Issue #3068584 by Matroskeen, jhchnc, gapple, azussman: item_selector failing...

Issue #3068584 by Matroskeen, jhchnc, gapple, azussman: item_selector failing to grab a inner level JSON array

tests/data/item_selector.json

@@ -3,11 +3,27 @@
   "data": [
     {
       "id": 1,
-      "title": "1 item"
+      "title": "1 item",
+      "items": [
+        {
+          "id": 1,
+          "title": "1.1 item"
+        },
+        {
+          "id": 2,
+          "title": "1.2 item"
+        }
+      ]
     },
     {
       "id": 2,
-      "title": "2 item"
+      "title": "2 item",
+      "items": [
+        {
+          "id": 3,
+          "title": "2.1 item"
+        }
+      ]
     }
   ],
   "data_empty": [],

tests/src/Kernel/Plugin/migrate_plus/data_parser/JsonTest.php

@@ -213,6 +213,38 @@ final class JsonTest extends KernelTestBase {
           ],
         ],
       ],
+      'item_selector 2nd level' => [
+        'item_selector' => '/data/0/items',
+        'fields' => $fields,
+        'expected' => [
+          [
+            'id' => '1',
+            'title' => '1.1 item',
+          ],
+          [
+            'id' => '2',
+            'title' => '1.2 item',
+          ],
+        ],
+      ],
+      'item_selector 2nd level, depth selector' => [
+        'item_selector' => 3,
+        'fields' => $fields,
+        'expected' => [
+          [
+            'id' => '1',
+            'title' => '1.1 item',
+          ],
+          [
+            'id' => '2',
+            'title' => '1.2 item',
+          ],
+          [
+            'id' => '3',
+            'title' => '2.1 item',
+          ],
+        ],
+      ],
     ];
   }