Support numeric sensors with no unit_of_measurement in prometheus (#60157)

homeassistant/components/prometheus/__init__.py

@@ -418,9 +418,11 @@ class PrometheusMetrics:
                 break
 
         if metric is not None:
-            _metric = self._metric(
-                metric, self.prometheus_cli.Gauge, f"Sensor data measured in {unit}"
-            )
+            documentation = "State of the sensor"
+            if unit:
+                documentation = f"Sensor data measured in {unit}"
+
+            _metric = self._metric(metric, self.prometheus_cli.Gauge, documentation)
 
             try:
                 value = self.state_as_number(state)
@@ -458,8 +460,12 @@ class PrometheusMetrics:
     def _sensor_fallback_metric(state, unit):
         """Get metric from fallback logic for compatibility."""
         if unit in (None, ""):
-            _LOGGER.debug("Unsupported sensor: %s", state.entity_id)
-            return None
+            try:
+                state_helper.state_as_number(state)
+            except ValueError:
+                _LOGGER.debug("Unsupported sensor: %s", state.entity_id)
+                return None
+            return "sensor_state"
         return f"sensor_unit_{unit}"
 
     @staticmethod

tests/components/prometheus/test_init.py

@@ -100,6 +100,21 @@ async def prometheus_client(hass, hass_client, namespace):
     sensor5.entity_id = "sensor.sps30_pm_1um_weight_concentration"
     await sensor5.async_update_ha_state()
 
+    sensor6 = DemoSensor(None, "Trend Gradient", 0.002, None, None, None, None)
+    sensor6.hass = hass
+    sensor6.entity_id = "sensor.trend_gradient"
+    await sensor6.async_update_ha_state()
+
+    sensor7 = DemoSensor(None, "Text", "should_not_work", None, None, None, None)
+    sensor7.hass = hass
+    sensor7.entity_id = "sensor.text"
+    await sensor7.async_update_ha_state()
+
+    sensor8 = DemoSensor(None, "Text Unit", "should_not_work", None, None, "Text", None)
+    sensor8.hass = hass
+    sensor8.entity_id = "sensor.text_unit"
+    await sensor8.async_update_ha_state()
+
     number1 = DemoNumber(None, "Threshold", 5.2, None, False, 0, 10, 0.1)
     number1.hass = hass
     number1.entity_id = "input_number.threshold"
@@ -241,6 +256,24 @@ async def test_view_empty_namespace(hass, hass_client):
         'friendly_name="SPS30 PM <1µm Weight concentration"} 3.7069' in body
     )
 
+    assert (
+        'sensor_state{domain="sensor",'
+        'entity="sensor.trend_gradient",'
+        'friendly_name="Trend Gradient"} 0.002' in body
+    )
+
+    assert (
+        'sensor_state{domain="sensor",'
+        'entity="sensor.text",'
+        'friendly_name="Text"} 0' not in body
+    )
+
+    assert (
+        'sensor_unit_text{domain="sensor",'
+        'entity="sensor.text_unit",'
+        'friendly_name="Text Unit"} 0' not in body
+    )
+
     assert (
         'input_number_state{domain="input_number",'
         'entity="input_number.threshold",'