Allow linking template helpers to child devices (#179590)

homeassistant/components/template/entity.py

@@ -88,12 +88,13 @@ class AbstractTemplateEntity(Entity):
             )
 
         device_registry = dr.async_get(hass)
+        # Allow linking to a main or child device, but not to a composite device.
         if (
-            device_id := config.get(CONF_DEVICE_ID)
-        ) is not None and device_registry.async_is_composite_device_id(
-            device_id
-        ) is False:
-            self.device_entry = device_registry.async_get(device_id)
+            (device_id := config.get(CONF_DEVICE_ID)) is not None
+            and (device_entry := device_registry.async_get(device_id)) is not None
+            and not device_registry.async_is_composite_device_id(device_id)
+        ):
+            self.device_entry = device_entry
 
     @property
     @abstractmethod

homeassistant/components/template/repairs.py

@@ -41,9 +41,9 @@ class CompositeDeviceIdRepairFlow(RepairsFlow):
         errors: dict[str, str] = {}
         if user_input is not None:
             device_id = user_input.get(CONF_DEVICE_ID)
-            if (
-                device_id is None
-                or device_registry.async_is_composite_device_id(device_id) is False
+            if device_id is None or (
+                device_registry.async_get(device_id) is not None
+                and not device_registry.async_is_composite_device_id(device_id)
             ):
                 options = {**entry.options}
                 if device_id:

tests/components/template/test_init.py

@@ -492,6 +492,56 @@ async def test_change_device(
     )
 
 
+@pytest.mark.parametrize(
+    "linked_device",
+    [
+        pytest.param("main", id="main_device"),
+        pytest.param("child", id="child_device"),
+    ],
+)
+async def test_link_to_main_or_child_device(
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+    entity_registry: er.EntityRegistry,
+    linked_device: str,
+) -> None:
+    """Test a template entity links to a selected main or child device."""
+    source_entry = MockConfigEntry()
+    source_entry.add_to_hass(hass)
+    main_device = device_registry.async_get_or_create(
+        config_entry_id=source_entry.entry_id,
+        identifiers={("test", "main")},
+    )
+    child_device = device_registry.async_get_or_create_child(
+        config_entry_id=source_entry.entry_id,
+        identifiers={("test", "child")},
+        parent_device_id=main_device.id,
+    )
+    selected_device_id = {"main": main_device, "child": child_device}[linked_device].id
+
+    template_config_entry = MockConfigEntry(
+        domain=DOMAIN,
+        options={
+            "name": "My template",
+            "state": "{{10}}",
+            "template_type": "sensor",
+            "device_id": selected_device_id,
+        },
+        title="Template",
+    )
+    template_config_entry.add_to_hass(hass)
+    assert await hass.config_entries.async_setup(template_config_entry.entry_id)
+    await hass.async_block_till_done()
+
+    template_entities = list(
+        entity_registry.entities.get_entries_for_config_entry_id(
+            template_config_entry.entry_id
+        )
+    )
+    assert len(template_entities) == 1
+    assert template_entities[0].device_id == selected_device_id
+
+
 async def test_setup_removes_stale_helper_device(
     hass: HomeAssistant,
     device_registry: dr.DeviceRegistry,

tests/components/template/test_repairs.py

@@ -176,6 +176,53 @@ async def test_composite_device_id_repair_flow(
     assert entity_entry.device_id == picked_device_id
 
 
+@pytest.mark.usefixtures("split_devices")
+async def test_composite_device_id_repair_flow_links_child_device(
+    hass: HomeAssistant,
+    hass_client: ClientSessionGenerator,
+    device_registry: dr.DeviceRegistry,
+    entity_registry: er.EntityRegistry,
+    issue_registry: ir.IssueRegistry,
+) -> None:
+    """Test the repair flow accepts a child device and links the entity to it."""
+    source_entry = MockConfigEntry(domain="itg3")
+    source_entry.add_to_hass(hass)
+    parent_device = device_registry.async_get_or_create(
+        config_entry_id=source_entry.entry_id,
+        identifiers={("itg3", "parent")},
+    )
+    child_device = device_registry.async_get_or_create_child(
+        config_entry_id=source_entry.entry_id,
+        identifiers={("itg3", "child")},
+        parent_device_id=parent_device.id,
+    )
+
+    entry = await _setup_template_entry(hass, COMPOSITE_ID)
+    issue_id = f"composite_device_id_{entry.entry_id}"
+    assert issue_registry.async_get_issue(DOMAIN, issue_id)
+
+    assert await async_setup_component(hass, "repairs", {})
+    await hass.async_block_till_done()
+    client = await hass_client()
+
+    result = await start_repair_fix_flow(client, DOMAIN, issue_id)
+    assert result["type"] == FlowResultType.FORM
+    assert result["step_id"] == "select_device"
+
+    result = await process_repair_fix_flow(
+        client, result["flow_id"], json={CONF_DEVICE_ID: child_device.id}
+    )
+    assert result["type"] == FlowResultType.CREATE_ENTRY
+    await hass.async_block_till_done()
+
+    assert entry.options[CONF_DEVICE_ID] == child_device.id
+    assert not issue_registry.async_get_issue(DOMAIN, issue_id)
+
+    entity_entry = entity_registry.async_get(TEMPLATE_ENTITY_ID)
+    assert entity_entry is not None
+    assert entity_entry.device_id == child_device.id
+
+
 async def test_composite_device_id_repair_flow_ambiguity_not_resolved(
     hass: HomeAssistant,
     hass_client: ClientSessionGenerator,