Custom extensions

Strawberry provides support for adding extensions. Extensions can be used to hook into different parts of the GraphQL execution and to provide additional results to the GraphQL response.

To create a custom extensions you can use extend from our Extension base class:

import strawberry
from strawberry.extensions import Extension
class MyExtension(Extension):
def get_results(self):
return {
"example": "this is an example for an extension"
}
schema = strawberry.Schema(query=Query, extensions=[MyExtension])

Hooks

Request

on_request_start and on_request_end can be used to run code when a GraphQL request starts and ends. Both methods can alternatively be implemented asynchronously.

from strawberry.extensions import Extension
class MyExtension(Extension):
def on_request_start(self):
print('GraphQL request start')
def on_request_end(self):
print('GraphQL request end')

Resolve

resolve can be used to run code before or after the execution of resolvers, this method must call _next with all the arguments, as they will be needed by the resolvers.

Note that resolve can also be implemented asynchronously.

from strawberry.types import Info
from strawberry.extensions import Extension
class MyExtension(Extension):
def resolve(self, _next, root, info: Info, *args, **kwargs):
return _next(root, info, *args, **kwargs)

Get results

get_results allows to return a dictionary of data or alternatively an awaitable resolving to a dictionary of data that will be included in the GraphQL response.

from typing import Any, Dict
from strawberry.extensions import Extension
class MyExtension(Extension):
def get_results(self) -> Dict[str, Any]:
return {}

Validation

on_validation_start and on_validation_end can be used to run code on the validation step of the GraphQL execution. Both methods can be implemented asynchronously.

from strawberry.extensions import Extension
class MyExtension(Extension):
def on_validation_start(self):
print('GraphQL validation start')
def on_validation_end(self):
print('GraphQL validation end')

Parsing

on_parsing_start and on_parsing_end can be used to run code on the parsing step of the GraphQL execution. Both methods can be implemented asynchronously.

from strawberry.extensions import Extension
class MyExtension(Extension):
def on_parsing_start(self):
print('GraphQL parsing start')
def on_parsing_end(self):
print('GraphQL parsing end')

Execution Context

The Extension object has an execution_context property on self of type ExecutionContext.

This object can be used to gain access to additional GraphQL context, or the request context. Take a look at the ExecutionContext type for available data.

from strawberry.extensions import Extension
from mydb import get_db_session
class MyExtension(Extension):
def on_request_start(self):
self.execution_context.context["db"] = get_db_session()
def on_request_end(self):
self.execution_context.context["db"].close()

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