Starting mix task process dependencies

Question

New to Elixir but loving it so far :)

A lot of my mix tasks depend on HTTPotion.

My mix.exs file is declared as such

  def application do
    [
      applications: [:logger, :cowboy, :plug, :httpotion, :poison],
      mod: {BiddingAgent, []}
    ]
  end

So HTTPotion.start is called automatically. However, when I run a task like mix campaign.list which needs to call an http request, I have to manually call HTTPotion.start.

What is the idiomatic way to make sure the right processes are started for my mix tasks?

Thanks!

Answer 1

You're right, when starting the app outside of the startup script you do need to start the dependencies manually.

I prefer to call the Application module instead of each dependency directly.

Add the following code to the run function inside your task module.

{:ok, _started} = Application.ensure_all_started(:httpotion)

If you have any doubt you can take a look at the documentation

Edit: The practice described is being used in Ecto

• https://github.com/elixir-lang/ecto/blob/master/lib/mix/ecto.ex#L73

• https://github.com/elixir-lang/ecto/blob/df13b1c64f8edd128cec1316336b20f3153eafa3/lib/mix/tasks/ecto.migrate.ex#L67

A module is included in a the mix tasks which provides an ensure_started method.