From 5c3b11fdf7e5cfedffb34804345735041ba256ad Mon Sep 17 00:00:00 2001
From: David Lechner <david@pybricks.com>
Date: Sun, 28 Apr 2024 20:02:08 -0500
Subject: [PATCH] backends/service: normalize UUIDs in get_characteristic()

This fixes 4-character UUIDs causing BleakCharacteristicNotFoundError
instead of being properly resolved.

Fixes: https://github.com/hbldh/bleak/issues/1498
---
 CHANGELOG.rst             | 1 +
 bleak/backends/service.py | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 09ccb885..4b59e53a 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -29,6 +29,7 @@ Fixed
 * Fixed rare unhandled exception when scanning on macOS when using ``use_bdaddr``. Fixes #1523.
 * Fixed scanning silently failing on Windows when Bluetooth is off. Fixes #1535.
 * Fixed using wrong value for ``tx_power`` in Android backend. Fixes #1532.
+* Fixed 4-character UUIDs not working on ``BleakClient.*_gatt_char`` methods. Fixes #1498.
 
 `0.21.1`_ (2023-09-08)
 ======================
diff --git a/bleak/backends/service.py b/bleak/backends/service.py
index 63b12b3f..09c503c9 100644
--- a/bleak/backends/service.py
+++ b/bleak/backends/service.py
@@ -176,10 +176,12 @@ def get_characteristic(
         if isinstance(specifier, int):
             return self.characteristics.get(specifier)
 
+        uuid = normalize_uuid_str(str(specifier))
+
         # Assume uuid usage.
         x = list(
             filter(
-                lambda x: x.uuid == str(specifier).lower(),
+                lambda x: x.uuid == uuid,
                 self.characteristics.values(),
             )
         )