What are IntelliJ's requirements for supporting code formatting for a language?
Supposedly the Haskforce plugin does formatting via an external tool (https://github.com/avh4/elm-format/issues/182#issuecomment-230946090), can that approach be used for the elm plugin? Does the elm plugin author not like that approach, and if so, could a separate elm-format plugin be created?
What API needs to be implemented in the IntelliJ plugin?
How can we generate the required formatting code from the elm-format source?
Questions to answer: