ember-data.js: https://github.com/emberjs/data/tree/0396411e39df96c8506de3182c81414c1d0eb981
In short, when there is an error, I want to display error messages in th
DS.RESTAdapter just got a bit more error handling in this commit but we are still not yet at a point where we have a great recommendation for error handling.
If you are ambitious/crazy enough to put apps in production today with ember-data (as I have been!), it is best to make sure that the likelihood of failures in your API is extremely low. i.e. validate your data client-side.
Hopefully, we can update this question with a much better answer in the coming months.