[Enum] Default value not interpreted properly in case of keyword list

[jonatanklosko]

Given the following enum definition

enum :project_order_by do
  value :inserted_at_asc, as: [asc: :inserted_at]
  value :inserted_at_desc, as: [desc: :inserted_at]
end

and the following field with a default enum argument

field :projects, list_of(:project) do
  arg :order_by, non_null(:project_order_by), default_value: [asc: :inserted_at]
  resolve &Resolvers.Projects.list_projects/3
end

I get the following error

The default_value for an enum must be present in the enum values.

Could not use default value of `[asc: :inserted_at]` for :project_order_by.

Valid values are:

 * [desc: :inserted_at]
 * [asc: :inserted_at]

Reason

absinthe/lib/absinthe/phase/schema/validation/default_enum_value_present.ex

Lines 37 to 38 in 00601ff

	List.wrap(default_value)
	|> Enum.all?(fn default -> default in values end)

The above call to List.wrap does nothing in case of [asc: :inserted_at], but then it uses Enum.all? and ends up checking if {:asc, :inserted_at} belongs to values instead of [asc: :inserted_at].

What is the reasoning behind using List.wrap?
Edit: it was introduced in #762 to handle default value for list_of(enum).

Environment

• Elixir version (elixir -v): Elixir 1.9.1 (compiled with Erlang/OTP 22)
• Absinthe version (mix deps | grep absinthe): 1.5.1