Code Using GraphQL

# schema.gql
"""
A supernatural being considered divine and sacred
"""
type Deity {
  name: String!
  power: String @deprecated(reason: "no more supported")
}
type Query {
  deity(name: String! = "Morpheus"): Deity!
}

{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
module API (api) where
import Data.ByteString.Lazy.Char8 (ByteString)
import Data.Morpheus (interpreter)
import Data.Morpheus.Document (importGQLDocument)
import Data.Morpheus.Types (RootResolver (..), Undefined (..))
import Data.Text (Text)
importGQLDocument "schema.gql"
rootResolver :: RootResolver IO () Query Undefined Undefined
rootResolver =
  RootResolver
    { queryResolver = Query {deity},
      mutationResolver = Undefined,
      subscriptionResolver = Undefined
    }
  where
    deity DeityArgs {name} =
      pure
        Deity
          { name = pure name,
            power = pure (Just "Shapeshifting")
          }
api :: ByteString -> IO ByteString
api = interpreter rootResolver

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PartialTypeSignatures #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
 
-- imports omitted for brevity...
 
graphql "Library" "library.graphql" -- all the magic happens here! 🪄🎩
 
-- ... a bit more code...
 
libraryServer :: SqlBackend -> ServerT ObjectMapping i Library ServerErrorIO _
libraryServer conn =
  resolver
    ( object @"Book"
        ( field @"id" bookId,
          field @"title" bookTitle,
          field @"author" bookAuthor,
          field @"imageUrl" bookImage
        ),
      object @"Author"
        ( field @"id" authorId,
          field @"name" authorName,
          field @"books" authorBooks
        ),
      object @"Query"
        ( method @"authors" allAuthors,
          method @"books" allBooks
        ),
      object @"Mutation"
        ( method @"newAuthor" newAuthor,
          method @"newBook" newBook
        ),
      object @"Subscription"
        (method @"allBooks" allBooksConduit)
    )
  where
    bookId :: Entity Book -> ServerErrorIO Integer
    bookId (Entity (BookKey k) _) = pure $ toInteger k
    -- ... more resolvers...