drush_backend_batch_process() should clear batch_get()

[pfrenssen]

Describe the bug
This is coming out of a bug report that was filed for Search API: Issue #3011340: Multiple index update causes drush config import to get stuck.

If a batch operation is added with batch_set() and then processed using drush_backend_batch_process() then the list of batch operations is not cleared. If a second call to drush_backend_batch_process() is made in the same request, then the original set of batch operations is requeued, leading to unexpected results.

To Reproduce

// Define a batch operation.
$batch_definition = [
  'operations' => [[[$this, 'processBatch'], [$task_ids, $conditions]]],
];
batch_set($batch_definition);

// This call will execute the batch operation.
drush_backend_batch_process();

// Define a second batch operation.
$batch_definition = [
  'operations' => [[[$this, 'processBatch'], [$task_ids, $conditions]]],
];
batch_set($batch_definition);

// This call will execute both the first and the second batch operation.
// Since the first one has already been processed this might cause unexpected results.
drush_backend_batch_process();

Expected behavior
drush_backend_batch_process() should clean up batch_get() after it is done.

Workaround

$result = drush_backend_batch_process();
if ($result['context']['drush_batch_process_finished'] === TRUE) {
  $batch = &batch_get();
  $batch = NULL;
}

System Configuration

Q	A
Drush version?	master
Drupal version?	8.x-dev
PHP version	7.2
OS?	Linux

[weitzman]

I guess the code below is not sufficient? If we need more code tahts probably where it should go

drush/includes/batch.inc

Lines 345 to 349 in eaf9c3e

	if (drush_drupal_major_version() >= 8) {
	/** @var \Drupal\Core\Batch\BatchStorage $batch_storage */
	$batch_storage = \Drupal::service('batch.storage');
	$batch_storage->delete($batch['id']);
	}

[batkor]

subscribe
Thanks @pfrenssen

[lpeabody]

Just wanted to include this as a potentially related issue https://www.drupal.org/node/3068196, piggybacked from https://www.drupal.org/project/search_api/issues/3019652#comment-13167514. It provides additional context around the discussion @pfrenssen posted in the description.

[plach79]

Posted a PR implementing @pfrenssen's suggestion at #4886

[plach79]

For reference I discovered this while testing a fix for https://www.drupal.org/project/user_email_verification/issues/3245192.

[weitzman]

Fixed in #4886