Solved by modularity team (you have the macros package for free).

Btw., this has already been rejected -- follow the https://bugzilla.redhat.com/show_bug.cgi?id=1415802

mock supports passing arguments for rpmbuild for long time and it's really painful when you want to pass --with python3 or something like this to build.. You have to create -macros package, make sure that it installed in buildroot and then build your package. This takes ages =(
Koji doesn't implement this (yet?), so COPR might be good place to try it out (one extra feature) :)

Do you have a concrete idea about user interface for this or is any implementation good?

Koji won't provide the functionality; that would allow packagers doing unpredictable builds.

@praiskup
1. It was not solved by modularity, you can't build macros package over and over because it takes ages
2. It is just not user-friendly and do not help usual people (who are not interested in modularity)
3. Koji just need to store that information somewhere in DB and that should be pretty much it, solution always exist

@clime
probably just some free text field when submitting build where people can specify whatever they want and it will be passed to --rpmbuild-opts?

1. Koji just need to store that information somewhere in DB and that should be pretty much it, solution always exist

ditto for copr; and have you tried to talk about this with Koji devels ;) ?

I mean, because Koji devels always refused to implement this -- modularity team has invented their own way to provide the options through macros: https://pagure.io/modulemd/issue/34

@praiskup so I think you are a bit wrong that koji rejects to add this functionality -- see https://pagure.io/koji/issue/505

@ignatenkobrain 6 months old issue? You need to wait another 72 months for WONTFIX :). Allowing this functionality (for non-admin user) would make unpredictable build results; maintaining build options in git && some external database would much complicate distribution maintenance, provenpackager work, mass-rebuilds, etc. (I'm not koji maintainer, but I would probably refuse this feature if I was in that role).

mock supports passing arguments for rpmbuild for long time and it's really painful when you want to pass --with python3

Hello, we implemented just exactly this and it is now in production available in a chroot settings.

https://pagure.io/copr/copr/c/760a23b24eeb01cd79410d60d9f21e1d7fde1c7d?branch=master
https://pagure.io/copr/copr/c/3322a4a4dcce39dae2b607f5da979e2d5e7908f2?branch=master

And it's naive implementation, unfortunately - even though I pointed that out; I wish @clime also went through pull-requests, as everybody else does...

There are dozens of mock options, and we might well re-implement every-single option this way in copr. No, please add generic field (if anything) which allows us to set any mock option. This is just api bloat.