Mypy plugin and stubs for Graphene

This is basically an attempt to copy the pattern for publishing stubs + a plugin established by the sqlalchemy-stubs repo.

Installation

pip install graphene-stubs

Include the plugin in your mypy.ini file:

[mypy]
plugins = graphene_plugin

If you want to use the generic version of ObjectType then you have to call patch_object_type() at the entry point of your application, before defining any ObjectType sub-classes:

from graphene_plugin import patch_object_type
# Have to patch before defining an `ObjectType` sub-classes, OR importing any modules that define
# `ObjectType` sub-classes.
patch_object_type()


from graphene import ObjectType, Field, String, ResolveInfo


class PersonModel:
    first_name: str
    last_name: str


class AnimalModel:
    species: str


class Person(ObjectType[PersonModel]):
    first_name = Field(String, required=True)
    last_name = Field(String, required=True)

    @staticmethod
    def resolve_first_name(person: PersonModel, _: ResolveInfo) -> str:
        return person.first_name

    @staticmethod
    def resolve_last_name(person: AnimalModel, _: ResolveInfo) -> str:  # Fails, the type of `person` doesn't match the generic argument
        return person.species

Plugin Details

Because of the implementation and patterns used by Graphene, there are many cases where types are being declared and correspond to arguments used in resolvers, but it's hard for mypy to understand the correlation between them. Because of this, a plugin has been added that does nothing but throw additional errors when types don't seem to match up.

For details on exactly what the plugin supports, you can view the test data in test/test-data/unit/graphene_plugin.test, but here's a list of things currently supported:

For classes with the base class ObjectType:

• Erroring when arguments are included in a field attribute definition, but are missing in the resolver method's signature.
• Erroring when resolvers are defined that don't have corresponding field attributes.
• Erroring when the types defined in field attribute Arguments don't match up with type annotations in resolvers perfectly.
• Erroring when a resolver's return type does not match the corresponding field attribute definition
• Some amount of robustness for all of the above features, including type checking custom scalar types out of the box, following Interfaces defined in a Meta class on the ObjectType to see additional fields, typing graphene.Enum types correctly as strings, supporting both static and non-static resolver methods.

Currently not supported:

• Anything to do with Mutation classes.
• Anything to do with parsing graphql query strings passed to execute_query.

Development Setup

First, clone the repo and cd into it. Then install the repo (pip install -e .).

Then:

export MYPY_TEST_PREFIX=./test

To run the tests:

pytest -n 0 -p no:flaky

Note that "-n 0 -p no:flaky" are related to pytest plugins you may not have installed, so you may only have to run pytest.