Add this object to MQTT templates (#77142)

* Add `this` object to MQTT templates

* Only set once, remove hass guard

* Set once if there is a state

* Add tests TemplateStateFromEntityId calls once

homeassistant/components/mqtt/models.py

@@ -17,6 +17,8 @@ from homeassistant.helpers.typing import TemplateVarsType
 
 _SENTINEL = object()
 
+ATTR_THIS = "this"
+
 PublishPayloadType = Union[str, bytes, int, float, None]
 
 
@@ -57,7 +59,8 @@ class MqttCommandTemplate:
         entity: Entity | None = None,
     ) -> None:
         """Instantiate a command template."""
-        self._attr_command_template = command_template
+        self._template_state: template.TemplateStateFromEntityId | None = None
+        self._command_template = command_template
         if command_template is None:
             return
 
@@ -91,17 +94,23 @@ class MqttCommandTemplate:
 
             return payload
 
-        if self._attr_command_template is None:
+        if self._command_template is None:
             return value
 
-        values = {"value": value}
+        values: dict[str, Any] = {"value": value}
         if self._entity:
             values[ATTR_ENTITY_ID] = self._entity.entity_id
             values[ATTR_NAME] = self._entity.name
+            if not self._template_state:
+                self._template_state = template.TemplateStateFromEntityId(
+                    self._command_template.hass, self._entity.entity_id
+                )
+            values[ATTR_THIS] = self._template_state
+
         if variables is not None:
             values.update(variables)
         return _convert_outgoing_payload(
-            self._attr_command_template.async_render(values, parse_result=False)
+            self._command_template.async_render(values, parse_result=False)
         )
 
 
@@ -117,6 +126,7 @@ class MqttValueTemplate:
         config_attributes: TemplateVarsType = None,
     ) -> None:
         """Instantiate a value template."""
+        self._template_state: template.TemplateStateFromEntityId | None = None
         self._value_template = value_template
         self._config_attributes = config_attributes
         if value_template is None:
@@ -150,6 +160,11 @@ class MqttValueTemplate:
         if self._entity:
             values[ATTR_ENTITY_ID] = self._entity.entity_id
             values[ATTR_NAME] = self._entity.name
+            if not self._template_state and self._value_template.hass:
+                self._template_state = template.TemplateStateFromEntityId(
+                    self._value_template.hass, self._entity.entity_id
+                )
+            values[ATTR_THIS] = self._template_state
 
         if default == _SENTINEL:
             return self._value_template.async_render_with_possible_json_value(

tests/components/mqtt/test_init.py

@@ -299,7 +299,7 @@ async def test_command_template_variables(hass, mqtt_mock_entry_with_yaml_config
                     "command_topic": topic,
                     "name": "Test Select",
                     "options": ["milk", "beer"],
-                    "command_template": '{"option": "{{ value }}", "entity_id": "{{ entity_id }}", "name": "{{ name }}"}',
+                    "command_template": '{"option": "{{ value }}", "entity_id": "{{ entity_id }}", "name": "{{ name }}", "this_object_state": "{{ this.state }}"}',
                 }
             },
         )
@@ -319,7 +319,7 @@ async def test_command_template_variables(hass, mqtt_mock_entry_with_yaml_config
 
     mqtt_mock.async_publish.assert_called_once_with(
         topic,
-        '{"option": "beer", "entity_id": "select.test_select", "name": "Test Select"}',
+        '{"option": "beer", "entity_id": "select.test_select", "name": "Test Select", "this_object_state": "milk"}',
         0,
         False,
     )
@@ -327,6 +327,20 @@ async def test_command_template_variables(hass, mqtt_mock_entry_with_yaml_config
     state = hass.states.get("select.test_select")
     assert state.state == "beer"
 
+    # Test that TemplateStateFromEntityId is not called again
+    with patch(
+        "homeassistant.helpers.template.TemplateStateFromEntityId", MagicMock()
+    ) as template_state_calls:
+        await hass.services.async_call(
+            "select",
+            "select_option",
+            {"entity_id": "select.test_select", "option": "milk"},
+            blocking=True,
+        )
+        assert template_state_calls.call_count == 0
+        state = hass.states.get("select.test_select")
+        assert state.state == "milk"
+
 
 async def test_value_template_value(hass):
     """Test the rendering of MQTT value template."""
@@ -359,10 +373,25 @@ async def test_value_template_value(hass):
     # test value template with entity
     entity = Entity()
     entity.hass = hass
+    entity.entity_id = "select.test"
     tpl = template.Template("{{ value_json.id }}")
     val_tpl = mqtt.MqttValueTemplate(tpl, entity=entity)
     assert val_tpl.async_render_with_possible_json_value('{"id": 4321}') == "4321"
 
+    # test this object in a template
+    tpl2 = template.Template("{{ this.entity_id }}")
+    val_tpl2 = mqtt.MqttValueTemplate(tpl2, entity=entity)
+    assert val_tpl2.async_render_with_possible_json_value("bla") == "select.test"
+
+    with patch(
+        "homeassistant.helpers.template.TemplateStateFromEntityId", MagicMock()
+    ) as template_state_calls:
+        tpl3 = template.Template("{{ this.entity_id }}")
+        val_tpl3 = mqtt.MqttValueTemplate(tpl3, entity=entity)
+        val_tpl3.async_render_with_possible_json_value("call1")
+        val_tpl3.async_render_with_possible_json_value("call2")
+        assert template_state_calls.call_count == 1
+
 
 async def test_service_call_without_topic_does_not_publish(
     hass, mqtt_mock_entry_no_yaml_config