Add diagnostics to KNX (#64471)

.coveragerc

@@ -557,6 +557,7 @@ omit =
     homeassistant/components/knx/__init__.py
     homeassistant/components/knx/climate.py
     homeassistant/components/knx/cover.py
+    homeassistant/components/knx/diagnostics.py
     homeassistant/components/knx/expose.py
     homeassistant/components/knx/knx_entity.py
     homeassistant/components/knx/light.py

homeassistant/components/knx/diagnostics.py

@@ -0,0 +1,41 @@
+"""Diagnostics support for KNX."""
+from __future__ import annotations
+
+from typing import Any
+
+import voluptuous as vol
+
+from homeassistant import config as conf_util
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers.system_info import async_get_system_info
+
+from . import CONFIG_SCHEMA
+from .const import DOMAIN
+
+
+async def async_get_config_entry_diagnostics(
+    hass: HomeAssistant, config_entry: ConfigEntry
+) -> dict:
+    """Return diagnostics for a config entry."""
+    diag: dict[str, Any] = {}
+    diag["home_assistant"] = await async_get_system_info(hass)
+
+    knx_module = hass.data[DOMAIN]
+    diag["xknx"] = {
+        "version": knx_module.xknx.version,
+        "current_address": str(knx_module.xknx.current_address),
+    }
+
+    diag["config_entry_data"] = dict(config_entry.data)
+
+    raw_config = await conf_util.async_hass_config_yaml(hass)
+    diag["configuration_yaml"] = raw_config.get(DOMAIN)
+    try:
+        CONFIG_SCHEMA(raw_config)
+    except vol.Invalid as ex:
+        diag["configuration_error"] = str(ex)
+    else:
+        diag["configuration_error"] = None
+
+    return diag