Add implicit complement name to DAGMC cell durin sync DAGMC universes

Author: pshriwise

openmc/dagmc.py

@@ -623,7 +623,13 @@ def sync_dagmc_cells(self, mats: Iterable[openmc.Material]):
                 fill = [mats_per_id[mat.id] for mat in dag_cell.fill if mat]
             else:
                 fill = mats_per_id[dag_cell.fill.id] if dag_cell.fill else None
-            self.add_cell(openmc.DAGMCCell(cell_id=dag_cell_id, fill=fill))
+            name = dag_cell.name
+            if dag_cell_id in self._cells:
+                self._cells[dag_cell_id].name = name
+                self._cells[dag_cell_id].fill = fill
+            else:
+                self.add_cell(
+                    openmc.DAGMCCell(cell_id=dag_cell_id, name=name, fill=fill))
 
     @add_plot_params
     def plot(self, *args, **kwargs):

src/dagmc.cpp

@@ -282,6 +282,9 @@ void DAGUniverse::init_geometry(const MaterialOverrides& material_overrides,
                : dagmc_instance_->id_by_index(3, c->dag_index());
     c->universe_ = this->id_;
     c->fill_ = C_NONE; // no fill, single universe
+    if (dagmc_instance_->is_implicit_complement(vol_handle)) {
+      c->name_ = "implicit complement";
+    }
 
     auto in_map = model::cell_map.find(c->id_);
     if (in_map == model::cell_map.end()) {

tests/unit_tests/dagmc/test_model.py

@@ -94,6 +94,22 @@ def test_dagmc_replace_material_assignment(model):
             assert univ.cells[cell_id].fill == mats["foo"]
 
 
+def test_dagmc_sync_cell_names(model):
+    dag_univ = None
+    for univ in model.geometry.get_all_universes().values():
+        if isinstance(univ, openmc.DAGMCUniverse):
+            dag_univ = univ
+            break
+
+    assert dag_univ is not None
+
+    for cell_id, cell in dag_univ.cells.items():
+        assert cell.name == openmc.lib.cells[cell_id].name
+
+    assert any(cell.name == "implicit complement"
+               for cell in dag_univ.cells.values())
+
+
 def test_dagmc_add_material_override_with_id(model):
     mats = {}
     mats["foo"] = openmc.Material(name="foo")