I think a simpler alternative to an `as` option might be:
`System.get_boolean_env/1` and `System.get_integer_env/1` that return things
like:
`{:invalid, value}` when the value can’t be parsed, but provide ! versions that
raise errors, i.e
```elixir
config :something, port: System.get_integer_env!(“SERVER_PORT”)
```
Raising something like
```elixir
Expected SERVER_PORT to be an integer, got <something>
```
> On Feb 18, 2025, at 11:15 AM, Cocoa Xu <i...@uwucocoa.moe> wrote:
>
> This would be quite helpful to deal with environment variables that are
> expected to be boolean or integers. In my experience, I always have to
> copy-paste a helper function to do the type cast:
>
> defp to_boolean(nil), do: false
>
> defp to_boolean(var) when is_boolean(var) do
> var
> end
>
> defp to_boolean(var) do
> String.downcase(to_string(var)) in ["1", "true", "on", "yes", "y"]
> end
>
>
> On Tuesday, February 18, 2025 at 5:07:50 PM UTC+1 dave.lu
> <http://dave.lu/>...@gmail.com <http://gmail.com/> wrote:
>> In Elixir applications, config/runtime.exs is often used to parse
>> environment variables from System.get_env2/ and friends, and convert into
>> Application configuration.
>>
>> Since environment variables can only be strings, it is often necessary to
>> cast from string values into booleans and integer values. E.g.
>>
>> config :my_app, :bool_value, System.get_env("BOOL_VALUE") == "true"
>>
>> config :my_app, :int_value, String.to_string(System.get_env("INT_VALUE",
>> "5"))
>>
>> While there are entire libraries that deal with advanced runtime
>> configuration, like Vapor <https://github.com/elixir-toniq/vapor> and
>> elixir-specify <https://github.com/Qqwy/elixir-specify>, I believe there is
>> an opportunity to simplify common patterns and duplicative code in Elixir
>> configuration that often leads to confusion and edge case issues.
>>
>> My proposal is to add parsing for both booleans and integers to environment
>> variable parsing. As an example:
>>
>> config :my_app, :bool_value, System.get_env_as!("BOOL_VALUE", "false", as:
>> :boolean)
>>
>> config :my_app, :int_value, System.get_env_as!("INT_VALUE", "5", as:
>> :integer)
>>
>> The trickiness would be in the acceptable range of edge case values. For
>> example, "1" and "0" are often used for boolean values, in addition to
>> "TRUE" and "FALSE". I believe there could be a reasonable compromise and
>> appropriate documentation for addressing these issues.
>>
>> More complex parsing, such as floats and custom data types would not be
>> supported.
>
>
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