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 four 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.Underscore, which is similar to the Absinthe.Adapter.LanguageConventions adapter but converts all incoming identifiers to underscores and does not modify outgoing identifiers (since those are already expected to be underscores). Unlike Absinthe.Adapter.Passthrough this does not break introspection.
• 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).
• Absinthe.Adapter.StrictLanguageConventions, which expects schemas to be defined in snake_case, translating to camelCase for outgoing results. This adapter requires incoming query documents to use camelCase.

To set an adapter, you pass a configuration option at runtime:

For Absinthe.run/3:

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

For Absinthe.Plug:

forward "/api",
  to: Absinthe.Plug,
  init_opts: [schema: MyAppWeb.Schema, adapter: YourApp.Adapter.TheAdapterName]

For GraphiQL:

forward "/graphiql",
  to: Absinthe.Plug.GraphiQL,
  init_opts: [schema: MyAppWeb.Schema, adapter: YourApp.Adapter.TheAdapterName]

Check Absinthe.Plug for full documentation on using the Plugs

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.