Issue #3285637 by mikelutz, danflanagan8, benjifisher: 'Get' Process plugin should handle multiple

(cherry picked from commit 91baefec)

core/modules/migrate/src/Plugin/migrate/process/Get.php

@@ -88,7 +88,8 @@
  * @see \Drupal\migrate\Plugin\MigrateProcessInterface
  *
  * @MigrateProcessPlugin(
- *   id = "get"
+ *   id = "get",
+ *   handle_multiples = TRUE
  * )
  */
 class Get extends ProcessPluginBase {

core/modules/migrate/tests/src/Kernel/process/HandleMultiplesTest.php

@@ -71,6 +71,32 @@ public function getDefinition() {
             'delimiter' => '/',
           ],
         ],
+        // Process pipeline for testing 'get' overriding a single.
+        'get_from_single' => [
+          // Returns a string.
+          [
+            'plugin' => 'get',
+            'source' => 'scalar',
+          ],
+          // Ignore previous and return an array.
+          [
+            'plugin' => 'get',
+            'source' => 'multiple',
+          ],
+        ],
+        // Process pipeline for testing 'get' overriding an array.
+        'get_from_multiple' => [
+          // Returns an array.
+          [
+            'plugin' => 'get',
+            'source' => 'multiple',
+          ],
+          // Ignore previous and return a string.
+          [
+            'plugin' => 'get',
+            'source' => 'scalar',
+          ],
+        ],
       ],
       'destination' => [
         'plugin' => 'config',
@@ -131,6 +157,11 @@ public function scalarAndMultipleValuesProviderSource() {
             'BAR',
             'BAZ',
           ],
+          'get_from_single' => [
+            'foo',
+            'bar/baz',
+          ],
+          'get_from_multiple' => 'foo/bar',
         ],
       ],
     ];