Absinthe supports an adapter mechanism that allows developers to define their schema using one code convention (eg, snake_cased fields and arguments), but accept query documents and return results (including names in errors) in another (eg, camelCase).

Adapters aren’t a part of GraphQL, but a utility that Absinthe adds so that both client and server can use use conventions most natural to them.

Absinthe ships with two adapters:

• Absinthe.Adapter.LanguageConventions, which expects schemas to be defined in snake_case (the standard Elixir convention), translating to/from camelCase for incoming query documents and outgoing results. (This is the default as of v0.3.)
• Absinthe.Adapter.Passthrough, which is a no-op adapter and makes no modifications. (Note at the current time this does not support introspection if you’re using camelized conventions).

To set an adapter, you can set an application configuration value:

config :absinthe,
  adapter: YourApp.Adapter.TheAdapterName

Or, you can provide it as an option to Absinthe.run/3:

Absinthe.run(
  query,
  MyApp.Schema,
  adapter: YourApp.Adapter.TheAdapterName
)

Notably, this means you’re able to switch adapters on case-by-case basis. In a Phoenix application, this means you could even support using different adapters for different clients.

A custom adapter module must merely implement the Absinthe.Adapter protocol, in many cases with use Absinthe.Adapter and only overriding the desired functions.

Writing Your Own

All you may need to implement in your adapter is to_internal_name/2 and to_external_name/2.

Check out Absinthe.Adapter.LanguageConventions for a good example.

Note that types that are defined external to your application (including the introspection types) may not be compatible if you’re using a different adapter.