fix indexing error due to inproper filter of None slices

Author: philipc2

docs/user-guide/subset.ipynb

@@ -20,18 +20,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
    "metadata": {
-    "ExecuteTime": {
-     "end_time": "2025-08-06T02:06:43.989811Z",
-     "start_time": "2025-08-06T02:06:43.930068Z"
-    },
     "collapsed": false,
     "jupyter": {
      "outputs_hidden": false
+    },
+    "ExecuteTime": {
+     "end_time": "2025-09-15T15:36:11.058925Z",
+     "start_time": "2025-09-15T15:36:10.649951Z"
     }
    },
-   "outputs": [],
    "source": [
     "import warnings\n",
     "\n",
@@ -45,7 +43,21 @@
     "plot_opts = {\"width\": 700, \"height\": 350}\n",
     "hv.extension(\"bokeh\")\n",
     "warnings.filterwarnings(\"ignore\")"
-   ]
+   ],
+   "outputs": [
+    {
+     "ename": "ModuleNotFoundError",
+     "evalue": "No module named 'geocat'",
+     "output_type": "error",
+     "traceback": [
+      "\u001B[31m---------------------------------------------------------------------------\u001B[39m",
+      "\u001B[31mModuleNotFoundError\u001B[39m                       Traceback (most recent call last)",
+      "\u001B[36mCell\u001B[39m\u001B[36m \u001B[39m\u001B[32mIn[1]\u001B[39m\u001B[32m, line 4\u001B[39m\n\u001B[32m      1\u001B[39m \u001B[38;5;28;01mimport\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mwarnings\u001B[39;00m\n\u001B[32m      3\u001B[39m \u001B[38;5;28;01mimport\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mcartopy\u001B[39;00m\u001B[34;01m.\u001B[39;00m\u001B[34;01mcrs\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[38;5;28;01mas\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mccrs\u001B[39;00m\n\u001B[32m----> \u001B[39m\u001B[32m4\u001B[39m \u001B[38;5;28;01mimport\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mgeocat\u001B[39;00m\u001B[34;01m.\u001B[39;00m\u001B[34;01mdatafiles\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[38;5;28;01mas\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mgeodf\u001B[39;00m\n\u001B[32m      5\u001B[39m \u001B[38;5;28;01mimport\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mgeoviews\u001B[39;00m\u001B[34;01m.\u001B[39;00m\u001B[34;01mfeature\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[38;5;28;01mas\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mgf\u001B[39;00m\n\u001B[32m      6\u001B[39m \u001B[38;5;28;01mimport\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mholoviews\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[38;5;28;01mas\u001B[39;00m\u001B[38;5;250m \u001B[39m\u001B[34;01mhv\u001B[39;00m\n",
+      "\u001B[31mModuleNotFoundError\u001B[39m: No module named 'geocat'"
+     ]
+    }
+   ],
+   "execution_count": 1
   },
   {
    "cell_type": "markdown",

pyproject.toml

@@ -76,6 +76,7 @@ extend-exclude = ["test","benchmarks"]
 
 [tool.ruff.lint]
 extend-select = ["I"]
+extend-ignore = ["E731"]
 
 [tool.ruff.lint.isort]
 known-first-party = ["uxarray"]

test/core/test_inheritance.py

@@ -211,3 +211,14 @@ def test_isel_non_grid_dim(self, ds):
 
         assert ds_t_multi.uxgrid == ds.uxgrid
         assert ds_t_multi.sizes['time'] == 2
+
+    def test_subscription(self, ds):
+
+        # index time dimension
+        res_t = ds['fc'][0]
+
+        assert isinstance(res_t, ux.UxDataArray)
+
+        # index grid dimension
+        res_f = ds['fc'][:, 0]
+        assert isinstance(res_f, ux.UxDataArray)

uxarray/core/utils.py

@@ -87,8 +87,22 @@ def _validate_indexers(indexers, indexers_kwargs, func_name, ignore_grid):
 
     from uxarray.constants import GRID_DIMS
 
+    # Used to filter out slices containing all Nones (causes subscription errors, i.e., var[0])
+    _is_full_none_slice = (
+        lambda v: isinstance(v, slice)
+        and v.start is None
+        and v.stop is None
+        and v.step is None
+    )
+
     indexers = either_dict_or_kwargs(indexers, indexers_kwargs, func_name)
-    grid_dims = set(GRID_DIMS).intersection(indexers)
+
+    # Only count a grid dim if its indexer is NOT a no-op full slice
+    grid_dims = {
+        dim
+        for dim in GRID_DIMS
+        if dim in indexers and not _is_full_none_slice(indexers[dim])
+    }
 
     if not ignore_grid and len(grid_dims) > 1:
         raise ValueError(