wp-admin/includes/class-wp-importer.php:253Replaces newlines, tabs, and multiple spaces with a single space.
$textstringstring public function min_whitespace( $text ) { return preg_replace( '|[\r\n\t ]+|', ' ', $text ); }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-wp-importer.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.