elm-mode can't compile file

Question

When creating projects with elm init, elm creates a project structure where there is a elm.json in the root of the project directory and a src folder, where your .elm files should go

Elm-mode for emacs doesn't seem to support this. When visiting a file in the src directory and typing C-c C-c to compile the file, I get the following error:

-*- mode: elm-compilation; default-directory: "~/Projects/select-elm/src/" -*-
Elm-Compile started at Mon May 13 04:29:55

/home/chris/.nvm/versions/node/v8.9.3/bin/elm make Main.elm --output\=elm.js
-- FILE NOT FOUND --------------------------------------------------------------

You want me to compile this file:

    Main.elm

I cannot find it though! Is there a typo?


Elm-Compile exited abnormally with code 1 at Mon May 13 04:29:56

This is the same error you get when calling elm make Main.elm from the command line in the src folder instead of in the root folder of the project.

If this same file is saved to the root folder of the project, C-c C-c compiles the file without errors. It seems elm-mode expects source files to be directly in the root directory of a project, while the elm language convention is to save the source files in the src folder.

I'm using elm 0.19.0. Is there a graceful way to make elm-mode "project aware", or something similar?

Unfortunately I don't have the option of simply saving my files to the root folder of the project because this is not a project that I own.

Answer 1

It took me a while to figure this one out, posting to help future users.

Elm-mode uses by default "elm-package.json" to find the root directory of your project. This was the value used in Elm 0.18 and changed in 0.19 to "elm.json".

Just customize the variable elm-package-json and set it to "elm.json".

For example (setq elm-package-json "elm.json")

This is described in elm-util.el