ExAws.Config.build_base() cannot get region when using configparser_ex

[carloshanson-itrac]

I would like to use {:awscli, profile, timeout} for all AWS config values.

config :ex_aws,
  access_key_id: [{:system, "AWS_ACCESS_KEY_ID"}, {:awscli, "profile", 30}],
  secret_access_key: [{:system, "AWS_SECRET_ACCESS_KEY"}, {:awscli, "profile", 30}],
  region: [{:system, "AWS_REGION"}, {:awscli, "profile", 30}]

However, when using this method, I receive the following error:

iex(1)> ExAws.S3.list_objects("bucket-name") |> ExAws.request()
** (FunctionClauseError) no function clause matching in Regex.run/3    
    
    The following arguments were given to Regex.run/3:
    
        # 1
        ~r/^(us|eu|af|ap|sa|ca|me)\-\w+-\d?-?\w+$/
    
        # 2
        %{
          access_key_id: "ABCDEF...",
          secret_access_key: "abc123...",
          region: "us-west-2"
        }
    
        # 3
        []
    
    Attempted function clauses (showing 1 out of 1):
    
        def run(%Regex{} = regex, string, options) when is_binary(string)
    
    (elixir 1.18.4) lib/regex.ex:360: Regex.run/3
    (elixir 1.18.4) lib/enum.ex:4404: Enum.find_list/3
    (ex_aws 2.5.10) lib/ex_aws/config/defaults.ex:115: ExAws.Config.Defaults.host/2
    (ex_aws 2.5.10) lib/ex_aws/config/defaults.ex:110: ExAws.Config.Defaults.get/2
    (ex_aws 2.5.10) lib/ex_aws/config.ex:96: ExAws.Config.build_base/2
    (ex_aws 2.5.10) lib/ex_aws/config.ex:69: ExAws.Config.new/2
    (ex_aws 2.5.10) lib/ex_aws.ex:73: ExAws.request/2
    iex:1: (file)

Argument "# 2" above should be "us-west-2".

The problem is in ExAws.Config.build_base() when it tries to set region. The last function in the pipeline, ExAws.Config.retrieve_runtime_value(), can return a single value or a map.

region =
      (Map.get(overrides, :region) ||
         Map.get(service_config, :region) ||
         Map.get(common_config, :region) ||
         "us-east-1")
      |> retrieve_runtime_value(%{})

In the case of {:system, "AWS_REGION"}, it returns a single value, e.g. "us-east-1". When using :awscli, however, it returns the map seen in argument "# 2" above.

One solution would be to adjust the pipeline in ExAws.Config.build_base() to get the region from a map if that is what is returned or accept the single returned value.

Alternately, maybe we should specify and use the :awscli key, for example, {:awscli, "profile", 30, "region"}, so it can be pulled from the map that ExAws.Config.AuthCache.get() returns. We specify the environment variable name when using :system, so I'm unclear why we don't do that for :awscli too.

While there is no example in the documentation about using :awscli for region, it seems like it should be an option.

Thanks.