How to install yarn via pacman without node
Background
I decided to install NodeJS not using pacman but using a version manager (nvm at the moment).
However, according to Yarn official, I should install Yarn itself via an OS package manager for several reasons. https://yarnpkg.com/en/docs/install#alternatives-stable
At last, I have to install yarn via pacman skipping its only dependency, nodejs.
Solution
pacman -S --assume-installed nodejs yarn