subscriptions not calling source

[korzi27]

Hello there,

very similar to Issue 320 I experienced errors in my productive app that subscriptions are not calling the source definition. Going back to the documentary example i experience the same problem:

import asyncio
from ariadne import SubscriptionType, make_executable_schema
from ariadne.asgi import GraphQL
from ariadne.asgi.handlers import GraphQLWSHandler


type_def = """
    type Query {
        _unused: Boolean
    }

    type Subscription {
        counter: Int!
    }
"""

subscription = SubscriptionType()

@subscription.source("counter")
async def counter_generator(obj, info):
    print('Source')
    for i in range(5):
        await asyncio.sleep(1)
        yield i


@subscription.field("counter")
def counter_resolver(count, info):
    print('field')
    return count + 1


schema = make_executable_schema(type_def, subscription)
app = GraphQL(schema, debug=True, websocket_handler = GraphQLWSHandler())

Calling with uvicorn app:app

Now i am trying to call the subsricptions with

import asyncio
import httpx

async def graphql_subscription(endpoint, subscription_query):
    async with httpx.AsyncClient() as client:
        response = await client.post(endpoint, json={'query': subscription_query})
        print(response.json())
        data = response.json()
        print(data)


graphql_endpoint = 'http://localhost:8000/graphql/'
subscription_query = '''subscription MySubscri{
                        counter}'''


asyncio.run(graphql_subscription(graphql_endpoint, subscription_query))

Ending up with the error message unsupported operand type(s) for +: 'NoneType' and 'int' as count+1 cannot be computed as count is None as the source is never called.

python 3.10.5, ariadne 0.22, httpx 0.22.6, uvicorn 0.27.1

Help is pretty much appreciated.

[rafalp]

client.post

Subscriptions should only work with websockets, so fact that even subscription's resolver is called is a bug in Ariadne.

[rafalp]

We'll fix this in Ariadne 0.23 so trying to do a subscription without using a WebSocket will return an error.

For posterity what happened here is there are two query execution strategies in GraphQL: execute and subscribe. execute just calls resolvers in a cascade. subscribe calls sources and whenever a source yields a result, calls its resolver.

subscribe is only used for connections made over the websocket. What happened there is execute was called against Subscription fields resolvers like it would be against Query or Mutation and getting error.