pkg/56251: meta-packages are fragile

[dholland%NetBSD.org@localhost]

>Number:         56251
>Category:       pkg
>Synopsis:       meta-packages are fragile
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    pkg-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 16 23:30:00 +0000 2021
>Originator:     David A. Holland
>Release:        pkgsrc 20210616
>Organization:
>Environment:
n/a
>Description:

Large meta-packages, such as the ones associated with desktops, are
fragile for binary package users, in that if anything at all anywhere
in the dependency tree fails the meta-package is not built and is
unavailable in that build's binary packages. It's then impossible to
use the meta-package as a handle for installing the intended software,
even though most of it is available and the bust bits might be of no
interest whatsoever.

This inconveniences and confuses users.

>How-To-Repeat:
	See for example PR 51235.
>Fix:

This has been argued about periodically with no conclusions. One
option though is to introduce weak dependencies, which would be
dropped at build time if they fail. However, this would at a minimum
need to be taught to pbulk as well as implemented in the
infrastructure; and it might be necessary to tag these depends weak in
binary packages as well to prevent pkgin from accidentally doing silly
things. (E.g. if some KDE app breaks and gets dropped from the
metapackage, it's possible that without intervention pkgin would
autoremove the prior still-working copy at update time...)