The Arch Linux package naming guidelines[1] specify that "package
names should consist of *alphanumeric characters only*; all letters
should be *lowercase*" (emphasis in original).
In reality, this guideline is not adhered to. In fact, *most* packages
have hyphens in their names, and some have a few other characters beyond
that.
This regex is used to parse the output of "pacman -Qu": '([\w-]+)
((?:\S+)-(?:\S+)) -> ((?:\S+)-(?:\S+))' [2] --- ie, we assume that
package names have only alphanumeric characters and hyphens. On the
other hand, the sanity check in makepkg (part of the distribution
itself) allows '[:alnum:]+_.@-' [3].
Boring story longer, Ansible broke for me today because pacman told it
it was going to upgrade "crypto++". Adding a plus to the first match
group of the regex above remedied the issue.
-Bruce
[1] https://wiki.archlinux.org/index.php/Arch_packaging_standards#Package_naming
[2] lib/ansible/modules/packaging/os/pacman.py:211
[3] /usr/share/makepkg/lint_pkgbuild/pkgname.sh:49 (on Archlinux)