An Elixir implementation of Facebook's GraphQL.
This is the core GraphQL query parsing and execution engine whose goal is to be transport, server and datastore agnostic.
In order to setup an HTTP server (ie Phoenix) to handle GraphQL queries you will need plug_graphql. Examples for Phoenix can be found at hello_graphql_phoenix, so look here for a starting point for writing your own schemas.
Other ways of handling queries will be added in due course.
First, add GraphQL to your mix.exs dependencies:
defp deps do
[{:graphql, "~> 0.3"}]
endAdd GraphQL to your mix.exs applications:
def application do
# Add the application to your list of applications.
# This will ensure that it will be included in a release.
[applications: [:logger, :graphql]]
endThen, update your dependencies:
$ mix deps.getFirst setup your schema
defmodule TestSchema do
def schema do
%GraphQL.Schema{
query: %GraphQL.Type.ObjectType{
name: "RootQueryType",
fields: %{
greeting: %{
type: %GraphQL.Type.String{},
resolve: &TestSchema.greeting/3,
description: "Greeting",
args: %{
name: %{type: %GraphQL.Type.String{}, description: "The name of who you'd like to greet."},
}
}
}
}
}
end
def greeting(_, %{name: name}, _), do: "Hello, #{name}!"
def greeting(_, _, _), do: "Hello, world!"
endExecute a simple GraphQL query
iex> GraphQL.execute(TestSchema.schema, "{greeting}")
{:ok, %{data: %{"greeting" => "Hello, world!"}}}This is a work in progress, right now here's what is done:
- Parser for GraphQL (including Type definitions)
- AST matching the
graphql-jstypes as closely as possible - Schema definition
- Query execution
- Scalar types
- Arguments
- Multiple forms of resolution
- Complex types (List, Object, etc)
- Fragments in queries
- Extract variable values
- Introspection
- [WIP] Query validation
- Directives
- GraphQL Spec This incredibly well written spec made writing the GraphQL parser pretty straightforward.
- GraphQL JS Reference Implementation
Tokenisation is done with leex and parsing with yecc. Both very useful Erlang tools for parsing. Yecc in particular is used by Elixir itself.
Some resources on using leex and yecc:
- http://relops.com/blog/2014/01/13/leex_and_yecc/
- http://andrealeopardi.com/posts/tokenizing-and-parsing-in-elixir-using-leex-and-yecc/
The Execution logic follows the GraphQL JS Reference Implementation pretty closely, as does the module structure of the project. Not to mention the naming of files and concepts.
If you spot anything that isn't following Elixir conventions though, that's a mistake. Please let us know by opening an issue or a PR and we'll fix it.
Clone the repo and fetch its dependencies:
$ git clone https://github.com/graphql-elixir/graphql.git
$ cd graphql
$ mix deps.get
$ mix test
Using the
language-erlangpackage?.xrland.yrlfiles not syntax highlighting?
Syntax highlighting in Atom for leex (.xrl) and yecc (yrl) can be added by modifying grammars/erlang.cson.
Just open the atom-language-erlang package code in Atom and make the change described here:
jonathanmarvens/atom-language-erlang#11
however if that PR has been merged then just grab the latest version of the plugin!
We actively welcome pull requests, bug reports, feedback, issues, questions. Come and chat in the #erlang channel on Slack
If you're planning to implement anything major, please let us know before you get too far so we can make sure your PR will be as mergable as possible. Oh, and don't forget to write tests.
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