Improve error handling in CoreBackupReaderWriter (#139508)

homeassistant/components/backup/manager.py

@@ -14,6 +14,7 @@ from itertools import chain
 import json
 from pathlib import Path, PurePath
 import shutil
+import sys
 import tarfile
 import time
 from typing import IO, TYPE_CHECKING, Any, Protocol, TypedDict, cast
@@ -308,6 +309,12 @@ class DecryptOnDowloadNotSupported(BackupManagerError):
     _message = "On-the-fly decryption is not supported for this backup."
 
 
+class BackupManagerExceptionGroup(BackupManagerError, ExceptionGroup):
+    """Raised when multiple exceptions occur."""
+
+    error_code = "multiple_errors"
+
+
 class BackupManager:
     """Define the format that backup managers can have."""
 
@@ -1605,10 +1612,24 @@ class CoreBackupReaderWriter(BackupReaderWriter):
             )
         finally:
             # Inform integrations the backup is done
+            # If there's an unhandled exception, we keep it so we can rethrow it in case
+            # the post backup actions also fail.
+            unhandled_exc = sys.exception()
             try:
-                await manager.async_post_backup_actions()
+                try:
-            except BackupManagerError as err:
+                    await manager.async_post_backup_actions()
-                raise BackupReaderWriterError(str(err)) from err
+                except BackupManagerError as err:
+                    raise BackupReaderWriterError(str(err)) from err
+            except Exception as err:
+                if not unhandled_exc:
+                    raise
+                # If there's an unhandled exception, we wrap both that and the exception
+                # from the post backup actions in an ExceptionGroup so the caller is
+                # aware of both exceptions.
+                raise BackupManagerExceptionGroup(
+                    f"Multiple errors when creating backup: {unhandled_exc}, {err}",
+                    [unhandled_exc, err],
+                ) from None
 
     def _mkdir_and_generate_backup_contents(
         self,

tests/components/backup/test_manager.py

@@ -8,6 +8,7 @@ from dataclasses import replace
 from io import StringIO
 import json
 from pathlib import Path
+import re
 import tarfile
 from typing import Any
 from unittest.mock import (
@@ -35,6 +36,7 @@ from homeassistant.components.backup.agent import BackupAgentError
 from homeassistant.components.backup.const import DATA_MANAGER
 from homeassistant.components.backup.manager import (
     BackupManagerError,
+    BackupManagerExceptionGroup,
     BackupManagerState,
     CreateBackupStage,
     CreateBackupState,
@@ -1646,34 +1648,60 @@ async def test_exception_platform_pre(hass: HomeAssistant) -> None:
     assert str(err.value) == "Error during pre-backup: Test exception"
 
 
+@pytest.mark.parametrize(
+    ("unhandled_error", "expected_exception", "expected_msg"),
+    [
+        (None, BackupManagerError, "Error during post-backup: Test exception"),
+        (
+            HomeAssistantError("Boom"),
+            BackupManagerExceptionGroup,
+            (
+                "Multiple errors when creating backup: Error during pre-backup: Boom, "
+                "Error during post-backup: Test exception (2 sub-exceptions)"
+            ),
+        ),
+        (
+            Exception("Boom"),
+            BackupManagerExceptionGroup,
+            (
+                "Multiple errors when creating backup: Error during pre-backup: Boom, "
+                "Error during post-backup: Test exception (2 sub-exceptions)"
+            ),
+        ),
+    ],
+)
 @pytest.mark.usefixtures("mock_backup_generation")
-async def test_exception_platform_post(hass: HomeAssistant) -> None:
+async def test_exception_platform_post(
+    hass: HomeAssistant,
+    unhandled_error: Exception | None,
+    expected_exception: type[Exception],
+    expected_msg: str,
+) -> None:
     """Test exception in post step."""
 
-    async def _mock_step(hass: HomeAssistant) -> None:
-        raise HomeAssistantError("Test exception")
-
     remote_agent = mock_backup_agent("remote")
     await setup_backup_platform(
         hass,
         domain="test",
         platform=Mock(
-            async_pre_backup=AsyncMock(),
+            # We let the pre_backup fail to test that unhandled errors are not discarded
-            async_post_backup=_mock_step,
+            # when post backup fails
+            async_pre_backup=AsyncMock(side_effect=unhandled_error),
+            async_post_backup=AsyncMock(
+                side_effect=HomeAssistantError("Test exception")
+            ),
             async_get_backup_agents=AsyncMock(return_value=[remote_agent]),
         ),
     )
     await setup_backup_integration(hass)
 
-    with pytest.raises(BackupManagerError) as err:
+    with pytest.raises(expected_exception, match=re.escape(expected_msg)):
         await hass.services.async_call(
             DOMAIN,
             "create",
             blocking=True,
         )
 
-    assert str(err.value) == "Error during post-backup: Test exception"
-
 
 @pytest.mark.parametrize(
     (