Casing error objects

[anthonator]

Currently, when you provide a map as part of an error payload the map keys don't get cased.

For instance, when providing the following payload as part of Absinthe.Resolution's error result:

%{
  message: :unprocessable_entity,
  details: %{
    user_email: %{ validation: "required" }
  }
}

I get back the following JSON object:

{
  "message": "unprocessable_entity",
  "details": {
    "user_email": { "validation": "required" }
  }
}

Ideally, the result would be cased the same way "successful" results are. Like so:

{
  "message": "unprocessable_entity",
  "details": {
    "userEmail": { "validation": "required" }
  }
}

[anthonator]

Here's an example middleware that handles casing maps for my particular use case.

defmodule GraphQLService.Middlewares.ErrorHandler do
  @moduledoc """
  Transforms a list of validation errors into a structure that's easy for a
  client to identify and consume.

  ## Example

      %{
        message: :unprocessable_entity,
        details: %{
          user_email: %{ validation: "required" }
        }
      }
  """

  import Absinthe.Resolution

  @behaviour Absinthe.Middleware

  @doc false
  def call(%Absinthe.Resolution{ errors: [ errors ] } = resolution, _config)
    when is_list(errors)
  do
    result =
      Enum.reduce(errors, %{}, fn({ field, { _message, [ validation: validation ] } }, acc) ->
        acc
        |> Map.put(:details, Map.merge(acc[:details] || %{}, Map.put(%{}, field, %{ validation: validation })))
      end)
      |> Map.put(:message, :unprocessable_entity)
      |> to_external()

    resolution
    |> put_result({ :error, result })
  end
  def call(resolution, _config), do: resolution

  #
  # private
  #

  defp to_external(result) when is_map(result) do
    Enum.reduce(result, %{}, fn({ key, value }, acc) ->
      acc
      |> Map.put(to_external_name(key), to_external(value))
    end)
  end
  defp to_external(payload),
    do: payload

  defp to_external_name(field) do
    field
    |> to_string()
    |> Absinthe.Adapter.LanguageConventions.to_external_name(:field)
    |> String.to_atom()
  end
end

[benwilson512]

Closed by mistake :)

[benwilson512]

@bruce do you think this is a feature Absinthe should handle natively? Errors can in theory be pretty unstructured. It might be best to just have a section in the error handling documentation that shows middleware similar to the above.