Maple

WARNING: This release is just for posterity. There is a major rewrite coming.

Maple is an automatic, compile time, client code generator for GraphQL schemas. At best it creates easy to use API functions for use in your code. At worst it can be used as a CLI for a GraphQL API.

Best illustrated by an example - given the following code

defmodule Maple.Examples.Github.Config do
  Application.put_env(:maple, :api_url, "https://api.github.com/graphql")
  Application.put_env(:maple, :additional_headers, %{"Authorization" => "Bearer TOKEN"})
end

defmodule Maple.Examples.Github do
  use Maple
end

`` will create all the query and mutation functions for the GitHub GraphQL API.

So you can do the following:

iex(1)> c "examples/github.ex", "." # We need to compile the BEAM file to access the documentation
[Maple.Examples.Github, Maple.Examples.Github.Config]

iex(2)> h Maple.Examples.Github.user

                            def user(params, fields)

Lookup a user by login.

Param name: login

  • Description: The user's login.
  • Type: String
  • Required: Yes

iex(3)> Maple.Examples.Github.viewer("login")
%Maple.Response{body: %{"viewer" => %{"login" => "maxneuvians"}}, status: 200}

iex(4)> Maple.Examples.Github.user(%{login: "maxneuvians"}, "name")
%Maple.Response{body: %{"user" => %{"name" => "Max Neuvians"}}, status: 200}

iex(5)> Maple.Examples.Github.user(%{},"name")
{:error, "Query is missing the following required params: login"}

query functions can are either arity /1 or /2 depending if they have required params. mutation functions are always arity /2. Arity /2 functions always take a map as the first argument and a string as the second, which match the GraphQL params and fields concept.

Function names are changed from camel to snake case. ex listUsers becomes list_users.

Take a look at examples/ for more examples.

Subscriptions

It appears that at this point in time the support of subscriptions over web sockets are a work in progress.

For example, https://github.com/apollographql/subscriptions-transport-ws/ implements a legacy (graphql-subscriptions) and a current (graphql-ws) web socket subprotocol for Apollo servers. For more information please take a look here: https://github.com/apollographql/subscriptions-transport-ws/blob/master/PROTOCOL.md

Once Absinthe 1.4 has been released I will implement it as an adapter. Here is an example interaction with a Scaphold.io API:

iex(1)> Maple.Examples.Scaphold.subscribe_to_post(%{mutations: ["createPost"]}, "mutation value {id content title}", &Maple.Examples.Scaphold.result/1)

18:40:22.932 [info]  Connected!
:ok
18:40:23.432 [info]  Successful subscription

iex(2)> Maple.Examples.Scaphold.create_post(%{input: %{title: "Hello", content: "World"}},"id")

18:45:24.977 [info]  Received subscription data
%{"data" => %{"subscribeToPost" => %{"mutation" => "createPost",
    "value" => %{"content" => "World", "id" => "UG9zdDoxOA==",
      "title" => "Hello"}}}}

%Maple.Response{body: %{"createPost" => %{"changedPost" => %{"id" => "UG9zdDoxOA=="}}},
status

Options

The module takes a options from the configuration:

config :maple,
  build_type_structs: false,
  http_adapter: Maple.Clients.Http,
  websocket_adapter: Maple.Clients.WebsocketApollo

• :build_type_structs - Default is false. If set to true the macro will create structs for all the fields found in the introspection query. All types are namespaced into Maple.Types.

• :http_adapter - The default HTTP adapter for completing transactions against the GraphQL server. Default is: Maple.Clients.Http

• :websocket_adapter - The default Websocket adapter for completing transactions against the GraphQL server using websockets. Default is: Maple.Clients.WebsocketApollo

Installation

def deps do
  [{:maple, git: "https://github.com/maxneuvians/maple"}]
end

or

def deps do
  [{:maple, "~> 0.5.0"}]
end

Configuration

If you only access one GraphQL API you just need to add the following to you config.exs

config :maple,
  build_type_structs: false,
  http_adapter: Maple.Clients.Http,
  websocket_adapter: Maple.Clients.WebsocketApollo,
  api_url: "URL",
  wss_url:, "WSS_URL", # If you are using subscriptions over websockets.
  additional_headers: %{"Authorization": "Bearer TOKEN"} # If you have any additional headers

Ramblings

This library is in development.

Contributions and issues welcome!

Also if you think this is a terrible idea, please let me know!

ToDo

• Refactor macro code
• Add proper documentation
• Support subscriptions
• Support fragments
• Look into validation through structs
• Alternative syntax for fields
• Expand help with required attributes
• Expand help with attribute descriptions

License

MIT

Version

0.5.0