I really would to see something like this on elixir. I suggested something 
really similar, the addition of an `fetch_env!` function to the System 
module. 
https://groups.google.com/forum/#!msg/elixir-lang-core/gijvoPm-a-0/Y2TzcHaiBgAJ


Em sexta-feira, 1 de março de 2019 14:03:03 UTC-3, Fl4m3Ph03n1x escreveu:
>
> Background
> I know this was proposed before and refuted: 
> https://github.com/elixir-lang/elixir/issues/5608
>
> However, I recently had an issue that would have benefited from 
> System.get_env! and was advised to create a proposal in this group and 
> reopen the discussion.
>
> What was the issue?
> Imagine you have a config.exs where you define some configurations. 
> Imagine one of the configurations is the following:
>
> config :my_app,
>   geolix_db_path: System.get_env("PROJECTS_PATH") <> 
> "/my_app/lib/geoip/GeoLite2-Country.mmdb"
>
> Now this may look normal, but what if you don't have the "PROJETCS_PATH" 
> variable defined? 
> What error do you think you would get?
>
> We got this:
>
> ** (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
>
> What now?
> If you find this error message borderline useless and beyond cryptic, then 
> you are with me. 
> The problem is that the stacktrace is obfuscated while the config file is 
> being evaluated. 
>
> The WHY of the proposal
> A way of avoiding this would be to have a System.get_env! that blows 
> immediately making the error very clear. 
> I know I can use || raise "error" but I would like to avoid that every time I 
> use System.get_env in a config file (or somewhere else  for that matter).
>
> Have you imagined what is like reading a config.ex file hundreds of lines 
> long while using the || raise trick? 
> We already have trouble managing our huge config files, adding this would 
> make it even worst.
>
> Additional info
> This discussion was generated from the forums. The original post with all the 
> information can be seen here:
>
> https://elixirforum.com/t/mix-exs-does-not-compile/20516
>
>

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