Avoid redundant calls to async_write_ha_state in mqtt siren (#100813)

* Avoid redundant calls to async_write_ha_state

* Add comment

tests/components/mqtt/test_siren.py

@@ -44,6 +44,7 @@ from .test_common import (
     help_test_setting_attribute_via_mqtt_json_message,
     help_test_setting_attribute_with_template,
     help_test_setting_blocked_attribute_via_mqtt_json_message,
+    help_test_skipped_async_ha_write_state,
     help_test_unique_id,
     help_test_unload_config_entry_with_platform,
     help_test_update_with_json_attrs_bad_json,
@@ -1092,3 +1093,53 @@ async def test_unload_entry(
     await help_test_unload_config_entry_with_platform(
         hass, mqtt_mock_entry, domain, config
     )
+
+
+@pytest.mark.parametrize(
+    "hass_config",
+    [
+        help_custom_config(
+            siren.DOMAIN,
+            DEFAULT_CONFIG,
+            (
+                {
+                    "state_topic": "test-topic",
+                    "available_tones": ["siren", "bell"],
+                    "availability_topic": "availability-topic",
+                    "json_attributes_topic": "json-attributes-topic",
+                },
+            ),
+        )
+    ],
+)
+@pytest.mark.parametrize(
+    ("topic", "payload1", "payload2"),
+    [
+        ("availability-topic", "online", "offline"),
+        ("json-attributes-topic", '{"attr1": "val1"}', '{"attr1": "val2"}'),
+        ("test-topic", "ON", "OFF"),
+        ("test-topic", '{"state": "ON"}', '{"state": "OFF"}'),
+        ("test-topic", '{"state":"ON","tone":"siren"}', '{"state":"ON","tone":"bell"}'),
+        (
+            "test-topic",
+            '{"state":"ON","tone":"siren"}',
+            '{"state":"OFF","tone":"siren"}',
+        ),
+        # Attriute volume_level 2 is invalid, but the state is valid and should update
+        (
+            "test-topic",
+            '{"state":"ON","volume_level":0.5}',
+            '{"state":"OFF","volume_level":2}',
+        ),
+    ],
+)
+async def test_skipped_async_ha_write_state(
+    hass: HomeAssistant,
+    mqtt_mock_entry: MqttMockHAClientGenerator,
+    topic: str,
+    payload1: str,
+    payload2: str,
+) -> None:
+    """Test a write state command is only called when there is change."""
+    await mqtt_mock_entry()
+    await help_test_skipped_async_ha_write_state(hass, topic, payload1, payload2)