Issue #2846002 by Jo Fitzgerald, joachim: Pipeline failure exceptions should...

Issue #2846002 by Jo Fitzgerald, joachim: Pipeline failure exceptions should say which plugin they failed at

core/modules/migrate/src/MigrateExecutable.php

@@ -358,7 +358,7 @@ public function processRow(Row $row, array $process = NULL, $value = NULL) {
         if ($multiple && !$definition['handle_multiples']) {
           $new_value = [];
           if (!is_array($value)) {
-            throw new MigrateException(sprintf('Pipeline failed for destination %s: %s got instead of an array,', $destination, $value));
+            throw new MigrateException(sprintf('Pipeline failed at %s plugin for destination %s: %s received instead of an array,', $plugin->getPluginId(), $destination, $value));
           }
           $break = FALSE;
           foreach ($value as $scalar_value) {

core/modules/migrate/tests/src/Unit/MigrateExecutableTest.php

@@ -3,6 +3,7 @@
 namespace Drupal\Tests\migrate\Unit;
 
 use Drupal\Component\Utility\Html;
+use Drupal\migrate\Plugin\MigrateProcessInterface;
 use Drupal\migrate\Plugin\MigrationInterface;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
 use Drupal\migrate\MigrateException;
@@ -419,6 +420,25 @@ public function testProcessRowEmptyPipeline() {
     $this->assertSame($row->getDestination(), []);
   }
 
+  /**
+   * Tests the processRow pipeline exception.
+   */
+  public function testProcessRowPipelineException() {
+    $row = new Row();
+    $plugin = $this->prophesize(MigrateProcessInterface::class);
+    $plugin->getPluginDefinition()->willReturn(['handle_multiples' => FALSE]);
+    $plugin->transform(NULL, $this->executable, $row, 'destination_id')
+      ->willReturn('transform_return_string');
+    $plugin->multiple()->willReturn(TRUE);
+    $plugin->getPluginId()->willReturn('plugin_id');
+    $plugin = $plugin->reveal();
+    $plugins['destination_id'] = [$plugin, $plugin];
+    $this->migration->method('getProcessPlugins')->willReturn($plugins);
+
+    $this->setExpectedException(MigrateException::class, 'Pipeline failed at plugin_id plugin for destination destination_id: transform_return_string received instead of an array,');
+    $this->executable->processRow($row);
+  }
+
   /**
    * Returns a mock migration source instance.
    *