Log a warning when replacing existing config entry with same unique id (#130567)

* Log a warning when replacing existing config entry with same unique id

* Exclude mobile_app

* Ignore custom integrations

* Apply suggestions from code review

* Apply suggestions from code review

* Update config_entries.py

* Fix handler

* Adjust and add tests

* Apply suggestions from code review

* Apply suggestions from code review

* Update comment

* Update config_entries.py

* Apply suggestions from code review

homeassistant/config_entries.py

@@ -1628,6 +1628,23 @@ class ConfigEntriesFlowManager(
                 result["handler"], flow.unique_id
             )
 
+        if existing_entry is not None and flow.handler != "mobile_app":
+            # This causes the old entry to be removed and replaced, when the flow
+            # should instead be aborted.
+            # In case of manual flows, integrations should implement options, reauth,
+            # reconfigure to allow the user to change settings.
+            # In case of non user visible flows, the integration should optionally
+            # update the existing entry before aborting.
+            # see https://developers.home-assistant.io/blog/2025/01/16/config-flow-unique-id/
+            report_usage(
+                "creates a config entry when another entry with the same unique ID "
+                "exists",
+                core_behavior=ReportBehavior.LOG,
+                core_integration_behavior=ReportBehavior.LOG,
+                custom_integration_behavior=ReportBehavior.LOG,
+                integration_domain=flow.handler,
+            )
+
         # Unload the entry before setting up the new one.
         if existing_entry is not None and existing_entry.state.recoverable:
             await self.config_entries.async_unload(existing_entry.entry_id)