Fix re-adding previously removed child

homeassistant/components/tplink/coordinator.py

@@ -62,6 +62,7 @@ def __init__(
             ),
         )
         self._previous_child_device_ids = {child.device_id for child in device.children}
+        self.removed_child_device_ids: set[str] = set()
         self._child_coordinators: dict[str, TPLinkDataUpdateCoordinator] = {}
 
     async def _async_update_data(self) -> None:
@@ -107,6 +108,7 @@ async def _async_update_data(self) -> None:
                     await child_coordinator.async_shutdown()
 
             self._previous_child_device_ids = current_child_device_ids
+            self.removed_child_device_ids = stale_device_ids
 
     def get_child_coordinator(
         self,

homeassistant/components/tplink/entity.py

@@ -456,6 +456,10 @@ def entities_for_device_and_its_children[
                 )
             )
 
+        # Remove any device ids removed via the coordinator so they can be re-added
+        for removed_child_id in coordinator.removed_child_device_ids:
+            known_child_device_ids.discard(removed_child_id)
+
         current_child_devices = {child.device_id: child for child in device.children}
         current_child_device_ids = set(current_child_devices.keys())
         new_child_device_ids = current_child_device_ids - known_child_device_ids

tests/components/tplink/test_init.py

@@ -917,7 +917,7 @@ async def test_automatic_device_addition_and_removal(
 
     assert device_registry.async_get_device(identifiers={(DOMAIN, "child2")}) is None
 
-    # Add a child devices
+    # Add child devices
     mock_device.children = [children["child1"], children["child3"], children["child4"]]
     freezer.tick(5)
     async_fire_time_changed(hass)
@@ -930,3 +930,22 @@ async def test_automatic_device_addition_and_removal(
 
     for device_id in ("child1", "child3", "child4"):
         assert device_registry.async_get_device(identifiers={(DOMAIN, device_id)})
+
+    # Add the previously removed child device
+    mock_device.children = [
+        children["child1"],
+        children["child2"],
+        children["child3"],
+        children["child4"],
+    ]
+    freezer.tick(5)
+    async_fire_time_changed(hass)
+
+    for child_id in (1, 2, 3, 4):
+        entity_id = f"{platform}.child_{child_id}_{translated_name}"
+        state = hass.states.get(entity_id)
+        assert state
+        assert entity_registry.async_get(entity_id)
+
+    for device_id in ("child1", "child2", "child3", "child4"):
+        assert device_registry.async_get_device(identifiers={(DOMAIN, device_id)})