MaskErrors does not mask errors for subscriptions

[axiomofjoy]

The MaskErrors schema extension does not seem to mask errors for subscriptions. I am running on the latest version of strawberry. Example included below:

from typing import AsyncIterator
import strawberry
from strawberry.extensions import MaskErrors


@strawberry.type
class Query:
    @strawberry.field
    def hello(self) -> str:
        raise Exception("boom")
        return "world"


@strawberry.type
class Subscription:
    @strawberry.subscription
    async def stream(self) -> AsyncIterator[str]:
        yield "hello"
        yield "world"
        raise Exception("boom")


schema = strawberry.Schema(
    query=Query, subscription=Subscription, extensions=[MaskErrors()]
)

The errors are masked for queries:

But not for subscriptions:

Describe the Bug

I expect the MaskErrors extension to mask my errors for subscriptions as well as queries and mutations, but it does not appear to do so.

System Information

• Operating system: MacOS
• Strawberry version (if applicable): 0.247.0

Upvote & Fund

• We're using Polar.sh so you can upvote and help fund this issue.
• We receive the funding once the issue is completed & confirmed by you.
• Thank you in advance for helping prioritize & fund our backlog.

[Speedy1991]

Can confirm this - the problem is, a subscriptions never sets an execution_context.result (it is always None) and therefore the error check failes.

I think the problem is send_next because it just formats the error and in line 381 it send the message without going through the gql middlewares

Same problem in the graphql-ws implementation here