Deprecate is_metric property of unit system (#80313)

homeassistant/util/unit_system.py

@@ -131,7 +131,13 @@ class UnitSystem:
     @property
     def is_metric(self) -> bool:
         """Determine if this is the metric unit system."""
-        return self._name == CONF_UNIT_SYSTEM_METRIC
+        report(
+            "accesses the `is_metric` property of the unit system. "
+            "This is deprecated and will stop working in Home Assistant 2023.1. "
+            "Please adjust to use instance check instead.",
+            error_if_core=False,
+        )
+        return self is METRIC_SYSTEM
 
     def temperature(self, temperature: float, from_unit: str) -> float:
         """Convert the given temperature to this unit system."""

tests/util/test_unit_system.py

@@ -296,10 +296,22 @@ def test_properties():
     assert METRIC_SYSTEM.accumulated_precipitation_unit == LENGTH_MILLIMETERS
 
 
-def test_is_metric():
+@pytest.mark.parametrize(
+    "unit_system, expected_flag",
+    [
+        (METRIC_SYSTEM, True),
+        (IMPERIAL_SYSTEM, False),
+    ],
+)
+def test_is_metric(
+    caplog: pytest.LogCaptureFixture, unit_system: UnitSystem, expected_flag: bool
+):
     """Test the is metric flag."""
-    assert METRIC_SYSTEM.is_metric
+    assert unit_system.is_metric == expected_flag
-    assert not IMPERIAL_SYSTEM.is_metric
+    assert (
+        "Detected code that accesses the `is_metric` property of the unit system."
+        in caplog.text
+    )
 
 
 @pytest.mark.parametrize(