feat(io): stamp linopy version into netCDF export

doc/release_notes.rst

@@ -4,6 +4,8 @@ Release Notes
 Upcoming Version
 ----------------
 
+* ``Model.to_netcdf`` now records the writing linopy version in the ``_linopy_version`` dataset attribute. Files written by older versions (without the attribute) continue to read unchanged.
+
 Version 0.8.0
 -------------
 

linopy/io.py

@@ -12,6 +12,7 @@
 import time
 import warnings
 from collections.abc import Callable, Iterable
+from importlib.metadata import version
 from io import BufferedWriter
 from pathlib import Path
 from tempfile import TemporaryDirectory
@@ -37,6 +38,8 @@
 
 logger = logging.getLogger(__name__)
 
+NETCDF_VERSION_ATTR = "_linopy_version"
+
 
 ufunc_kwargs = dict(vectorize=True)
 concat_kwargs = dict(dim=CONCAT_DIM, coords="minimal")
@@ -971,6 +974,7 @@ def with_prefix(ds: xr.Dataset, prefix: str) -> xr.Dataset:
     scalars = {k: getattr(m, k) for k in m.scalar_attrs}
     ds = xr.merge(vars + cons + obj + params, combine_attrs="drop_conflicts")
     ds = ds.assign_attrs(scalars)
+    ds.attrs[NETCDF_VERSION_ATTR] = version("linopy")
     if m._relaxed_registry:
         ds.attrs["_relaxed_registry"] = json.dumps(m._relaxed_registry)
     if m._piecewise_formulations:

test/test_io.py

@@ -221,6 +221,20 @@ def test_read_netcdf_with_multiindex_legacy_list_attr(
     assert_model_equal(m, read_netcdf(fn_legacy))
 
 
+def test_read_netcdf_without_version_stamp(model: Model, tmp_path: Path) -> None:
+    from linopy.io import NETCDF_VERSION_ATTR
+
+    fn = tmp_path / "test.nc"
+    model.to_netcdf(fn)
+
+    ds = xr.load_dataset(fn).load()
+    del ds.attrs[NETCDF_VERSION_ATTR]
+    fn_legacy = tmp_path / "legacy.nc"
+    ds.to_netcdf(fn_legacy)
+
+    assert_model_equal(model, read_netcdf(fn_legacy))
+
+
 @pytest.mark.skipif("gurobi" not in available_solvers, reason="Gurobipy not installed")
 def test_to_file_lp(model: Model, tmp_path: Path) -> None:
     import gurobipy