Download backup if restore fails in Z-Wave migration (#145434)

* ZWaveJS migration: Download backup if restore fails

* update test

* PR comment

homeassistant/components/zwave_js/config_flow.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import asyncio
+import base64
 from contextlib import suppress
 from datetime import datetime
 import logging
@@ -192,7 +193,7 @@ class ZWaveJSConfigFlow(ConfigFlow, domain=DOMAIN):
         self.backup_task: asyncio.Task | None = None
         self.restore_backup_task: asyncio.Task | None = None
         self.backup_data: bytes | None = None
-        self.backup_filepath: str | None = None
+        self.backup_filepath: Path | None = None
         self.use_addon = False
         self._migrating = False
         self._reconfigure_config_entry: ConfigEntry | None = None
@@ -1241,11 +1242,15 @@ class ZWaveJSConfigFlow(ConfigFlow, domain=DOMAIN):
         """Restore failed."""
         if user_input is not None:
             return await self.async_step_restore_nvm()
+        assert self.backup_filepath is not None
+        assert self.backup_data is not None
 
         return self.async_show_form(
             step_id="restore_failed",
             description_placeholders={
                 "file_path": str(self.backup_filepath),
+                "file_url": f"data:application/octet-stream;base64,{base64.b64encode(self.backup_data).decode('ascii')}",
+                "file_name": self.backup_filepath.name,
             },
         )
 
@@ -1383,12 +1388,14 @@ class ZWaveJSConfigFlow(ConfigFlow, domain=DOMAIN):
             unsub()
 
         # save the backup to a file just in case
-        self.backup_filepath = self.hass.config.path(
-            f"zwavejs_nvm_backup_{datetime.now().strftime('%Y-%m-%d_%H-%M-%S')}.bin"
+        self.backup_filepath = Path(
+            self.hass.config.path(
+                f"zwavejs_nvm_backup_{datetime.now().strftime('%Y-%m-%d_%H-%M-%S')}.bin"
+            )
         )
         try:
             await self.hass.async_add_executor_job(
-                Path(self.backup_filepath).write_bytes,
+                self.backup_filepath.write_bytes,
                 self.backup_data,
             )
         except OSError as err:

homeassistant/components/zwave_js/strings.json

@@ -123,7 +123,7 @@
       },
       "restore_failed": {
         "title": "Restoring unsuccessful",
-        "description": "Your Z-Wave network could not be restored to the new controller. This means that your Z-Wave devices are not connected to Home Assistant.\n\nThe backup is saved to ”{file_path}”",
+        "description": "Your Z-Wave network could not be restored to the new controller. This means that your Z-Wave devices are not connected to Home Assistant.\n\nThe backup is saved to ”{file_path}”\n\n'<'a href=\"{file_url}\" download=\"{file_name}\"'>'Download backup file'<'/a'>'",
         "submit": "Try again"
       },
       "choose_serial_port": {

tests/components/zwave_js/test_config_flow.py

@@ -4231,6 +4231,8 @@ async def test_reconfigure_migrate_restore_failure(
     description_placeholders = result["description_placeholders"]
     assert description_placeholders is not None
     assert description_placeholders["file_path"]
+    assert description_placeholders["file_url"]
+    assert description_placeholders["file_name"]
 
     result = await hass.config_entries.flow.async_configure(result["flow_id"], {})