Allow exporting of `update` domain to Prometheus (#99400)

homeassistant/components/prometheus/__init__.py

@@ -671,6 +671,15 @@ class PrometheusMetrics:
 
         metric.labels(**self._labels(state)).set(self.state_as_number(state))
 
+    def _handle_update(self, state):
+        metric = self._metric(
+            "update_state",
+            self.prometheus_cli.Gauge,
+            "Update state, indicating if an update is available (0/1)",
+        )
+        value = self.state_as_number(state)
+        metric.labels(**self._labels(state)).set(value)
+
 
 class PrometheusView(HomeAssistantView):
     """Handle Prometheus requests."""

tests/components/prometheus/test_init.py

@@ -24,6 +24,7 @@ from homeassistant.components import (
     prometheus,
     sensor,
     switch,
+    update,
 )
 from homeassistant.components.climate import (
     ATTR_CURRENT_TEMPERATURE,
@@ -572,6 +573,23 @@ async def test_counter(client, counter_entities) -> None:
     )
 
 
+@pytest.mark.parametrize("namespace", [""])
+async def test_update(client, update_entities) -> None:
+    """Test prometheus metrics for update."""
+    body = await generate_latest_metrics(client)
+
+    assert (
+        'update_state{domain="update",'
+        'entity="update.firmware",'
+        'friendly_name="Firmware"} 1.0' in body
+    )
+    assert (
+        'update_state{domain="update",'
+        'entity="update.addon",'
+        'friendly_name="Addon"} 0.0' in body
+    )
+
+
 @pytest.mark.parametrize("namespace", [""])
 async def test_renaming_entity_name(
     hass: HomeAssistant,
@@ -1591,6 +1609,36 @@ async def counter_fixture(
     return data
 
 
+@pytest.fixture(name="update_entities")
+async def update_fixture(
+    hass: HomeAssistant, entity_registry: er.EntityRegistry
+) -> dict[str, er.RegistryEntry]:
+    """Simulate update entities."""
+    data = {}
+    update_1 = entity_registry.async_get_or_create(
+        domain=update.DOMAIN,
+        platform="test",
+        unique_id="update_1",
+        suggested_object_id="firmware",
+        original_name="Firmware",
+    )
+    set_state_with_entry(hass, update_1, STATE_ON)
+    data["update_1"] = update_1
+
+    update_2 = entity_registry.async_get_or_create(
+        domain=update.DOMAIN,
+        platform="test",
+        unique_id="update_2",
+        suggested_object_id="addon",
+        original_name="Addon",
+    )
+    set_state_with_entry(hass, update_2, STATE_OFF)
+    data["update_2"] = update_2
+
+    await hass.async_block_till_done()
+    return data
+
+
 def set_state_with_entry(
     hass: HomeAssistant,
     entry: er.RegistryEntry,