fix: xarray>=2025.03 compatibility

Author: yaugenst-flex

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - `fill` and `fill_structures` argument in `td.Simulation.plot_structures()` and `td.Simulation.plot()` respectively to disable fill and plot outlines of structures only.
+### Fixed
+- Compatibility with `xarray>=2025.03`.
 
 ## [2.8.1] - 2025-03-20
 

poetry.lock

@@ -24,7 +24,7 @@ documentation = "https://docs.flexcompute.com/projects/tidy3d/en/latest/"
 [tool.poetry.dependencies]
 python = ">=3.9,<3.14"
 pyroots = ">=0.5.0"
-xarray = ">=2023.08,<2025.03"
+xarray = ">=2023.08"
 importlib-metadata = ">=6.0.0"
 h5netcdf = "1.0.2"
 h5py = "^3.0.0"

pyproject.toml

@@ -0,0 +1,56 @@
+# test_compat.py
+
+import importlib
+import sys
+
+import pytest
+
+
+@pytest.fixture
+def restore_modules_and_meta_path():
+    """Fixture to restore sys.modules and sys.meta_path after test."""
+    original_modules = dict(sys.modules)
+    original_meta_path = list(sys.meta_path)
+    try:
+        yield
+    finally:
+        sys.modules.clear()
+        sys.modules.update(original_modules)
+        sys.meta_path[:] = original_meta_path
+
+
+def test_alignment_import(restore_modules_and_meta_path):
+    """Test normal import of alignment from xarray."""
+    # remove modules to ensure clean reload
+    for modname in ("tidy3d.compat", "xarray.structure.alignment", "xarray.core.alignment"):
+        if modname in sys.modules:
+            del sys.modules[modname]
+
+    import tidy3d.compat
+
+    assert tidy3d.compat.alignment is not None, "Failed to import alignment normally."
+
+
+def test_compat_import_fallback(restore_modules_and_meta_path):
+    """Test fallback to xarray.core.alignment when structure.alignment fails."""
+
+    # mock to simulate ImportError for xarray.structure.alignment
+    class MockImporter:
+        def find_spec(self, fullname, path=None, target=None):
+            if fullname == "xarray.structure.alignment":
+                raise ImportError
+            return None
+
+    sys.meta_path.insert(0, MockImporter())
+
+    # memove modules to force re-import
+    for modname in ("tidy3d.compat", "xarray.structure.alignment", "xarray.core.alignment"):
+        if modname in sys.modules:
+            del sys.modules[modname]
+
+    # import should trigger fallback mechanism
+    import tidy3d.compat
+
+    importlib.reload(tidy3d.compat)
+
+    assert tidy3d.compat.alignment is not None, "Expected fallback alignment to be imported."

tests/test_package/test_compat.py

@@ -0,0 +1,8 @@
+"""Compatibility layer for handling differences between package versions."""
+
+try:
+    from xarray.structure import alignment
+except ImportError:
+    from xarray.core import alignment
+
+__all__ = ["alignment"]

tidy3d/compat.py

@@ -10,13 +10,14 @@
 import numpy as np
 import xarray as xr
 from autograd.tracer import isbox
-from xarray.core import alignment, missing
+from xarray.core import missing
 from xarray.core.indexes import PandasIndex
 from xarray.core.indexing import _outer_to_numpy_indexer
 from xarray.core.types import InterpOptions, Self
 from xarray.core.utils import OrderedSet, either_dict_or_kwargs
 from xarray.core.variable import as_variable
 
+from ...compat import alignment
 from ...constants import (
     HERTZ,
     MICROMETER,