Notice: Undefined variable: label in _batch_process()

A bit confused about the difference between $task_message and $label in this function, as they appear to basically be the same thing? It feels like this whole function needs a refactor as it is quite confusing to follow.

But, this is a simple fix, so RTBC.

As we're not adding a test I'd rather do something that eliminates the $label. It is essential useless. We could initialise $task_message outside the first while loop and re-initialise it in the loop too and that way we can remove label and have no conditionality to test.

Also an update to the _batch_process return value would be great so we know what this is and that it should be there.

+++ b/core/includes/batch.inc
@@ -276,7 +277,6 @@ function _batch_process() {
-    $task_message = $label = '';

I'm not sure that this removal is correct - I think the purposed is to reinitialize the variable for each loop. I'd leave $task_message = ''; otherwise we'll be changing the inputs to

      // Build the 'context' array and execute the function call.
      $batch_context = [
        'sandbox'  => &$current_set['sandbox'],
        'results'  => &$current_set['results'],
        'finished' => &$finished,
        'message'  => &$task_message,
      ];
      call_user_func_array($callback, array_merge($args, [&$batch_context]));

We still need to initialise it outside the loop, in case the loop is never entered.

Thanks for update. Updated the correct patch with variable initialized out of loop.

#11 looks good, thanks.

Committed f159bbd and pushed to 8.7.x. Thanks!