Event field types include None but (maybe) shouldn't #1298
Description
With the new 4.2.0 release that adds the py.typed marker, mypy is reporting that my Event handling code should be ready for None values. For instance,
if isinstance(event, h2.events.RequestReceived):
stream = HTTP2StreamHandler(
self._state,
event.stream_id, # mypy: incompatible type "int | None"; expected "int"
event.headers, # mypy: incompatible type "list[HeaderTuple] | None"; expected "Iterable[HeaderTuple]"
)I can expect these fields to always be set, right? I could add assert statements like this:
if isinstance(event, h2.events.RequestReceived):
assert event.stream_id is not None
assert event.headers is not None
stream = HTTP2StreamHandler(
self._state,
event.stream_id,
event.headers,
)But it's clunky to make users do this.
I see that Event objects are constructed incrementally, so their fields can be None temporarily in h2 code, but I wish the types could reflect what I should expect as a user. What would you think of something like this?
class RequestReceived(Event):
stream_id: int
headers: list[HeaderTuple]
def __init__(self) -> None:
self.stream_ended: StreamEnded | None = None
self.priority_updated: PriorityUpdated | None = NoneIt would work as long as h2 itself does not access stream_id / headers before setting them.