Fix serialization of VolMesh cell attributes

AUTHORS.md

@@ -46,3 +46,4 @@
 - Eric Gozzi <<eric.gozzi@arch.ethz.ch>> [@ericgozzi](https://github.com/ericgozzi)
 - Daniel Nunes Locatelli <<nuneslocatelli@arch.ethz.ch>> [@daniel-locatelli](https://github.com/daniel-locatelli)
 - Mengxi He <<m.he@lekolabs.com>> [@mengxihex](https://github.com/mengxihex)
+- Arian Moeini <<arianmoeini11@gmail.com>> [@ArianMoeini](https://github.com/ArianMoeini)

src/compas/datastructures/volmesh/volmesh.py

@@ -170,7 +170,7 @@ def __data__(self):
             "cell": {str(cell): faces for cell, faces in _cell.items()},
             "edge_data": self._edge_data,
             "face_data": self._face_data,
-            "cell_data": {str(cell): attr for cell, attr in self._cell_data},
+            "cell_data": {str(cell): attr for cell, attr in self._cell_data.items()},
             "max_vertex": self._max_vertex,
             "max_face": self._max_face,
             "max_cell": self._max_cell,

tests/compas/datastructures/test_volmesh.py

@@ -60,6 +60,18 @@ def test_volmesh_data():
         assert VolMesh.validate_data(other.__data__)
 
 
+def test_volmesh_cell_attributes_survive_json_roundtrip(halfface):
+    cells = list(halfface.cells())
+    halfface.cell_attribute(cells[0], "material", "mycelium")
+    halfface.cell_attribute(cells[-1], "density", 0.5)
+
+    restored = compas.json_loads(compas.json_dumps(halfface))
+
+    assert restored.cell_attribute(cells[0], "material") == "mycelium"
+    assert restored.cell_attribute(cells[-1], "density") == 0.5
+    assert restored.__data__["cell_data"] == halfface.__data__["cell_data"]
+
+
 # ==============================================================================
 # Builders
 # ==============================================================================