From ec40e004861dac9c1f6019cd6447a19c87f709d1 Mon Sep 17 00:00:00 2001
From: Sam Evans <47793072+Sevans711@users.noreply.github.com>
Date: Mon, 10 Aug 2026 16:15:43 -0400
Subject: [PATCH] fix crash from getting healpix grid node_lat first

(also adds regression test. See #1637)
---
 test/io/test_healpix.py | 14 ++++++++++++++
 uxarray/grid/grid.py    |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/test/io/test_healpix.py b/test/io/test_healpix.py
index 947ccee79..84a359f97 100644
--- a/test/io/test_healpix.py
+++ b/test/io/test_healpix.py
@@ -280,3 +280,17 @@ def test_healpix_round_trip_consistency(tmp_path):
     # Validate grid dimensions are preserved
     assert reloaded_ugrid.n_face == original_grid.n_face
     assert reloaded_exodus.n_face == original_grid.n_face
+
+def test_healpix_grid_attr_access_order():
+    """Ensure can access node_lon & node_lat attributes of healpix grid in any order.
+    (If problem turns out to exists with other attributes, can add them here later.)
+    Regression test for #1637.
+    """
+    grid = ux.Grid.from_healpix(zoom=1)
+    grid.node_lon
+    grid.node_lat
+
+    # just making sure this doesn't crash:
+    grid = ux.Grid.from_healpix(zoom=1)
+    grid.node_lat
+    grid.node_lon
diff --git a/uxarray/grid/grid.py b/uxarray/grid/grid.py
index 3c86890f2..89643feb7 100644
--- a/uxarray/grid/grid.py
+++ b/uxarray/grid/grid.py
@@ -1002,7 +1002,7 @@ def node_lat(self) -> xr.DataArray:
         """
         if "node_lat" not in self._ds:
             if self.source_grid_spec == "HEALPix":
-                _populate_healpix_boundaries(self)
+                _populate_healpix_boundaries(self._ds)
             else:
                 _set_desired_longitude_range(self)
                 _populate_node_latlon(self)