:

SUMMARY = "Remote debugging tools for Eclipse integration"

inherit packagegroup

RDEPENDS_${PN} = "\
gdbserver \
tcf-agent \
openssh-sftp-server \
"

there is no need to add a "PROVIDES" line since every recipe file
automatically provides its own name. so far, so good.

if we move up to packagegroup-core-nfs.bb, note how this recipe file
defines two additional packagegroups, and has to add a PROVIDES line
in order to make those new names accessible:

PROVIDES = "${PACKAGES}"
PACKAGES = "${PN}-server ${PN}-client"

SUMMARY_${PN}-client = "NFS client"
RDEPENDS_${PN}-client = "nfs-utils-client"

SUMMARY_${PN}-server = "NFS server"
RDEPENDS_${PN}-server = "\
nfs-utils \
nfs-utils-client \
"

so the question is, must one supply a PROVIDES line for any
packagegroup names above and beyond the one that comes with the recipe
file itself? i ask what seems like a dumb question as i've run across
packagegroup recipe files that define multiple additional
packagegroups, but do not add them to the PROVIDES line. what is that
supposed to represent?

PROVIDES sets up a name which can be used as DEPENDS (ie a build time
dependency) in other recipes. If PROVIDES contains more than one name,
they all just become aliases for each other.

Since packagegroup recipes only define run time dependencies, nothing
should have a build time dependency on a packagegroup recipe... and so
there's no obvious reason to set PROVIDES to anything. Leaving the
default will be fine (although it won't be used for anything).