feat: Improve config flow validation, error handling, and reconfigure UX

- Validate and normalise the host field before connecting: strip
  whitespace, reject URLs containing :// or /
- Map connection errors to granular user-visible error keys
  (invalid_host / cannot_connect / invalid_inverter) with translated
  messages in strings.json and translations/en.json
- Move serial number read inside the try block so client.close() always
  runs on failure
- Set a unique ID from the inverter serial number on first setup so HA
  can detect duplicate entries
- Add async_step_reconfigure so users can update the inverter host
  in-place without removing and re-adding the integration

Author: davidnoyes

custom_components/givenergy_local/config_flow.py

@@ -3,6 +3,9 @@
 from __future__ import annotations
 
 import asyncio
+from collections.abc import Mapping
+from enum import StrEnum
+import socket
 
 from typing import Any
 
@@ -11,19 +14,78 @@
 
 from .const import CONF_HOST, DOMAIN, LOGGER
 from .givenergy_modbus.client.client import Client
+from .givenergy_modbus.exceptions import CommunicationError
 
 STEP_USER_DATA_SCHEMA = vol.Schema({vol.Required(CONF_HOST): str})
+STEP_RECONFIGURE_DATA_SCHEMA = vol.Schema({vol.Required(CONF_HOST): str})
+
+
+class ConfigFlowError(StrEnum):
+    """User-visible config flow error keys."""
+
+    CANNOT_CONNECT = "cannot_connect"
+    INVALID_HOST = "invalid_host"
+    INVALID_INVERTER = "invalid_inverter"
+    ALREADY_CONFIGURED = "already_configured"
+    DIFFERENT_INVERTER = "different_inverter"
+
+
+class InvalidInverterError(Exception):
+    """Raised when a host responds, but not like a usable inverter."""
+
+
+def _normalise_host(host: str) -> str:
+    """Normalise and sanity-check host input before connecting."""
+    normalised_host = host.strip()
+
+    if not normalised_host:
+        raise ValueError("Host cannot be blank")
+
+    if "://" in normalised_host or "/" in normalised_host:
+        raise ValueError("Host must be a hostname or IP address")
+
+    return normalised_host
+
+
+def _map_validation_error(err: Exception) -> ConfigFlowError:
+    """Map internal validation failures to translated config-flow errors."""
+    if isinstance(err, (ValueError, socket.gaierror)):
+        return ConfigFlowError.INVALID_HOST
+
+    if isinstance(
+        err, (CommunicationError, TimeoutError, OSError, asyncio.TimeoutError)
+    ):
+        return ConfigFlowError.CANNOT_CONNECT
+
+    if isinstance(err, (AttributeError, InvalidInverterError)):
+        return ConfigFlowError.INVALID_INVERTER
+
+    return ConfigFlowError.CANNOT_CONNECT
+
+
+async def _validate_input(data: Mapping[str, Any]) -> tuple[dict[str, Any], str]:
+    """Validate and normalise user input, returning clean data and inverter serial."""
+    validated_data = dict(data)
+    validated_data[CONF_HOST] = _normalise_host(str(data[CONF_HOST]))
+
+    serial_no = (await read_inverter_serial(validated_data)).strip()
+    if not serial_no:
+        raise InvalidInverterError("Inverter serial number was blank")
+
+    return validated_data, serial_no
 
 
 async def read_inverter_serial(data: dict[str, Any]) -> str:
     """Validate user input by reading the inverter serial number."""
     client = Client(data[CONF_HOST], 8899)
-    async with asyncio.timeout(10):
-        await client.connect()
-        await client.detect_plant()
+    try:
+        async with asyncio.timeout(10):
+            await client.connect()
+            await client.detect_plant()
+        serial_no: str = client.plant.inverter.serial_number
+    finally:
         await client.close()
 
-    serial_no: str = client.plant.inverter.serial_number
     return serial_no
 
 
@@ -41,16 +103,18 @@ async def async_step_user(
                 step_id="user", data_schema=STEP_USER_DATA_SCHEMA
             )
 
-        errors = {}
+        errors: dict[str, str] = {}
 
         try:
-            serial_no = await read_inverter_serial(user_input)
-        except Exception:  # pylint: disable=broad-except
+            validated_input, serial_no = await _validate_input(user_input)
+        except Exception as err:  # pylint: disable=broad-except
             LOGGER.exception("Failed to validate inverter configuration")
-            errors["base"] = "cannot_connect"
+            errors["base"] = _map_validation_error(err)
         else:
+            await self.async_set_unique_id(serial_no)
+            self._abort_if_unique_id_configured()
             return self.async_create_entry(
-                title=f"Solar Inverter (S/N {serial_no})", data=user_input
+                title=f"Solar Inverter (S/N {serial_no})", data=validated_input
             )
 
         return self.async_show_form(
@@ -60,3 +124,51 @@ async def async_step_user(
             ),
             errors=errors,
         )
+
+    async def async_step_reconfigure(
+        self, user_input: dict[str, Any] | None = None
+    ) -> ConfigFlowResult:
+        """Allow users to update the configured inverter host in place."""
+        entry = self._get_reconfigure_entry()
+
+        if user_input is None:
+            return self.async_show_form(
+                step_id="reconfigure",
+                data_schema=self.add_suggested_values_to_schema(
+                    STEP_RECONFIGURE_DATA_SCHEMA,
+                    {CONF_HOST: entry.data.get(CONF_HOST, "")},
+                ),
+            )
+
+        errors: dict[str, str] = {}
+
+        try:
+            validated_input, serial_no = await _validate_input(user_input)
+        except Exception as err:  # pylint: disable=broad-except
+            LOGGER.exception("Failed to validate inverter reconfiguration")
+            errors["base"] = _map_validation_error(err)
+        else:
+            existing_entry = await self.async_set_unique_id(
+                serial_no, raise_on_progress=False
+            )
+            if existing_entry is not None and existing_entry.entry_id != entry.entry_id:
+                return self.async_abort(reason=ConfigFlowError.ALREADY_CONFIGURED)
+            if entry.unique_id is not None:
+                self._abort_if_unique_id_mismatch(
+                    reason=ConfigFlowError.DIFFERENT_INVERTER
+                )
+
+            return self.async_update_reload_and_abort(
+                entry,
+                unique_id=serial_no,
+                data={**entry.data, **validated_input},
+                title=f"Solar Inverter (S/N {serial_no})",
+            )
+
+        return self.async_show_form(
+            step_id="reconfigure",
+            data_schema=self.add_suggested_values_to_schema(
+                STEP_RECONFIGURE_DATA_SCHEMA, user_input
+            ),
+            errors=errors,
+        )

custom_components/givenergy_local/strings.json

@@ -1,13 +1,40 @@
 {
   "config": {
     "step": {
+      "user": {
+        "title": "Connect to inverter",
+        "data": {
+          "host": "Host"
+        },
+        "data_description": {
+          "host": "Enter the inverter hostname or IP address only, without http:// or a port."
+        }
+      },
+      "reconfigure": {
+        "title": "Update inverter connection",
+        "description": "Update the saved host for this inverter.",
+        "data": {
+          "host": "Host"
+        },
+        "data_description": {
+          "host": "Enter the new inverter hostname or IP address only, without http:// or a port."
+        }
+      },
       "confirm": {
         "description": "[%key:common::config_flow::description::confirm_setup%]"
       }
     },
+    "error": {
+      "cannot_connect": "Failed to connect to the inverter.",
+      "invalid_host": "Enter a valid inverter hostname or IP address.",
+      "invalid_inverter": "The device responded, but it did not behave like a supported GivEnergy inverter."
+    },
     "abort": {
+      "already_configured": "This inverter is already configured.",
+      "different_inverter": "The new host belongs to a different inverter. Use the original inverter host for this entry.",
+      "reconfigure_successful": "The inverter connection settings were updated.",
       "single_instance_allowed": "[%key:common::config_flow::abort::single_instance_allowed%]",
       "no_devices_found": "[%key:common::config_flow::abort::no_devices_found%]"
     }
   }
-}
+}

custom_components/givenergy_local/translations/en.json

@@ -4,13 +4,32 @@
             "user": {
                 "title": "Connect to inverter",
                 "data": {
-                    "host": "Host",
-                    "num_batteries": "Number of batteries"
+                    "host": "Host"
+                },
+                "data_description": {
+                    "host": "Enter the inverter hostname or IP address only, without http:// or a port."
+                }
+            },
+            "reconfigure": {
+                "title": "Update inverter connection",
+                "description": "Update the saved host for this inverter.",
+                "data": {
+                    "host": "Host"
+                },
+                "data_description": {
+                    "host": "Enter the new inverter hostname or IP address only, without http:// or a port."
                 }
             }
         },
         "error": {
-            "cannot_connect": "Failed to connect to the inverter."
+            "cannot_connect": "Failed to connect to the inverter.",
+            "invalid_host": "Enter a valid inverter hostname or IP address.",
+            "invalid_inverter": "The device responded, but it did not behave like a supported GivEnergy inverter."
+        },
+        "abort": {
+            "already_configured": "This inverter is already configured.",
+            "different_inverter": "The new host belongs to a different inverter. Use the original inverter host for this entry.",
+            "reconfigure_successful": "The inverter connection settings were updated."
         }
     }
-}
+}