Mix.env() is nil on production

I added this to my base layout file:

<%= if Mix.env() in [:prod] do %>
    <!-- Global site tag (gtag.js) - Google Analytics -->
    <script async src="https://www.googletagmanager.com/gtag/js?........................
<% end %>

and it crashes on production because of supposedely being “Mix.env()” nil.

How to fix it?

It should crash because the moduleMix is unavailable.

Mix as a build tool is usually not included in production builds.

The proper way is to put something in the config and branch on that.

PS: it’s probably not prod you want to check but if debug is enabled. This way you can even name it properly.

1 Like

You could save Mix.env() into a module attribute and use it in your app, e.g.

defmodule App do
  @env Mix.env()
  def env, do: @env

This will embed your Mix.env info into your compiled app.


@kattair0ta8 you can prepare your code to check Code.ensure_loaded?(Mix) (on prod not loaded). But I recommend save in config env settings like


config :my_app, env: :prod

This enable in code check Application.get_env(:my_app, :env) == :prod