Deprecate usage of ndsl.Namelist

ndsl/namelist.py

@@ -1,4 +1,5 @@
 import dataclasses
+import warnings
 from typing import Any, Self
 
 import f90nml
@@ -617,6 +618,15 @@ def from_f90nml(cls, namelist: f90nml.Namelist) -> Self:
         }
         return cls(**namelist_dict)
 
+    def __post_init__(self) -> None:
+        warnings.warn(
+            "Usage of `ndsl.Namelist` is discouraged. The class will be "
+            "removed in the next version together with `NamelistDefaults`, see "
+            "https://github.com/NOAA-GFDL/NDSL/issues/64.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+
 
 def namelist_to_flatish_dict(nml_input: Any) -> dict:
     nml = dict(nml_input)

tests/test_namelist.py

@@ -0,0 +1,8 @@
+import pytest
+
+from ndsl import Namelist
+
+
+def test_ndsl_namelist_deprecation() -> None:
+    with pytest.deprecated_call():
+        my_namelist = Namelist()