From bb42eb11761176964ee1533256ac219896475f6d Mon Sep 17 00:00:00 2001
From: Erik Montnemery <erik@montnemery.com>
Date: Wed, 25 Aug 2021 13:01:55 +0200
Subject: [PATCH] Warn if a sensor with state_class_total has a decreasing
 value (#55197)

---
 homeassistant/components/energy/sensor.py   |  7 +++-
 homeassistant/components/sensor/recorder.py | 37 +++++++++++++++++++--
 tests/components/sensor/test_recorder.py    |  6 ++++
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/homeassistant/components/energy/sensor.py b/homeassistant/components/energy/sensor.py
index 099ea8df0ab..45ef8ea5c17 100644
--- a/homeassistant/components/energy/sensor.py
+++ b/homeassistant/components/energy/sensor.py
@@ -298,7 +298,12 @@ class EnergyCostSensor(SensorEntity):
                 )
             return
 
-        if reset_detected(energy, float(self._last_energy_sensor_state)):
+        if reset_detected(
+            self.hass,
+            cast(str, self._config[self._adapter.entity_energy_key]),
+            energy,
+            float(self._last_energy_sensor_state),
+        ):
             # Energy meter was reset, reset cost sensor too
             self._reset(0)
         # Update with newly incurred cost
diff --git a/homeassistant/components/sensor/recorder.py b/homeassistant/components/sensor/recorder.py
index 77f91752327..2115cca2892 100644
--- a/homeassistant/components/sensor/recorder.py
+++ b/homeassistant/components/sensor/recorder.py
@@ -39,6 +39,7 @@ from homeassistant.const import (
     VOLUME_CUBIC_METERS,
 )
 from homeassistant.core import HomeAssistant, State
+from homeassistant.helpers.entity import entity_sources
 import homeassistant.util.dt as dt_util
 import homeassistant.util.pressure as pressure_util
 import homeassistant.util.temperature as temperature_util
@@ -106,6 +107,8 @@ UNIT_CONVERSIONS: dict[str, dict[str, Callable]] = {
     },
 }
 
+# Keep track of entities for which a warning about decreasing value has been logged
+WARN_DIP = "sensor_warn_total_increasing_dip"
 # Keep track of entities for which a warning about unsupported unit has been logged
 WARN_UNSUPPORTED_UNIT = "sensor_warn_unsupported_unit"
 WARN_UNSTABLE_UNIT = "sensor_warn_unstable_unit"
@@ -229,9 +232,36 @@ def _normalize_states(
     return DEVICE_CLASS_UNITS[device_class], fstates
 
 
-def reset_detected(state: float, previous_state: float | None) -> bool:
+def warn_dip(hass: HomeAssistant, entity_id: str) -> None:
+    """Log a warning once if a sensor with state_class_total has a decreasing value."""
+    if WARN_DIP not in hass.data:
+        hass.data[WARN_DIP] = set()
+    if entity_id not in hass.data[WARN_DIP]:
+        hass.data[WARN_DIP].add(entity_id)
+        domain = entity_sources(hass).get(entity_id, {}).get("domain")
+        if domain in ["energy", "growatt_server", "solaredge"]:
+            return
+        _LOGGER.warning(
+            "Entity %s %shas state class total_increasing, but its state is "
+            "not strictly increasing. Please create a bug report at %s",
+            entity_id,
+            f"from integration {domain} " if domain else "",
+            "https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue"
+            "+label%3A%22integration%3A+recorder%22",
+        )
+
+
+def reset_detected(
+    hass: HomeAssistant, entity_id: str, state: float, previous_state: float | None
+) -> bool:
     """Test if a total_increasing sensor has been reset."""
-    return previous_state is not None and state < 0.9 * previous_state
+    if previous_state is None:
+        return False
+
+    if 0.9 * previous_state <= state < previous_state:
+        warn_dip(hass, entity_id)
+
+    return state < 0.9 * previous_state
 
 
 def compile_statistics(
@@ -337,7 +367,8 @@ def compile_statistics(
                         fstate,
                     )
                 elif state_class == STATE_CLASS_TOTAL_INCREASING and (
-                    old_state is None or reset_detected(fstate, new_state)
+                    old_state is None
+                    or reset_detected(hass, entity_id, fstate, new_state)
                 ):
                     reset = True
                     _LOGGER.info(
diff --git a/tests/components/sensor/test_recorder.py b/tests/components/sensor/test_recorder.py
index 5b82fcf0506..0234a8c0613 100644
--- a/tests/components/sensor/test_recorder.py
+++ b/tests/components/sensor/test_recorder.py
@@ -427,6 +427,12 @@ def test_compile_hourly_sum_statistics_total_increasing_small_dip(
         ]
     }
     assert "Error while processing event StatisticsTask" not in caplog.text
+    assert (
+        "Entity sensor.test1 has state class total_increasing, but its state is not "
+        "strictly increasing. Please create a bug report at https://github.com/"
+        "home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A"
+        "+recorder%22"
+    ) in caplog.text
 
 
 def test_compile_hourly_energy_statistics_unsupported(hass_recorder, caplog):