pkg_stats.fish

function get_packages
	pacman -Qq
end

function get_exec_from_package --argument-names pkg
	set -l lines (pacman -Ql $pkg | string match -r "/usr/bin/(.+)|/usr/sbin/(.+)")
	while set -q lines[2]
		echo $lines[2]
		set -e lines[1..2]
	end
end

set -l count_total 0
set -l count_matching 0
set -l count_total_fishcompleted 0
set -l count_matching_fishcompleted 0
for pkg in (get_packages)
	for cmd in (get_exec_from_package $pkg)


		set count_total (math "$count_total + 1")
		if test $cmd = $pkg
			set count_matching (math "$count_matching + 1")
		end


		if test -e /usr/share/fish/completions/$cmd.fish
			set count_total_fishcompleted (math "$count_total_fishcompleted + 1")
			if test $cmd = $pkg
				set count_matching_fishcompleted (math "$count_matching_fishcompleted + 1")
			end


			echo + $cmd $pkg
		else
			echo - $cmd $pkg
		end
	end
end

echo $count_matching $count_total
echo $count_matching_fishcompleted $count_total_fishcompleted

A few comments:

• get_packages can be simplified to pacman -Qq.

• get_exec_from_package can also be simplified with pacman -Qlq (so it doesn't print the package name anymore, so you don't need a capturing group). pacman -Qlq | string match -r "/usr/bin/.+" should work (the sbin is also superfluous on arch).

I wasn't expecting that, but I like the fact that you took the time to comment on this code. :-)