Exporting .env files does not behave same as loading file in Vapor with regard to empty strings

[tomjoro]

When a setting is exported from a .env file empty strings will appear in environment like this:

.env
SOME_SETTING=

Running:
export $(xargs < config/environments/.env)

Will set in environment:
SOME_SETTING=''

Now if you try to load this .env with Vapor the setting SOME_SETTING will not be set at all. Some configurations, e.g. RabbitMQ treat an empty string as a request to autogenerate so we must use an empty string for the setting.

The solution I propose is to detect empty string values and then set it. This change in Vapor.Provider.Dotenv would be this:

defp parse_pair([key, value], acc) do
    cond do
      String.length(key) > 0 && String.length(value) > 0 ->
        key = String.trim(key)
        value = String.trim(value)

        case starting_heredoc(value) do
          [_, delimiter] -> {key, delimiter, [], acc}
          _ -> [{key, value} | acc]
        end
      String.length(key) > 0 && String.length(value) == 0 ->
        key = String.trim(key)
        value = ""
        [{key, value} | acc]
      true ->
        acc
    end
  end

This fix is working for us.

I can generate a pull request but wanted to verify with you if this is correct?

Great project, thanks!