/builddir/build/ does not get cleaned between builds when 'mock --chain' is used with an external remote-mount

[tom-crane]

I am rebuilding multiple SRPMs using,

mock --no-clean -r alma+epel-9-x86_64 --enablerepo=devel --localrepo=$REPOID --chain $SRPMLIST

which works fine. I am using --no-clean because I customise the choot before starting the mock build.

My problem is I don't have enough disc space on the local /var FS for the buildroot under /var/lib/mock but do have an NFS server with more storage. Mounting the remote server with these options,

config_opts['plugin_conf']['mount_enable'] = True
config_opts['plugin_conf']['mount_opts']['dirs'].append(("nfsstore1:/mock_scratch", "/builddir/build", "nfs", "rw,hard,bg,noatime,tcp"))

in ~/.config/mock.cfg appears to do the trick with mock using the remote /builddir/build/ and populating it with the usual {BUILD,BUILDROOT,originals,RPMS,SOURCES,SPECS,SRPMS} directories as expected.

The problem is that after finishing the first package, mock does not remove the /builddir/build/ tree as it does when using local storage. When it attempts to build the 2nd, 3rd etc. packages those builds fails with,

ERROR: Expected to find single rebuilt srpm, found 2 in /var/lib/mock/alma+epel-9-x86_64/root//builddir/build/SRPMS/*src.rpm
ERROR: Expected to find single rebuilt srpm, found 3 in /var/lib/mock/alma+epel-9-x86_64/root//builddir/build/SRPMS/*src.rpm
ERROR: Expected to find single rebuilt srpm, found 4 in /var/lib/mock/alma+epel-9-x86_64/root//builddir/build/SRPMS/*src.rpm

etc.

because the source RPMs from previous builds remain in /builddir/build/SRPMS/.

Is this a bug or am I making a configuration mistake? Are there any work-arounds?

Thanks
Tom Crane