Issue #2599152 by mikeryan, jhedstrom: ROLLBACK_PRESERVE is not respected

core/modules/migrate/src/MigrateExecutable.php

@@ -330,11 +330,14 @@ class MigrateExecutable implements MigrateExecutableInterface {
     foreach ($id_map as $map_row) {
       $destination_key = $id_map->currentDestination();
       if ($destination_key) {
-        $this->getEventDispatcher()
-          ->dispatch(MigrateEvents::PRE_ROW_DELETE, new MigrateRowDeleteEvent($this->migration, $destination_key));
-        $destination->rollback($destination_key);
-        $this->getEventDispatcher()
-          ->dispatch(MigrateEvents::POST_ROW_DELETE, new MigrateRowDeleteEvent($this->migration, $destination_key));
+        $map_row = $id_map->getRowByDestination($destination_key);
+        if ($map_row['rollback_action'] == MigrateIdMapInterface::ROLLBACK_DELETE) {
+          $this->getEventDispatcher()
+            ->dispatch(MigrateEvents::PRE_ROW_DELETE, new MigrateRowDeleteEvent($this->migration, $destination_key));
+          $destination->rollback($destination_key);
+          $this->getEventDispatcher()
+            ->dispatch(MigrateEvents::POST_ROW_DELETE, new MigrateRowDeleteEvent($this->migration, $destination_key));
+        }
         // We're now done with this row, so remove it from the map.
         $id_map->deleteDestination($destination_key);
       }

core/modules/migrate/src/Tests/MigrateRollbackTest.php

@@ -9,6 +9,8 @@ namespace Drupal\migrate\Tests;
 
 use Drupal\migrate\Entity\Migration;
 use Drupal\migrate\MigrateExecutable;
+use Drupal\migrate\Plugin\MigrateIdMapInterface;
+use Drupal\migrate\Row;
 use Drupal\taxonomy\Entity\Term;
 use Drupal\taxonomy\Entity\Vocabulary;
 
@@ -112,6 +114,12 @@ class MigrateRollbackTest extends MigrateTestBase {
     // Import and validate term entities were created.
     $term_executable = new MigrateExecutable($term_migration, $this);
     $term_executable->import();
+    // Mark one row to be preserved on rollback.
+    $preserved_term_id = 2;
+    $map_row = $term_id_map->getRowBySource(['id' => $preserved_term_id]);
+    $dummy_row = new Row(['id' => $preserved_term_id], $ids);
+    $term_id_map->saveIdMapping($dummy_row, [$map_row['destid1']],
+      $map_row['source_row_status'], MigrateIdMapInterface::ROLLBACK_PRESERVE);
     foreach ($term_data_rows as $row) {
       /** @var Term $term */
       $term = Term::load($row['id']);
@@ -124,7 +132,12 @@ class MigrateRollbackTest extends MigrateTestBase {
     $term_executable->rollback();
     foreach ($term_data_rows as $row) {
       $term = Term::load($row['id']);
-      $this->assertNull($term);
+      if ($row['id'] == $preserved_term_id) {
+        $this->assertNotNull($term);
+      }
+      else {
+        $this->assertNull($term);
+      }
       $map_row = $term_id_map->getRowBySource(['id' => $row['id']]);
       $this->assertFalse($map_row);
     }