GraphQL-core-next

GraphQL-core-next is a Python port of GraphQL.js, the JavaScript reference implementation for GraphQL, a query language for APIs created by Facebook.

The current version 1.0.0rc2 of GraphQL-core-next is up-to-date with GraphQL.js version 14.0.0rc2. All parts of the API are covered by an extensive test suite of currently 1529 unit tests.

Documentation

A more detailed documentation for GraphQL-core-next can be found at graphql-core-next.readthedocs.io.

There will be also blog articles with more usage examples.

Getting started

An overview of GraphQL in general is available in the README for the Specification for GraphQL. That overview describes a simple set of GraphQL examples that exist as tests in this repository. A good way to get started with this repository is to walk through that README and the corresponding tests in parallel.

Installation

GraphQL-core-next can be installed from PyPI using the built-in pip command:

python -m pip install graphql-core-next

Alternatively, you can also use pipenv for installation in a virtual environment:

pipenv install graphql-core-next

Usage

GraphQL-core-next provides two important capabilities: building a type schema, and serving queries against that type schema.

First, build a GraphQL type schema which maps to your code base:

from graphql import (
    GraphQLSchema, GraphQLObjectType, GraphQLField, GraphQLString)

schema = GraphQLSchema(
    query=GraphQLObjectType(
        name='RootQueryType',
        fields={
            'hello': GraphQLField(
                GraphQLString,
                resolve=lambda obj, info: 'world')
        }))

This defines a simple schema with one type and one field, that resolves to a fixed value. The resolve function can return a value, a co-routine object or a list of these. It takes two positional arguments; the first one provides the root or the resolved parent field, the second one provides a GraphQLResolveInfo object which contains information about the execution state of the query, including a context attribute holding per-request state such as authentication information or database session. Any GraphQL arguments are passed to the resolve functions as individual keyword arguments.

Note that the signature of the resolver functions is a bit different in GraphQL.js, where the context is passed separately and arguments are passed as a single object. Also note that GraphQL fields must be passed as a GraphQLField object explicitly. Similarly, GraphQL arguments must be passed as GraphQLArgument objects.

A more complex example is included in the top level tests directory.

Then, serve the result of a query against that type schema.

from graphql import graphql_sync

query = '{ hello }'

print(graphql_sync(schema, query))

This runs a query fetching the one field defined, and then prints the result:

ExecutionResult(data={'hello': 'world'}, errors=None)

The graphql_sync function will first ensure the query is syntactically and semantically valid before executing it, reporting errors otherwise.

from graphql import graphql_sync

query = '{ boyhowdy }'

print(graphql_sync(schema, query))

Because we queried a non-existing field, we will get the following result:

ExecutionResult(data=None, errors=[GraphQLError(
    "Cannot query field 'boyhowdy' on type 'RootQueryType'.",
    locations=[SourceLocation(line=1, column=3)])])

The graphql_sync function assumes that all resolvers return values synchronously. By using coroutines as resolvers, you can also create results in an asynchronous fashion with the graphql function.

import asyncio
from graphql import (
    graphql, GraphQLSchema, GraphQLObjectType, GraphQLField, GraphQLString)


async def resolve_hello(obj, info):
    await asyncio.sleep(3)
    return 'world'

schema = GraphQLSchema(
    query=GraphQLObjectType(
        name='RootQueryType',
        fields={
            'hello': GraphQLField(
                GraphQLString,
                resolve=resolve_hello)
        }))


async def main():
    query = '{ hello }'
    print('Fetching the result...')
    result = await graphql(schema, query)
    print(result)


loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(main())
finally:
    loop.close()

Goals and restrictions

GraphQL-core-next tries to reproduce the code of the reference implementation GraphQL.js in Python as closely as possible and to stay up-to-date with the latest development of GraphQL.js.

It has been created as an alternative to GraphQL-core, a prior work by Syrus Akbary, which was based on an older version of GraphQL.js and targeted older Python versions. Some parts of the code base of GraphQL.js have been inspired by GraphQL-core or directly taken over with only slight modifications, but most of the code base has been re-implemented from scratch, replicating the latest code in GraphQL.js and adding type hints. Recently, GraphQL-core has also been modernized, but its focus is primarily to serve as as a solid base library for Graphene, a more high-level framework for building GraphQL APIs in Python.

Design goals for the GraphQL-core-next library are:

• to be a simple, cruft-free, state-of-the-art implementation of GraphQL using current library and language versions
• to be very close to the GraphQL.js reference implementation, while still using a Pythonic API and code style
• making use of Python type hints, similar to how GraphQL.js makes use of Flow
• replicate the complete Mocha-based test suite of GraphQL.js using pytest

Some restrictions (mostly in line with the design goals):

• requires Python >= 3.6
• does not support a few deprecated methods and options of GraphQL.js
• supports asynchronous operations only via async.io
• does not support additional executors and middleware like GraphQL-core
• the benchmarks have not yet been ported to Python

Changelog

Changes are tracked as GitHub releases.

Credits

The GraphQL-core-next library

• has been created and is maintained by Christoph Zwerschke
• uses ideas and code from GraphQL-core, a prior work by Syrus Akbary
• is a Python port of GraphQL.js which has been created and is maintained by Facebook, Inc.

License

GraphQL-core-next is MIT-licensed.