[bluetooth] Fix disappearing bluetooth devices in Inbox (#10187)

* [bluetooth] Notify things again when they are removed from listeners like Inbox
* [bluetooth] Add javadoc on retractDiscoveryResult()

Signed-off-by: Peter Rosenberg <prosenb.dev@gmail.com>

bundles/org.openhab.binding.bluetooth/src/main/java/org/openhab/binding/bluetooth/discovery/internal/BluetoothDiscoveryService.java

@@ -133,6 +133,13 @@ public void stopScan() {
  for (BluetoothAdapter adapter : adapters) {
  adapter.scanStop();
  }
+
+ // The method `removeOlderResults()` removes the Things from listeners like `Inbox`.
+ // We therefore need to reset `latestSnapshot` so that the Things are notified again next time.
+ // Results newer than `getTimestampOfLastScan()` will also be notified again but do not lead to duplicates.
+ discoveryCaches.values().forEach(discoveryCache -> {
+ discoveryCache.latestSnapshot.putValue(null);
+ });
  removeOlderResults(getTimestampOfLastScan());
  }
 
@@ -290,6 +297,12 @@ private void publishDiscoveryResult(BluetoothAdapter adapter, DiscoveryResult re
  discoveryResults.put(adapter, results);
  }
 
+ /**
+ * Called when a new discovery is published and thus requires the old discovery to be removed first.
+ *
+ * @param adapter to get the results to be removed
+ * @param result unused
+ */
  private void retractDiscoveryResult(BluetoothAdapter adapter, DiscoveryResult result) {
  Set<DiscoveryResult> results = discoveryResults.remove(adapter);
  if (results != null) {