Emit DC_EVENT_ACCOUNTS_BACKGROUND_FETCH_DONE even on timeout

Otherwise if there is a timeout,
UI will wait for DC_EVENT_ACCOUNTS_BACKGROUND_FETCH_DONE forever.

deltachat-ffi/deltachat.h

@@ -3157,15 +3157,14 @@ void           dc_accounts_maybe_network_lost    (dc_accounts_t* accounts);
  *
  * dc_accounts_background_fetch() was created for the iOS Background fetch.
  *
- * The `DC_EVENT_ACCOUNTS_BACKGROUND_FETCH_DONE` event is emitted at the end,
- * process all events until you get this one and you can safely return to the background
+ * The `DC_EVENT_ACCOUNTS_BACKGROUND_FETCH_DONE` event is emitted at the end
+ * even in case of timeout, unless the function fails and returns 0.
+ * Process all events until you get this one and you can safely return to the background
  * without forgetting to create notifications caused by timing race conditions.
  *
  * @memberof dc_accounts_t
  * @param timeout The timeout in seconds
- * @return Return 1 on success and 0 on failure (like timeout)
- *    But note that this only indicates that the fetch of all accounts was done before the timeout.
- *    To know whether it worked you need to look for the events.
+ * @return Return 1 if DC_EVENT_ACCOUNTS_BACKGROUND_FETCH_DONE was emitted and 0 otherwise.
  */
 int            dc_accounts_background_fetch    (dc_accounts_t* accounts, uint64_t timeout);
 

deltachat-jsonrpc/src/api.rs

@@ -233,8 +233,9 @@ impl CommandApi {
 
     /// Performs a background fetch for all accounts in parallel with a timeout.
     ///
-    /// The `AccountsBackgroundFetchDone` event is emitted at the end,
-    /// process all events until you get this one and you can safely return to the background
+    /// The `AccountsBackgroundFetchDone` event is emitted at the end
+    /// if the method returns sucessfully, even in case of timeout.
+    /// Process all events until you get this one and you can safely return to the background
     /// without forgetting to create notifications caused by timing race conditions.
     async fn accounts_background_fetch(&self, timeout_in_seconds: f64) -> Result<()> {
         self.accounts

src/accounts.rs

@@ -317,10 +317,18 @@ impl Accounts {
     /// The `AccountsBackgroundFetchDone` event is emitted at the end,
     /// process all events until you get this one and you can safely return to the background
     /// without forgetting to create notifications caused by timing race conditions.
+    ///
+    /// On error no `AccountsBackgroundFetchDone` event is emitted.
     pub async fn background_fetch(&self, timeout: std::time::Duration) -> Result<()> {
-        let result = tokio::time::timeout(timeout, self.background_fetch_without_timeout()).await;
+        if let Err(_err) =
+            tokio::time::timeout(timeout, self.background_fetch_without_timeout()).await
+        {
+            self.emit_event(EventType::Warning(
+                "Background fetch timed out.".to_string(),
+            ));
+        }
         self.emit_event(EventType::AccountsBackgroundFetchDone);
-        result.map_err(|err| err.into())
+        Ok(())
     }
 
     /// Emits a single event.