Elixir: ** (ArgumentError) argument error on every invocation of Mix

[raarts]

This only happens within my project tree, but I don't know how to troubleshoot it. The error is not very informative.

Environment

• Elixir & Erlang/OTP versions (elixir --version):

Erlang/OTP 21 [erts-10.1.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]

Elixir 1.7.4 (compiled with Erlang/OTP 21)

• Operating system: MacOS Mojave 10.14.1 (18B75)

Current behavior

$ MIX_DEBUG=true mix help
** Running mix loadconfig (inside Api.Umbrella.MixProject)
** (ArgumentError) argument error
    (stdlib) eval_bits.erl:101: :eval_bits.eval_exp_field1/6
    (stdlib) eval_bits.erl:92: :eval_bits.eval_field/3
    (stdlib) eval_bits.erl:68: :eval_bits.expr_grp/4
    (stdlib) erl_eval.erl:484: :erl_eval.expr/5
    (stdlib) erl_eval.erl:888: :erl_eval.expr_list/6
    (stdlib) erl_eval.erl:240: :erl_eval.expr/5
    (stdlib) erl_eval.erl:232: :erl_eval.expr/5

Expected behavior

it should work.

Here's my mix.exs:

defmodule Api.Umbrella.MixProject do
  use Mix.Project

  def project do
    [
      apps_path: "apps",
      start_permanent: Mix.env() == :prod,
      deps: deps()
    ]
  end

  # Dependencies can be Hex packages:
  #
  #   {:mydep, "~> 0.3.0"}
  #
  # Or git/path repositories:
  #
  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
  #
  # Type "mix help deps" for more examples and options.
  #
  # Dependencies listed here are available only for this project
  # and cannot be accessed from applications inside the apps folder
  defp deps do
    [
      {:coverex, "~> 1.5.0", only: :test},
      {:credo, "~> 0.10.0", only: [:dev, :test], runtime: false},
      {:distillery, "~> 2.0"}
    ]
  end
end

[josevalim]

Hi @raarts, that should work indeed. :) I pasted the mix.exs file locally and it did it work. What is in your config/ files? In case you can't share it, because it has secrets and other stuff, does it work if you remove the config directory?

[raarts]

Alright, that fixes it. And helped me find the problem:

config :api_web, :myapp,
       app_id: System.get_env("OIDC_RESOURCE"),
       app_url: System.get_env("OIDC_BASEURL") <> "/" <> System.get_env("OIDC_REALM")

Of course the env var was not there. I make stupid errors all the time. Thanks for pointing me into the right direction.

[josevalim]

@raarts this error message is super bad though. We will look into improving it directly in Erlang/OTP. Thanks!

[SampsonCrowley]

@josevalim still the same unhelpful error message in 1.9

[trbngr]

Same message here too.

Turns out you can't concat strings with <> in a config file.

[SampsonCrowley]

@trbngr you can concat strings, what you can't do is concat nil with a string using <> which is what happens with the default phoenix config. the easiest fix is to always use the fallback syntax: System.get_env("APP_NAME", "fallback-value")