Since I was just struggling with the same annoying problem, thank you, @dustinfarris, for preventing the vein on my forehead from bursting, and @windholtz for asking the question.
I wish Phoenix would use Webpack 2 as its default build tool. Brunch’s documentation is just awful and the path structure is really confusing. Code splitting is also a lot less of a problem with Webpack 2.
Sorry to resurrect an old discussion, but I was using the posts here for reference and had a query:
How come there are two “output directories” for the Elm code:
paths: {
...
public: "../priv/static"
},
and (from @windholtz’s repo):
elmBrunch: {
...
outputFolder: "../assets/js"
}
Also, it seems like there’s a case of “the chicken and the egg” here - js/app.js seems to be built before the main.js that is built from main.Elm. It fails the first time, then succeeds because main.js now exists, though I suspect will always be one compile behind.
Also, it seems like there’s a case of “the chicken and the egg” here - js/app.js seems to be built before the main.js that is built from main.Elm. It fails the first time, then succeeds because main.js now exists, though I suspect will always be one compile behind.
I also have this problem. It prevents me from adding the generated elm.js to .gitignore so I have a big ugly js file in my git repo. Not sure how to tell phoenix to compile elm.js before running app.js.
That is mostly just because the elm plugin for brunch is borked. If you drop brunch or make a custom plugin or so then it could be fixed.
That temporal ordering problem between app.js and the Elm compilation step is a real pain, especially for a Phoenix noob like me. Seeing the popup notification on my desktop like 10 seconds later is a further insult 
It would certainly seem neater to go with Webpack or even just NPM as the build tool.
@Desty @Most that compilation order bug in elm-brunch was introduced in this PR: Make compilation in onCompile hook instead of compile method by stelmakh · Pull Request #30 · madsflensted/elm-brunch · GitHub.
There is an open issue on it since March but I don’t think the maintainer is active right now. The easiest fix is specify the previous version - 0.7.0 in your package.json.
Glad I’m not the only one. New to Phoenix and Elm I thought I was just being stupid or the instructions I was following when trying to set it up were buggy. Turns out it’s a change in the Phoenix directory structure that 1.3 brought that was causing the instructions not to work.