Merge pull request #4212 from meeseeksmachine/auto-backport-of-pr-421…

…1-on-yt-4.1.x

Backport PR #4211 on branch yt-4.1.x ([bugfix] H nuclei are being double-counted in the Arepo frontend)

yt/frontends/arepo/fields.py

@@ -87,10 +87,7 @@ def _pressure(field, data):
 
         if (ptype, "GFM_Metals_00") in self.field_list:
             self.nuclei_names = metal_elements
-            self.species_names = ["H"]
-            if (ptype, "NeutralHydrogenAbundance") in self.field_list:
-                self.species_names += ["H_p0", "H_p1"]
-            self.species_names += metal_elements
+            self.species_names = ["H"] + metal_elements
 
         if (ptype, "MagneticField") in self.field_list:
             setup_magnetic_field_aliases(self, ptype, "MagneticField")
@@ -130,8 +127,6 @@ def _h_p1_fraction(field, data):
                     field = f"{species}{suf}"
                     self.alias(("gas", field), (ptype, field))
 
-            self.alias(("gas", "H_nuclei_density"), ("gas", "H_number_density"))
-
         if (ptype, "ElectronAbundance") in self.field_list:
 
             # If we have ElectronAbundance but not NeutralHydrogenAbundance, assume the

yt/frontends/arepo/tests/test_outputs.py

@@ -3,7 +3,7 @@
 from collections import OrderedDict
 
 from yt.frontends.arepo.api import ArepoHDF5Dataset
-from yt.testing import ParticleSelectionComparison, requires_file
+from yt.testing import ParticleSelectionComparison, assert_allclose_units, requires_file
 from yt.utilities.answer_testing.framework import data_dir_load, requires_ds, sph_answer
 
 bullet_h5 = "ArepoBullet/snapshot_150.hdf5"
@@ -84,6 +84,15 @@ def test_index_override():
     assert len(open(tmpname).read()) == 0
 
 
+@requires_file(tng59_h5)
+def test_nh_density():
+    ds = data_dir_load(tng59_h5, kwargs={"bounding_box": _tng59_bbox})
+    ad = ds.all_data()
+    assert_allclose_units(
+        ad["gas", "H_number_density"], (ad["gas", "H_nuclei_density"])
+    )
+
+
 @requires_file(tng59_h5)
 def test_arepo_tng59_selection():
     ds = data_dir_load(tng59_h5, kwargs={"bounding_box": _tng59_bbox})