diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index f61396bb79..298809742a 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -28,11 +28,11 @@ from typing import (
Type,
TypeVar,
Union,
- cast,
)
from prometheus_client import Metric
from prometheus_client.core import REGISTRY, Counter, Gauge
+from typing_extensions import ParamSpec
from twisted.internet import defer
@@ -256,24 +256,48 @@ def run_as_background_process(
return defer.ensureDeferred(run())
-F = TypeVar("F", bound=Callable[..., Awaitable[Optional[Any]]])
+P = ParamSpec("P")
-def wrap_as_background_process(desc: str) -> Callable[[F], F]:
- """Decorator that wraps a function that gets called as a background
- process.
+def wrap_as_background_process(
+ desc: str,
+) -> Callable[
+ [Callable[P, Awaitable[Optional[R]]]],
+ Callable[P, "defer.Deferred[Optional[R]]"],
+]:
+ """Decorator that wraps an asynchronous function `func`, returning a synchronous
+ decorated function. Calling the decorated version runs `func` as a background
+ process, forwarding all arguments verbatim.
+
+ That is,
+
+ @wrap_as_background_process
+ def func(*args): ...
+ func(1, 2, third=3)
+
+ is equivalent to:
+
+ def func(*args): ...
+ run_as_background_process(func, 1, 2, third=3)
- Equivalent to calling the function with `run_as_background_process`
+ The former can be convenient if `func` needs to be run as a background process in
+ multiple places.
"""
- def wrap_as_background_process_inner(func: F) -> F:
+ def wrap_as_background_process_inner(
+ func: Callable[P, Awaitable[Optional[R]]]
+ ) -> Callable[P, "defer.Deferred[Optional[R]]"]:
@wraps(func)
def wrap_as_background_process_inner_2(
- *args: Any, **kwargs: Any
+ *args: P.args, **kwargs: P.kwargs
) -> "defer.Deferred[Optional[R]]":
- return run_as_background_process(desc, func, *args, **kwargs)
+ # type-ignore: mypy is confusing kwargs with the bg_start_span kwarg.
+ # Argument 4 to "run_as_background_process" has incompatible type
+ # "**P.kwargs"; expected "bool"
+ # See https://github.com/python/mypy/issues/8862
+ return run_as_background_process(desc, func, *args, **kwargs) # type: ignore[arg-type]
- return cast(F, wrap_as_background_process_inner_2)
+ return wrap_as_background_process_inner_2
return wrap_as_background_process_inner
|
