Hmmm, I wonder if that error message could be improved to guide users to the correct fix for their needs. At the very least I believe we can say that when only html is specified in render_errors that only an iolist or binary are valid inputs and other inputs should result in an error message.

Not the view name but rather what ‘higher up’ in the callstack is calling your render function. In a base error rendrerer there’s very little above it and I’m not sure if the content-type requested by the client is followed or not (since it’s an error and the body shouldn’t be used for data anyway).

You can always return the stacktrace in that function and see what it’s going through, there might be an option?

Edit: Googled a bit and the Phoenix View documentation shows rendering JSON from a map in an example. So it should work.

That’s for rendering from controllers, not errors though, I’m unsure about error handling.

I’m curious what the content-type is of the response then.

@OvermindDL1 as far as I can tell, the error view is set as a config option on the endpoint (render_errors) where you can specify a list of content types. Generating a fresh phoenix app with no HTML gives you an error view that has this comment

  # If you want to customize a particular status code
  # for a certain format, you may uncomment below.
  # def render("500.json", _assigns) do
  #   %{errors: %{detail: "Internal Server Error"}}
  # end

so I see no reason why returning maps wouldn’t work here either.

In fact, @benonymus, I’m curious what your render_errors config option looks like in config/config.exs, config/dev.exs and config/prod.exs. Maybe you’ve put JSON in one and HTML in another? It should look something like this

render_errors: [view: HelloWeb.ErrorView, accepts: ~w(json)],