From 2c731a0c1a11bb435697d6fc03f0ef3ff5c86eff Mon Sep 17 00:00:00 2001
From: Wei Ji <23487320+weiji14@users.noreply.github.com>
Date: Wed, 23 Jul 2025 13:56:08 +1200
Subject: [PATCH 1/2] Regression test to ensure gmt accessor info is kept after
 file deletion

Regression test based on code at https://github.com/GenericMappingTools/pygmt/issues/4005, checking that GMTDataArrayAccessor registration/gtype is preserved after temporary file is deleted.
---
 pygmt/tests/test_xarray_backend.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/pygmt/tests/test_xarray_backend.py b/pygmt/tests/test_xarray_backend.py
index a9244118c97..eed5a8bd45f 100644
--- a/pygmt/tests/test_xarray_backend.py
+++ b/pygmt/tests/test_xarray_backend.py
@@ -9,6 +9,7 @@
 import numpy.testing as npt
 import pytest
 import xarray as xr
+from pygmt.clib import Session
 from pygmt.enums import GridRegistration, GridType
 from pygmt.exceptions import GMTValueError
 from pygmt.helpers import GMTTempFile
@@ -38,6 +39,28 @@ def test_xarray_backend_load_dataarray():
         dataarray.to_netcdf(tmpfile.name)
 
 
+def test_xarray_backend_load_dataarray_temp_nc_grid():
+    """
+    Check that xarray.load_dataarray works to read a temporary netCDF grid, and ensure
+    that GMTDataArrayAccessor information is retained after original file is deleted.
+
+    This is a regression test for
+    https://github.com/GenericMappingTools/pygmt/issues/4005
+    """
+
+    with Session() as lib:
+        with GMTTempFile(suffix=".nc") as tmpfile:
+            args = f"@earth_relief_01d_g -T -G{tmpfile.name}"  # change from gridline to pixel registration
+            lib.call_module(module="grdedit", args=args)
+            dataarray = xr.load_dataarray(
+                tmpfile.name, engine="gmt", raster_kind="grid"
+            )
+
+        # Ensure GMTDataArrayAccessor info is preserved after tempfile is deleted
+        assert dataarray.gmt.registration is GridRegistration.PIXEL
+        assert dataarray.gmt.gtype is GridType.CARTESIAN
+
+
 def test_xarray_backend_gmt_open_nc_grid():
     """
     Ensure that passing engine='gmt' to xarray.open_dataarray works to open a netCDF

From 5ab6116cde63c9b920f74c8820cb5fb79daec823 Mon Sep 17 00:00:00 2001
From: Wei Ji <23487320+weiji14@users.noreply.github.com>
Date: Wed, 23 Jul 2025 14:49:31 +1200
Subject: [PATCH 2/2] Load GMTDataArray accessor information at xr.Dataset
 level

Need to load the gmt accessor at the xr.Dataset level instead of the xr.DataArray level, otherwise the info gets lost at the `.to_dataset()` call. Had to add the `@xr.register_dataset_accessor("gmt")` decorator on `class GMTDataArrayAccessort` to prevent `AttributeError: 'Dataset' object has no attribute 'gmt'`.
---
 pygmt/tests/test_xarray_backend.py | 6 +++++-
 pygmt/xarray/accessor.py           | 1 +
 pygmt/xarray/backend.py            | 4 +++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/pygmt/tests/test_xarray_backend.py b/pygmt/tests/test_xarray_backend.py
index eed5a8bd45f..d9f7d72c80a 100644
--- a/pygmt/tests/test_xarray_backend.py
+++ b/pygmt/tests/test_xarray_backend.py
@@ -50,7 +50,11 @@ def test_xarray_backend_load_dataarray_temp_nc_grid():
 
     with Session() as lib:
         with GMTTempFile(suffix=".nc") as tmpfile:
-            args = f"@earth_relief_01d_g -T -G{tmpfile.name}"  # change from gridline to pixel registration
+            args = [
+                "@earth_relief_01d_g",
+                "-T",  # change from gridline to pixel registration
+                f"-G{tmpfile.name}",
+            ]
             lib.call_module(module="grdedit", args=args)
             dataarray = xr.load_dataarray(
                 tmpfile.name, engine="gmt", raster_kind="grid"
diff --git a/pygmt/xarray/accessor.py b/pygmt/xarray/accessor.py
index 05e162ed78f..cf1d6d42be3 100644
--- a/pygmt/xarray/accessor.py
+++ b/pygmt/xarray/accessor.py
@@ -25,6 +25,7 @@
 
 
 @xr.register_dataarray_accessor("gmt")
+@xr.register_dataset_accessor("gmt")
 class GMTDataArrayAccessor:
     """
     GMT accessor for :class:`xarray.DataArray`.
diff --git a/pygmt/xarray/backend.py b/pygmt/xarray/backend.py
index 37500932b57..ceeee93ff10 100644
--- a/pygmt/xarray/backend.py
+++ b/pygmt/xarray/backend.py
@@ -150,4 +150,6 @@ def open_dataset(  # type: ignore[override]
                 raster.encoding["source"] = (
                     sorted(source)[0] if isinstance(source, list) else source
                 )
-                return raster.to_dataset()
+                raster_dataset: xr.Dataset = raster.to_dataset()
+                _ = raster_dataset.gmt  # Load GMTDataArray accessor information
+                return raster_dataset