Issue #3142893 by hchonov, Raunak.singh, kishor_kolekar, alexpott, ts…

…toeckler, catch, kfritsche, johnwebdev: Memory leak - typed data prototypes for field items are not re-used like intended

(cherry picked from commit ce5d85281b53bb683c6e0c9cdd27a14368584091)

lib/Drupal/Core/TypedData/TypedDataManager.php

@@ -169,7 +169,15 @@ public function getPropertyInstance(TypedDataInterface $object, $property_name,
       $parts[] = json_encode($settings);
     }
     // Property path for the requested data object.
-    $parts[] = $object->getPropertyPath() . '.' . $property_name;
+    $parts[] = $object->getPropertyPath();
+    // Only property instances of complex data types should be cached by the
+    // property name, as they represent different properties. Properties of list
+    // data types are the items of the list and the property name represents
+    // only the delta in that list and not an unique property, which is why all
+    // items should use the same prototype.
+    if ($object instanceof ComplexDataInterface) {
+      $parts[] = $property_name;
+    }
     $key = implode(':', $parts);
 
     // Create the prototype if needed.