Duplicate fields on type are currently allowed

[kdawgwilk]

Environment

• Elixir version (elixir -v): 1.12.3
• Absinthe version (mix deps | grep absinthe): 1.6.6
• Client Framework and version (Relay, Apollo, etc): N/A

Expected behavior

Absinthe fails to compile my schema and gives an error message indicating that the same field is being defined more than once on a type

Actual behavior

schema compiles without issue

Relevant Schema/Middleware Code

defmodule MySchema do
  use Absinthe.Schema

  query do
    field :foo, :string
    field :foo, :string
  end
end

This results in a malformed SDL file generated from the mix absinthe.schema.sdl task which is rejected by most tooling e.g. schema registries.

[kdawgwilk]

This can commonly occur when sharing schema types between multiple graphs when using import_types and import_fields