From d26c7a0536983847832352f58a3e877b95dab4e4 Mon Sep 17 00:00:00 2001
From: Jan Bouwhuis <jbouwh@users.noreply.github.com>
Date: Thu, 28 Nov 2024 08:27:24 +0100
Subject: [PATCH] Log warning if via_device reference not exists when creating
 or updating a device registry entry (#131746)

---
 homeassistant/helpers/device_registry.py | 11 +++++-
 tests/helpers/test_device_registry.py    | 50 +++++++++++++++++++++++-
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/homeassistant/helpers/device_registry.py b/homeassistant/helpers/device_registry.py
index 0e56adc7377..5dfd5d9e8a9 100644
--- a/homeassistant/helpers/device_registry.py
+++ b/homeassistant/helpers/device_registry.py
@@ -38,6 +38,7 @@ from .deprecation import (
     check_if_deprecated_constant,
     dir_with_deprecated_constants,
 )
+from .frame import ReportBehavior, report_usage
 from .json import JSON_DUMP, find_paths_unserializable_data, json_bytes, json_fragment
 from .registry import BaseRegistry, BaseRegistryItems, RegistryIndexType
 from .singleton import singleton
@@ -821,7 +822,15 @@ class DeviceRegistry(BaseRegistry[dict[str, list[dict[str, Any]]]]):
             name = default_name
 
         if via_device is not None and via_device is not UNDEFINED:
-            via = self.async_get_device(identifiers={via_device})
+            if (via := self.async_get_device(identifiers={via_device})) is None:
+                report_usage(
+                    "calls `device_registry.async_get_or_create` referencing a "
+                    f"non existing `via_device` {via_device}, "
+                    f"with device info: {device_info}",
+                    core_behavior=ReportBehavior.LOG,
+                    breaks_in_ha_version="2025.12.0",
+                )
+
             via_device_id: str | UndefinedType = via.id if via else UNDEFINED
         else:
             via_device_id = UNDEFINED
diff --git a/tests/helpers/test_device_registry.py b/tests/helpers/test_device_registry.py
index 837400d502d..2335b1b93bd 100644
--- a/tests/helpers/test_device_registry.py
+++ b/tests/helpers/test_device_registry.py
@@ -1482,7 +1482,9 @@ async def test_removing_area_id(
 
 
 async def test_specifying_via_device_create(
-    hass: HomeAssistant, device_registry: dr.DeviceRegistry
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+    caplog: pytest.LogCaptureFixture,
 ) -> None:
     """Test specifying a via_device and removal of the hub device."""
     config_entry_1 = MockConfigEntry()
@@ -1513,9 +1515,32 @@ async def test_specifying_via_device_create(
     light = device_registry.async_get_device(identifiers={("hue", "456")})
     assert light.via_device_id is None
 
+    # A device with a non existing via_device reference should create
+    light_via_nonexisting_parent_device = device_registry.async_get_or_create(
+        config_entry_id=config_entry_2.entry_id,
+        connections=set(),
+        identifiers={("hue", "789")},
+        manufacturer="manufacturer",
+        model="light",
+        via_device=("hue", "non_existing_123"),
+    )
+    assert {
+        "calls `device_registry.async_get_or_create` "
+        "referencing a non existing `via_device` "
+        '("hue","non_existing_123")' in caplog.text
+    }
+    assert light_via_nonexisting_parent_device is not None
+    assert light_via_nonexisting_parent_device.via_device_id is None
+    nonexisting_parent_device = device_registry.async_get_device(
+        identifiers={("hue", "non_existing_123")}
+    )
+    assert nonexisting_parent_device is None
+
 
 async def test_specifying_via_device_update(
-    hass: HomeAssistant, device_registry: dr.DeviceRegistry
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+    caplog: pytest.LogCaptureFixture,
 ) -> None:
     """Test specifying a via_device and updating."""
     config_entry_1 = MockConfigEntry()
@@ -1529,6 +1554,7 @@ async def test_specifying_via_device_update(
         identifiers={("hue", "456")},
         manufacturer="manufacturer",
         model="light",
+        name="Light",
         via_device=("hue", "0123"),
     )
 
@@ -1552,6 +1578,26 @@ async def test_specifying_via_device_update(
     )
 
     assert light.via_device_id == via.id
+    assert light.name == "Light"
+
+    # Try updating with a non existing via device
+    light = device_registry.async_get_or_create(
+        config_entry_id=config_entry_2.entry_id,
+        connections=set(),
+        identifiers={("hue", "456")},
+        manufacturer="manufacturer",
+        model="light",
+        name="New light",
+        via_device=("hue", "non_existing_abc"),
+    )
+    assert {
+        "calls `device_registry.async_get_or_create` "
+        "referencing a non existing `via_device` "
+        '("hue","non_existing_123")' in caplog.text
+    }
+    # Assert the name was updated correctly
+    assert light.via_device_id == via.id
+    assert light.name == "New light"
 
 
 async def test_loading_saving_data(