GraphQL with Absinthe

mix caravela.gen.graphql MyApp.Domains.Library generates three files under lib/<app>_web/schema/:

library_types.ex      # Absinthe object types, with dataloader relations
library_queries.ex    # list + single-fetch per entity
library_mutations.ex  # create / update / delete + typed input objects

All three delegate to the generated context module, so the same authorization, hooks, and multi-tenant scoping you get from the REST API flow through the Absinthe resolvers too.

Dependencies

Absinthe is an optional Caravela dep. Add to your consumer app:

{:absinthe, "~> 1.7"},
{:absinthe_plug, "~> 1.5"},
{:dataloader, "~> 2.0"}

mix caravela.gen.graphql checks at runtime and prints a pointed error if any are missing.

Example output

# GENERATED: library_queries.ex
field :books, list_of(:book) do
  resolve fn _, _, resolution ->
    {:ok, Library.list_books(extract_context(resolution))}
  end
end

# GENERATED: library_mutations.ex
field :create_book, :book do
  arg :input, non_null(:book_input)

  resolve fn _, %{input: input}, resolution ->
    Library.create_book(input, extract_context(resolution))
  end
end

extract_context/1 reads %{context: ...} from the Absinthe resolution and passes it to the Caravela context. Plug your current_user/tenant into Absinthe.Plug context — everything else is automatic.

What's hidden from GraphQL

Tenant-injected fields. When the domain is multi_tenant: true, the input object omits tenant_id. Tenant id comes from the server context, not the client.

Inserted/updated timestamps. Exposed in the object type (read-only); not in input objects.

Relations

Every relation becomes a dataloader-backed field:

object :book do
  field :id, non_null(:id)
  field :title, non_null(:string)
  field :author, :author, resolve: dataloader(MyApp.Library)
end

Wire Dataloader into your Absinthe schema as usual. The Caravela generator does not emit a Dataloader source — just the resolve: reference — because the source composition depends on your Repo setup. See Absinthe's Dataloader docs.

Versioning

With version "v1", the three files move under schema/v1/ and module names become MyAppWeb.Schema.V1.LibraryTypes etc. The Absinthe schema you stitch together in lib/<app>_web/schema.ex imports the types/queries/mutations per version — keep /graphql/v1 and /graphql/v2 endpoints separate in your router.