Add native ESPHome API component (#19334)

* Create esphomelib component

* Update requirements

* Remove python 2 string literals

* MVP

* Remove config flow

* Remove config flow translations

* Use dispatcher more

* Use data classes

* Type Hints

* Cleanup on remove

* Use helper and cleanup

* Fix HA stop listener cleanup

* Add config flow

* Fix SyntaxError for Py3.5

* Update

* Lint

* Re-do tests

* ✨ Rename to ESPHome

* Better error message for resolve errors

* Fix tests when aioesphomeapi not installed

* Refactor mock

* Update requirements

* Add strings.json

* 🍵 100% config flow  test coverage

homeassistant/components/sensor/esphome.py

@@ -0,0 +1,62 @@
+"""Support for esphome sensors."""
+import logging
+import math
+from typing import Optional, TYPE_CHECKING
+
+from homeassistant.components.esphome import EsphomeEntity, \
+    platform_async_setup_entry
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.helpers.typing import HomeAssistantType
+
+if TYPE_CHECKING:
+    # pylint: disable=unused-import
+    from aioesphomeapi import SensorInfo, SensorState  # noqa
+
+DEPENDENCIES = ['esphome']
+_LOGGER = logging.getLogger(__name__)
+
+
+async def async_setup_entry(hass: HomeAssistantType,
+                            entry: ConfigEntry, async_add_entities) -> None:
+    """Set up esphome sensors based on a config entry."""
+    # pylint: disable=redefined-outer-name
+    from aioesphomeapi import SensorInfo, SensorState  # noqa
+
+    await platform_async_setup_entry(
+        hass, entry, async_add_entities,
+        component_key='sensor',
+        info_type=SensorInfo, entity_type=EsphomeSensor,
+        state_type=SensorState
+    )
+
+
+class EsphomeSensor(EsphomeEntity):
+    """A sensor implementation for esphome."""
+
+    @property
+    def _static_info(self) -> 'SensorInfo':
+        return super()._static_info
+
+    @property
+    def _state(self) -> Optional['SensorState']:
+        return super()._state
+
+    @property
+    def icon(self) -> str:
+        """Return the icon."""
+        return self._static_info.icon
+
+    @property
+    def state(self) -> Optional[str]:
+        """Return the state of the entity."""
+        if self._state is None:
+            return None
+        if math.isnan(self._state.state):
+            return None
+        return '{:.{prec}f}'.format(
+            self._state.state, prec=self._static_info.accuracy_decimals)
+
+    @property
+    def unit_of_measurement(self) -> str:
+        """Return the unit the value is expressed in."""
+        return self._static_info.unit_of_measurement