"+" is an acceptable character in apt package names

[larskanis]

... and there are actually packages like "g++", which were cut to package "g"

[MSP-Greg]

@larskanis

Thanks, good catch. I looked thru the MSYS2 packages I have installed locally; I couldn't find one with a + character. Also, looked at the current vcpkg ports, and couldn't find one. Both use the common.js function:

setup-ruby-pkgs/common.js

Line 100 in 48dadf0

export const getInput = (name) => core.getInput(name).replace(/[^a-z_ \d.-]+/gi, '').trim().toLowerCase()

So, as you've done, I think the plus is probably best just added to apt-get. By change, do you run macOS? The @ character is added to its regex, not sure why I did that? Also not sure whether + should be added for brew?

[larskanis]

homebrew has "+" characters in the package names as well: https://formulae.brew.sh/formula/libxml++3