MarsSeed [1] filed a deletion request for mpdproxy-coffeescript-git [2]: Broken, unused package. Fails to build. Upstream not maintained since 2020. [a]
Even if the needed makedepend is satisfied, the package is defunct: builds successfully, but does not install the needed mpdproxy executable. And btw the PKGBUILD executes 'npm install' inside prepare(). [a]: https://github.com/tremby/mpdproxy [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/mpdproxy-coffeescript-git/
