Well, looking at the blocking bug the question here is more a clarification right? 

IMHO, if the required packages is currently installed or in the current proposed group transaction then the conditional package should also be installed.

Yes, first of all it's about clarification. On the other hand, this turned out to be quite important feature which can't stay undocumented.

> IMHO, if the required packages is currently installed or in the current
> proposed group transaction then the conditional package should also be
> installed.

So you basically mean that during the installation of group A and B the group members are checked for presence of required pkgs. And conditional packages are consequently added into transaction if some other group in transaction contains their requirements, right? Please be aware that this happens before resolving and does not take into account mixing group and pkg installation (dnf install pkg @group).

Lets take an example from comps
<packagereq type="conditional" requires="xorg-x11-server-Xorg">ibus-m17n</packagereq>

I have rread through yum/comps.py for some background knowledge 

yum/__init__.py has 
            if not lupgrade and group_conditionals:
                for condreq, cond in thisgroup.conditional_packages.iteritems():
                    if self.isPackageInstalled(cond):
                        try:
                            txmbrs = self.install(name = condreq)
                        except Errors.InstallError:
                            # we don't care if the package doesn't exist
                            continue
                        else:
                            if cond not in self.tsInfo.conditionals:
                                self.tsInfo.conditionals[cond]=[]


which I read as if group_conditionals is enabled, it can be enabled or not.
if xorg-x11-server-Xorg is in the transaction then we should try and install ibus-m17n

I did not dig into the code to see if txmbrs is only packages in the transaction or includes packages that are already installed. but I am assuming the former.


Fully documenting comps will take a lot of work and effort that is useful but I do not know of many people with the knowledge of it or the time to do the work. It does need to be done but it will involve digging throough yum's code to document all the corner cases. If you have some resources to do that work it would be appreciated.

notting would be the obvious person to ask, since comps was always his baby...

my understanding of 'conditional' for comps, FWIW, is this. If a package 'foo' is in comps group 'A' and it is marked as 'conditional' for package 'bar', that means that 'foo' should also be installed if *both* group 'A' is selected for install *and* package 'bar' is selected for install (or already installed).

This bug appears to have been reported against 'rawhide' during the Fedora 26 development cycle.
Changing version to '26'.

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