If you call drush migrate:messages for a migration that has not yet run, a fatal error occurs:
TypeError: Drupal\migrate_tools\IdMapFilter::currentSource(): Return value must be of type array, null returned in Drupal\migrate_tools\IdMapFilter->currentSource() (line 216 of /var/www/app/docroot/modules/contrib/migrate_tools/src/IdMapFilter.php).
1. define a migration, e.g. mymigration
2. run drush migrate:messages mymigration
tbc
Fixed
6.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Change looks OK. Not sure if we also need to update comments and/or a test.
Automatically closed - issue fixed for 2 weeks with no activity.