Blog post for new helpers in reauth and reconfigure flows (#2356)

* New helpers and best practises for reauth and reconfigure flows

* Update and rename 2024-10-08-reauth-reconfigure-helpers.md to 2024-10-17-reauth-reconfigure-helpers.md

* Update config_entries_config_flow_handler.md

* Update config_entries_config_flow_handler.md

* Rename 2024-10-17-reauth-reconfigure-helpers.md to 2024-10-21-reauth-reconfigure-helpers.md

* Update 2024-10-21-reauth-reconfigure-helpers.md

* Apply suggestions from code review

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

---------

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

blog/2024-10-21-reauth-reconfigure-helpers.md

@@ -0,0 +1,21 @@
+---
+author: epenet
+authorURL: https://github.com/epenet
+title: "New helpers and best practises for reauth and reconfigure flows"
+---
+
+New helper methods have been added to the ConfigFlow to facilitate management of reauth and reconfigure flows:
+- `self._get_reauth_entry()` and `self._get_reconfigure_entry()` give access at any time to the corresponding config entry
+  - these should be used over `self.hass.config_entries.async_get_entry(self.context["entry_id"])`
+  - the config entry should be requested when needed (local variable, once per step) and not cached as class attributes
+  - if the steps are shared with discovery or user flows, `self.source` should be checked against `SOURCE_REAUTH` and `SOURCE_RECONFIGURE` before accessing the entry
+- `self._abort_if_unique_id_mismatch` allows you to abort if the `unique_id` does not match the `unique_id` of the config entry to reauthenticate or reconfigure
+  - this should be used after a call to `self.async_set_unique_id`
+  - if the steps are shared with discovery or user flows, `self.source` should be checked against `SOURCE_REAUTH` and `SOURCE_RECONFIGURE`
+  - other sources should continue to use `self._abort_if_unique_id_configured`
+- `self.async_update_reload_and_abort` has been adjusted to update the default message for reconfigure flows
+  - the new message `reconfigure_successful` must be present in `strings.json`
+- `self.async_update_reload_and_abort` has a new argument `data_updates` to merge the data updates with the pre-existing data
+  - this is preferred over the `data` argument, as it reduces the risk of data loss if the schema is updated
+
+More details can be found in the [reconfigure](/docs/config_entries_config_flow_handler#reconfigure) and [reauthentication](/docs/config_entries_config_flow_handler#reauthentication) documentation.

docs/config_entries_config_flow_handler.md

@@ -284,9 +284,11 @@ class ExampleConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
     async def async_step_reconfigure(self, user_input: dict[str, Any] | None = None):
         if user_input is not None:
             # TODO: process user input
+            self.async_set_unique_id(user_id)
+            self._abort_if_unique_id_mismatch()
             return self.async_update_reload_and_abort(
-                self._get_reauth_entry(),
-                data=data,
+                self._get_reconfigure_entry(),
+                data_updates=data,
             )
 
         return self.async_show_form(
@@ -360,11 +362,14 @@ class OAuth2FlowHandler(
 
     async def async_oauth_create_entry(self, data: dict) -> dict:
         """Create an oauth config entry or update existing entry for reauth."""
+        self.async_set_unique_id(user_id)
         if self.source == SOURCE_REAUTH:
+            self._abort_if_unique_id_mismatch()
             return self.async_update_reload_and_abort(
                 self._get_reauth_entry(),
-                data=data,
+                data_updates=data,
             )
+        self._abort_if_unique_id_configured()
         return await super().async_oauth_create_entry(data)
 ```