The Atom Elixir Formatter recently changed the way it communicates with the Elixir code formatter. It now uses the - option added to the Elixir master branch on October 17, 2017. This allows formatting via STDIN and STDOUT, which eliminates temporary files and reduces latency.

IMPORTANT If you downloaded and compiled the master branch of Elixir prior to that date, you will need to update your local Elixir repo and recompile. Please visit atom-elixir-formatter more information.