Make illegal path-like variable names when constructing a DataTree from a Dataset

datatree/datatree.py

@@ -103,6 +103,18 @@ def _check_for_name_collisions(
         )
 
 
+def _check_for_slashes_in_names(variables: Iterable[Hashable]) -> None:
+    offending_variable_names = [
+        name for name in variables if isinstance(name, str) and "/" in name
+    ]
+    if len(offending_variable_names) > 0:
+        raise KeyError(
+            f"Given Dataset contains path-like variable names: {offending_variable_names}. "
+            "A Dataset represents a group, and a single group "
+            "cannot have path-like variable names. "
+        )
+
+
 class DatasetView(Dataset):
     """
     An immutable Dataset-like view onto the data in a single DataTree node.
@@ -401,6 +413,7 @@ def __init__(
             children = {}
         ds = _coerce_to_dataset(data)
         _check_for_name_collisions(children, ds.variables)
+        _check_for_slashes_in_names(ds.variables)
 
         super().__init__(name=name)
 

datatree/tests/test_datatree.py

@@ -1,3 +1,4 @@
+import re
 from copy import copy, deepcopy
 
 import numpy as np
@@ -68,6 +69,23 @@ def test_child_gets_named_on_attach(self):
         mary = DataTree(children={"Sue": sue})  # noqa
         assert sue.name == "Sue"
 
+    def test_dataset_containing_slashes(self):
+        xda = xr.DataArray(
+            [[1, 2]],
+            coords={"label": ["a"], "R30m/y": [30, 60]},
+        )
+        xds = xr.Dataset({"group/subgroup/my_variable": xda})
+        with pytest.raises(
+            KeyError,
+            match=re.escape(
+                "Given Dataset contains path-like variable names: "
+                "['R30m/y', 'group/subgroup/my_variable']. "
+                "A Dataset represents a group, and a single group cannot "
+                "have path-like variable names. "
+            ),
+        ):
+            DataTree(xds)
+
 
 class TestPaths:
     def test_path_property(self):

docs/source/whats-new.rst

@@ -45,6 +45,10 @@ Deprecations
 
 Bug fixes
 ~~~~~~~~~
+
+- Make illegal path-like variable names when constructing a DataTree from a Dataset
+  (:issue:`311`, :pull:`314`)
+  By `Etienne Schalk <https://github.com/etienneschalk>`_.
 - Keep attributes on nodes containing no data in :py:func:`map_over_subtree`. (:issue:`278`, :pull:`279`)
   By `Sam Levang <https://github.com/slevang>`_.