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ObservableDeferred: run observers in order (#11229)

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Richard van der Hoff 2021-11-02 00:17:35 +00:00 • committed by GitHub
parent 93aa670642
commit 46d0937447
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4 changed files with 88 additions and 20 deletions
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34
synapse/util/async_helpers.py
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@ -22,11 +22,11 @@ from typing import (
Any,
Awaitable,
Callable,
Collection,
Dict,
Generic,
Hashable,
Iterable,
List,
Optional,
Set,
TypeVar,
@ -76,12 +76,17 @@ class ObservableDeferred(Generic[_T]):
def __init__(self, deferred: "defer.Deferred[_T]", consumeErrors: bool = False):
object.__setattr__(self, "_deferred", deferred)
object.__setattr__(self, "_result", None)
object.__setattr__(self, "_observers", set())
object.__setattr__(self, "_observers", [])
def callback(r):
object.__setattr__(self, "_result", (True, r))
while self._observers:
observer = self._observers.pop()
# once we have set _result, no more entries will be added to _observers,
# so it's safe to replace it with the empty tuple.
observers = self._observers
object.__setattr__(self, "_observers", ())
for observer in observers:
try:
observer.callback(r)
except Exception as e:
@ -95,12 +100,16 @@ class ObservableDeferred(Generic[_T]):
def errback(f):
object.__setattr__(self, "_result", (False, f))
while self._observers:
# once we have set _result, no more entries will be added to _observers,
# so it's safe to replace it with the empty tuple.
observers = self._observers
object.__setattr__(self, "_observers", ())
for observer in observers:
# This is a little bit of magic to correctly propagate stack
# traces when we `await` on one of the observer deferreds.
f.value.__failure__ = f
observer = self._observers.pop()
try:
observer.errback(f)
except Exception as e:
@ -127,20 +136,13 @@ class ObservableDeferred(Generic[_T]):
"""
if not self._result:
d: "defer.Deferred[_T]" = defer.Deferred()
def remove(r):
self._observers.discard(d)
return r
d.addBoth(remove)
self._observers.add(d)
self._observers.append(d)
return d
else:
success, res = self._result
return defer.succeed(res) if success else defer.fail(res)
def observers(self) -> "List[defer.Deferred[_T]]":
def observers(self) -> "Collection[defer.Deferred[_T]]":
return self._observers
def has_called(self) -> bool: