Make this usable as an external_component

Since v1.18.0 esphome supports external components which allow you to
use custom components much more easily.

https://esphome.io/components/external_components.html

.gitignore

@@ -30,3 +30,6 @@
 *.exe
 *.out
 *.app
+
+# Python cache
+__pycache__

components/mitsubishi_heatpump/__init__.py

@@ -0,0 +1,46 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import climate
+from esphome.components.logger import HARDWARE_UART_TO_SERIAL
+from esphome.const import CONF_ID, CONF_HARDWARE_UART, CONF_UPDATE_INTERVAL
+from esphome.core import CORE, coroutine
+
+AUTO_LOAD = ["climate"]
+
+MitsubishiHeatPump = cg.global_ns.class_("MitsubishiHeatPump", climate.Climate, cg.PollingComponent)
+
+
+def valid_uart(uart):
+    if CORE.is_esp8266:
+        uarts = ["UART0"] # UART1 is tx-only
+    elif CORE.is_esp32:
+        uarts = ["UART0", "UART1", "UART2"]
+    else:
+        raise NotImplementedError
+
+    return cv.one_of(*uarts, upper=True)(uart)
+
+
+CONFIG_SCHEMA = climate.CLIMATE_SCHEMA.extend(
+    {
+        cv.GenerateID(): cv.declare_id(MitsubishiHeatPump),
+        cv.Optional(CONF_HARDWARE_UART, default="UART0"): valid_uart,
+
+        # If polling interval is greater than 9 seconds, the HeatPump library
+        # reconnects, but doesn't then follow up with our data request.
+        cv.Optional(CONF_UPDATE_INTERVAL, default="500ms"): cv.All(
+            cv.update_interval,
+            cv.Range(max=cv.TimePeriod(milliseconds=9000))
+        ),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+@coroutine
+def to_code(config):
+    serial = HARDWARE_UART_TO_SERIAL[config[CONF_HARDWARE_UART]]
+    var = cg.new_Pvariable(config[CONF_ID], cg.RawExpression(f'&{serial}'))
+    yield cg.register_component(var, config)
+    yield climate.register_climate(var, config)
+    cg.add_library("https://github.com/SwiCago/HeatPump", None)
+