Ensure weight_windows_file information is read from XML (#3587)

Co-authored-by: Paul Romano <[email protected]>

Author: yrrepy

openmc/settings.py

@@ -1641,6 +1641,7 @@ def _create_weight_windows_subelement(self, root, mesh_memo=None):
                 if mesh_memo is not None:
                     mesh_memo.add(ww.mesh.id)
 
+    def _create_weight_windows_on_subelement(self, root):
         if self._weight_windows_on is not None:
             elem = ET.SubElement(root, "weight_windows_on")
             elem.text = str(self._weight_windows_on).lower()
@@ -2074,10 +2075,16 @@ def _weight_windows_from_xml_element(self, root, meshes=None):
             ww = WeightWindows.from_xml_element(elem, meshes)
             self.weight_windows.append(ww)
 
+    def _weight_windows_on_from_xml_element(self, root):
         text = get_text(root, 'weight_windows_on')
         if text is not None:
             self.weight_windows_on = text in ('true', '1')
 
+    def _weight_windows_file_from_xml_element(self, root):
+        text = get_text(root, 'weight_windows_file')
+        if text is not None:
+            self.weight_windows_file = text
+
     def _weight_window_checkpoints_from_xml_element(self, root):
         elem = root.find('weight_window_checkpoints')
         if elem is None:
@@ -2214,6 +2221,7 @@ def to_xml_element(self, mesh_memo=None):
         self._create_log_grid_bins_subelement(element)
         self._create_write_initial_source_subelement(element)
         self._create_weight_windows_subelement(element, mesh_memo)
+        self._create_weight_windows_on_subelement(element)
         self._create_weight_window_generators_subelement(element, mesh_memo)
         self._create_weight_windows_file_element(element)
         self._create_weight_window_checkpoints_subelement(element)
@@ -2324,6 +2332,8 @@ def from_xml_element(cls, elem, meshes=None):
         settings._log_grid_bins_from_xml_element(elem)
         settings._write_initial_source_from_xml_element(elem)
         settings._weight_windows_from_xml_element(elem, meshes)
+        settings._weight_windows_on_from_xml_element(elem)
+        settings._weight_windows_file_from_xml_element(elem)
         settings._weight_window_generators_from_xml_element(elem, meshes)
         settings._weight_window_checkpoints_from_xml_element(elem)
         settings._max_history_splits_from_xml_element(elem)