From 41818cda1fcb086fc41cab7b60da46954ec1dd4a Mon Sep 17 00:00:00 2001
From: reivilibre <oliverw@matrix.org>
Date: Wed, 2 Feb 2022 16:51:00 +0000
Subject: [PATCH] Fix type errors introduced by new annotations in the
 Prometheus Client library. (#11832)

Co-authored-by: David Robertson <davidr@element.io>
---
 changelog.d/11832.misc         |  1 +
 synapse/metrics/__init__.py    | 10 +++++++++-
 synapse/python_dependencies.py |  3 +--
 3 files changed, 11 insertions(+), 3 deletions(-)
 create mode 100644 changelog.d/11832.misc

diff --git a/changelog.d/11832.misc b/changelog.d/11832.misc
new file mode 100644
index 000000000..5ff117d93
--- /dev/null
+++ b/changelog.d/11832.misc
@@ -0,0 +1 @@
+Fix type errors introduced by new annotations in the Prometheus Client library.
\ No newline at end of file
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index 9e6c1b2f3..cca084c18 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -30,6 +30,7 @@ from typing import (
     Type,
     TypeVar,
     Union,
+    cast,
 )
 
 import attr
@@ -60,7 +61,7 @@ all_gauges: "Dict[str, Union[LaterGauge, InFlightGauge]]" = {}
 HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
 
 
-class RegistryProxy:
+class _RegistryProxy:
     @staticmethod
     def collect() -> Iterable[Metric]:
         for metric in REGISTRY.collect():
@@ -68,6 +69,13 @@ class RegistryProxy:
                 yield metric
 
 
+# A little bit nasty, but collect() above is static so a Protocol doesn't work.
+# _RegistryProxy matches the signature of a CollectorRegistry instance enough
+# for it to be usable in the contexts in which we use it.
+# TODO Do something nicer about this.
+RegistryProxy = cast(CollectorRegistry, _RegistryProxy)
+
+
 @attr.s(slots=True, hash=True, auto_attribs=True)
 class LaterGauge:
 
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 80786464c..22b4606ae 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -76,8 +76,7 @@ REQUIREMENTS = [
     "msgpack>=0.5.2",
     "phonenumbers>=8.2.0",
     # we use GaugeHistogramMetric, which was added in prom-client 0.4.0.
-    # 0.13.0 has an incorrect type annotation, see #11832.
-    "prometheus_client>=0.4.0,<0.13.0",
+    "prometheus_client>=0.4.0",
     # we use `order`, which arrived in attrs 19.2.0.
     # Note: 21.1.0 broke `/sync`, see #9936
     "attrs>=19.2.0,!=21.1.0",