Guard invalid data sensor significant change (#74369)

homeassistant/components/sensor/significant_change.py

@@ -63,13 +63,23 @@ def async_check_significant_change(
         absolute_change = 1.0
         percentage_change = 2.0
 
+    try:
+        # New state is invalid, don't report it
+        new_state_f = float(new_state)
+    except ValueError:
+        return False
+
+    try:
+        # Old state was invalid, we should report again
+        old_state_f = float(old_state)
+    except ValueError:
+        return True
+
     if absolute_change is not None and percentage_change is not None:
         return _absolute_and_relative_change(
-            float(old_state), float(new_state), absolute_change, percentage_change
+            old_state_f, new_state_f, absolute_change, percentage_change
         )
     if absolute_change is not None:
-        return check_absolute_change(
-            float(old_state), float(new_state), absolute_change
-        )
+        return check_absolute_change(old_state_f, new_state_f, absolute_change)
 
     return None

tests/components/sensor/test_significant_change.py

@@ -52,6 +52,8 @@ TEMP_FREEDOM_ATTRS = {
         ("12.1", "12.2", TEMP_CELSIUS_ATTRS, False),
         ("70", "71", TEMP_FREEDOM_ATTRS, True),
         ("70", "70.5", TEMP_FREEDOM_ATTRS, False),
+        ("fail", "70", TEMP_FREEDOM_ATTRS, True),
+        ("70", "fail", TEMP_FREEDOM_ATTRS, False),
     ],
 )
 async def test_significant_change_temperature(old_state, new_state, attrs, result):