A Configuration Provider source based on System.get_env/2

Values will be loaded based on #{prefix}_#{capitalized_field_name}. prefix defaults to the capitalized name of the configuration specification module. capitalized_field_name is in CONSTANT_CASE (all-caps, with underscores as word separators).

Examples

The following examples use the following specification for reference:

defmodule Elixir.Pet do
  require Specify
  Specify.defconfig do
    @doc "The name of the pet"
    field :name, :string
    @doc "is it a dog or a cat?"
    field :kind, :atom, system_env_name: "TYPE"
  end
end

Note that if a field has a different name than the environment variable you want to read from, you can add the system_env_name: option when specifying the field, as has been done for the :kind field in the example module above.

iex> System.put_env("PET_NAME", "Timmy")
iex> System.put_env("PET_TYPE", "cat")
iex> Pet.load(sources: [Specify.Provider.SystemEnv.new()])
%Pet{name: "Timmy", kind: :cat}
iex> Pet.load(sources: [Specify.Provider.SystemEnv.new("PET")])
%Pet{name: "Timmy", kind: :cat}

iex> System.put_env("SECOND_PET_NAME", "John")
iex> System.put_env("SECOND_PET_TYPE", "dog")
iex> Pet.load(sources: [Specify.Provider.SystemEnv.new("SECOND_PET")])
%Pet{name: "John", kind: :dog}