Let grid attrs property return a deepcopy

tests/test_core_utils.py

@@ -53,7 +53,7 @@ def test_unique_grids():
     grid2 = grid1d()
     grid_different = grid1d()
 
-    grid_different.attrs["something"] = "different"
+    grid_different._attrs["something"] = "different"
 
     assert len(unique_grids([grid, grid2, grid_different])) == 2
     assert len(unique_grids([grid, grid2])) == 1

tests/test_ugrid1d.py

@@ -50,6 +50,13 @@ def test_ugrid1d_init():
     assert grid.node_y.flags["C_CONTIGUOUS"]
 
 
+def test_safe_attrs():
+    # .attrs should return a copy
+    grid = grid1d()
+    assert grid.attrs == grid.attrs
+    assert grid._attrs is not grid.attrs
+
+
 def test_ugrid1d_alternative_init():
     custom_attrs = {
         "node_dimension": "nNetNode",
@@ -466,7 +473,7 @@ def test_equals():
     assert grid.equals(grid_copy)
     xr_grid = grid.to_dataset()
     assert not grid.equals(xr_grid)
-    grid_copy.attrs["attr"] = "something_else"
+    grid_copy._attrs["attr"] = "something_else"
     # Dataset.identical is called so returns False
     assert not grid.equals(grid_copy)
 

tests/test_ugrid2d.py

@@ -107,6 +107,13 @@ def test_ugrid2d_init():
     assert grid._face_edge_connectivity is None
 
 
+def test_safe_attrs():
+    # .attrs should return a copy
+    grid = grid2d()
+    assert grid.attrs == grid.attrs
+    assert grid._attrs is not grid.attrs
+
+
 def test_ugrid2d_alternative_init():
     custom_attrs = {
         "node_dimension": "nNetNode",
@@ -1448,7 +1455,7 @@ def test_equals():
     assert grid.equals(grid_copy)
     xr_grid = grid.to_dataset()
     assert not grid.equals(xr_grid)
-    grid_copy.attrs["attr"] = "something_else"
+    grid_copy._attrs["attr"] = "something_else"
     assert not grid.equals(grid_copy)
 
 

xugrid/ugrid/ugridbase.py

@@ -322,7 +322,7 @@ def copy(self):
 
     @property
     def attrs(self):
-        return self._attrs
+        return copy.deepcopy(self._attrs)
 
     @property
     def node_dimension(self):