PropertyModifierHook: allow to clone rows

fixes #2060

library/Director/Hook/PropertyModifierHook.php

@@ -59,6 +59,21 @@ abstract class PropertyModifierHook
         return false;
     }
 
+    /**
+     * This creates one cloned row for every entry of the result array
+     *
+     * When set to true and given that the property modifier returns an Array,
+     * the current row will be cloned for every entry of that array. The modified
+     * property will then be replace each time accordingly. An empty Array
+     * completely removes the corrent row.
+     *
+     * @return bool
+     */
+    public function expandsRows()
+    {
+        return false;
+    }
+
     /**
      * Reject this whole row
      *

library/Director/Objects/ImportSource.php

@@ -307,22 +307,38 @@ class ImportSource extends DbObjectWithSettings implements ExportInterface
             return $this;
         }
 
-
         foreach ($modifiers as $modPair) {
             /** @var PropertyModifierHook $modifier */
             list($property, $modifier) = $modPair;
             $rejected = [];
+            $newRows = [];
             foreach ($data as $key => $row) {
                 $this->applyPropertyModifierToRow($modifier, $property, $row);
                 if ($modifier->rejectsRow()) {
                     $rejected[] = $key;
                     $modifier->rejectRow(false);
                 }
+                if ($modifier->expandsRows()) {
+                    $target = $modifier->getTargetProperty($property);
+
+                    $newValue = $row->$target;
+                    if (\is_array($newValue)) {
+                        foreach ($newValue as $val) {
+                            $newRow = clone $row;
+                            $newRow->$target = $val;
+                            $newRows[] = $newRow;
+                        }
+                        $rejected[] = $key;
+                    }
+                }
             }
 
             foreach ($rejected as $key) {
                 unset($data[$key]);
             }
+            foreach ($newRows as $row) {
+                $data[] = $row;
+            }
         }
 
         return $this;