Freight

Freight is a library for Absinthe GraphQL that helps you build mutation payload results. Inspired by the GraphQL APIs of GitHub and Shopify, who also aim to keep syntactical GraphQL errors, like missing fields and malformed queries, seperate from validation and other business logic errors.

It is heavily inspired by Kronky, I decided to build my own library because I did not like how much it is focussed on ecto changesets, and missed customisability that was required for a project I work on.

Configuration

You can set a custom error object that will be returned in the errors array in your payloads. This object must be defined in the schema you're calling define_payload from.

config :freight,
  error_object: :user_error
  # whenever a field is snake-cased (like an ecto field for example), setting this to `true` will camelize it like Absinthe would
  lower_camelize_field_name: true

Usage

Below is a documented example of how to define Freight payloads in your schema

defmodule FreightDemo.Schema.Example do
  use Absinthe.Schema.Notation

  import Freight.Payload

  object :user do
    field(:name, :string)
  end

  object :comment do
    field(:body, :string)
    field(:author, :user)
  end

  define_payload(:create_comment_payload, author: :user, comment: :comment)

  field :create_comment, type: :create_comment_payload do
    arg(:body, non_null(:string))

    resolve(&FreightDemo.Resolver.create_comment/3)
    middleware(&build_payload/2)
  end
end

Returning errors works just like in Absinthe

defmodule FreightDemo.Resolver do
  def create_comment(_parent, %{body: body}, _context) do
    # your logic

    {:ok, author: %{}, comment: %{}}
  end

  # OR

  def create_comment(_parent, %{body: body}, _context) do
    # your logic

    {:error, "Something went horribly wrong!"}
  end
end

More extensive documentation on defining errors can be found in the documentation

Installation

Add the following to your mix.exs file

def deps do
  [
    {:freight, "~> 0.4.0"}
  ]
end

Documentation can be found at https://hexdocs.pm/freight.