Make xESMF a required dependency

- Move xESMF to the "base" section in the conda env yml files
- Remove all code related to `_has_xesmf()` and move xESMF related imports outside of conditional statements
- Remove conditiondal statements related to xESMF that are no longer needed
- Remove mentions of xESMF being an optional dependency in the getting-started documentation page
- Update tests

conda-env/ci.yml

@@ -16,10 +16,8 @@ dependencies:
     - pandas
     - python-dateutil
     - xarray >=2022.02.0 # This version of Xarray drops support for Python 3.8.
-    - xgcm
-    # Optional - enables additional features.
-    # =========================================
     - xesmf >=0.7.0 # Constrained because https://github.com/pangeo-data/xESMF/issues/212.
+    - xgcm
     # Quality Assurance
     # ==================
     - types-python-dateutil

conda-env/dev.yml

@@ -16,10 +16,10 @@ dependencies:
     - pandas
     - python-dateutil
     - xarray >=2022.02.0 # This version of Xarray drops support for Python 3.8.
+    - xesmf >=0.7.0 # Constrained because https://github.com/pangeo-data/xESMF/issues/212.
     - xgcm
     # Optional - enables additional features.
     # =========================================
-    - xesmf >=0.7.0 # Constrained because https://github.com/pangeo-data/xESMF/issues/212.
     - matplotlib-base >=3.7.0
     - nc-time-axis=1.4.1
     # Documentation

docs/getting-started.rst

@@ -48,22 +48,14 @@ Installation
    The advantage with following this approach is that Mamba will attempt to resolve
    dependencies (e.g. ``python >= 3.8``) for compatibility.
 
-   To create an ``xcdat`` Mamba environment with ``xesmf`` (a recommended dependency),
+   To create an ``xcdat`` Mamba environment,
    run:
 
    .. code-block:: bash
 
-       >>> mamba create -n <ENV_NAME> -c conda-forge xcdat xesmf
+       >>> mamba create -n <ENV_NAME> -c conda-forge xcdat
        >>> mamba activate <ENV_NAME>
 
-   Note that ``xesmf`` is an optional dependency, which is required for using ``xesmf``
-   based horizontal regridding APIs in ``xcdat``. ``xesmf`` is not currently supported
-   on `Windows`_ because it depends on ``esmpy``, which also does not support Windows.
-   Windows users can try `WSL2`_ as a workaround.
-
-.. _Windows: https://github.com/conda-forge/esmf-feedstock/issues/64
-.. _WSL2: https://docs.microsoft.com/en-us/windows/wsl/install
-
 2. Install ``xcdat`` in an existing Mamba environment (`mamba install`_)
 
    You can also install ``xcdat`` in an existing Mamba environment, granted that Mamba
@@ -72,9 +64,7 @@ Installation
    .. code-block:: bash
 
        >>> mamba activate <ENV_NAME>
-       >>> mamba install -c conda-forge xcdat xesmf
-
-   Note: As above, ``xesmf`` is an optional dependency.
+       >>> mamba install -c conda-forge xcdat
 
 3. [Optional] Some packages that are commonly used with ``xcdat`` can be installed
    either in step 1 or step 2 above:

tests/__init__.py

@@ -1,7 +1,5 @@
 """Unit test package for xcdat."""
 from xarray.core.options import set_options
-from xarray.tests import _importorskip, requires_dask  # noqa: F401
+from xarray.tests import requires_dask  # noqa: F401
 
 set_options(warn_for_unclosed_files=False)
-
-has_xesmf, requires_xesmf = _importorskip("xesmf")

tests/test_regrid.py

@@ -9,11 +9,8 @@
 import pytest
 import xarray as xr
 
-from tests import fixtures, has_xesmf, requires_xesmf
-from xcdat.regridder import accessor, base, grid, regrid2, xgcm
-
-if has_xesmf:
-    from xcdat.regridder import xesmf
+from tests import fixtures
+from xcdat.regridder import accessor, base, grid, regrid2, xesmf, xgcm
 
 np.set_printoptions(threshold=sys.maxsize, suppress=True)
 
@@ -688,7 +685,6 @@ def test_reversed_extract_bounds(self):
         assert north[0], north[-1] == (60, 90)
 
 
-@requires_xesmf
 class TestXESMFRegridder:
     @pytest.fixture(autouse=True)
     def setup(self):
@@ -697,13 +693,6 @@ def setup(self):
         )
         self.new_grid = grid.create_uniform_grid(-90, 90, 4.0, -180, 180, 5.0)
 
-    @pytest.mark.xfail
-    def test_raises_error_if_xesmf_is_not_installed(self):
-        # TODO Find a way to mock the value of `_has_xesmf` to False or
-        # to remove the `xesmf` module entirely
-        with pytest.raises(ModuleNotFoundError):
-            xesmf.XESMFRegridder(self.ds, self.new_grid, "bilinear")
-
     def test_vertical_placeholder(self):
         ds = self.ds.copy()
 
@@ -1198,7 +1187,6 @@ def test_preserve_mask_from_input(self):
 
         xr.testing.assert_allclose(mask.ts, grid.mask)
 
-    @requires_xesmf
     def test_horizontal(self):
         output_grid = grid.create_gaussian_grid(32)
 
@@ -1348,7 +1336,6 @@ def test_vertical_tool_check(self, _get_input_grid):
         ):
             self.ac.vertical("ts", mock_data, tool="dummy", target_data=None)  # type: ignore
 
-    @requires_xesmf
     @pytest.mark.filterwarnings("ignore:.*invalid value.*divide.*:RuntimeWarning")
     def test_convenience_methods(self):
         ds = fixtures.generate_dataset(
@@ -1365,18 +1352,6 @@ def test_convenience_methods(self):
 
         assert output_regrid2.ts.shape == (15, 32, 65)
 
-    @pytest.mark.xfail
-    def test_raises_error_if_xesmf_is_not_installed(self):
-        # TODO Find a way to mock the value of `_has_xesmf` to False or
-        # to remove the `xesmf` module entirely
-        ds = fixtures.generate_dataset(
-            decode_times=True, cf_compliant=False, has_bounds=True
-        )
-
-        out_grid = grid.create_gaussian_grid(32)
-        with pytest.raises(ModuleNotFoundError):
-            ds.regridder.horizontal_xesmf("ts", out_grid, method="bilinear")
-
 
 class TestBase:
     def test_preserve_bounds(self):

xcdat/regridder/__init__.py

@@ -1,8 +1,5 @@
 from xcdat.regridder.accessor import RegridderAccessor
 from xcdat.regridder.regrid2 import Regrid2Regridder
+from xcdat.regridder.xesmf import XESMFRegridder
 from xcdat.regridder.xgcm import XGCMRegridder
 from xcdat.utils import _has_module
-
-_has_xesmf = _has_module("xesmf")
-if _has_xesmf:
-    from xcdat.regridder.xesmf import XESMFRegridder

xcdat/regridder/accessor.py

@@ -6,19 +6,14 @@
 import xarray as xr
 
 from xcdat.axis import CFAxisKey, get_dim_coords
-from xcdat.regridder import regrid2, xgcm
+from xcdat.regridder import regrid2, xesmf, xgcm
 from xcdat.regridder.grid import _validate_grid_has_single_axis_dim
-from xcdat.utils import _has_module
 
 HorizontalRegridTools = Literal["xesmf", "regrid2"]
-HORIZONTAL_REGRID_TOOLS = {"regrid2": regrid2.Regrid2Regridder}
-
-# TODO: Test this conditional.
-_has_xesmf = _has_module("xesmf")
-if _has_xesmf:  # pragma: no cover
-    from xcdat.regridder import xesmf
-
-    HORIZONTAL_REGRID_TOOLS["xesmf"] = xesmf.XESMFRegridder  # type: ignore
+HORIZONTAL_REGRID_TOOLS = {
+    "regrid2": regrid2.Regrid2Regridder,
+    "xesmf": xesmf.XESMFRegridder,
+}
 
 VerticalRegridTools = Literal["xgcm"]
 VERTICAL_REGRID_TOOLS = {"xgcm": xgcm.XGCMRegridder}
@@ -179,19 +174,9 @@ def horizontal_xesmf(
             stacklevel=2,
         )
 
-        # TODO: Test this conditional.
-        if _has_xesmf:  # pragma: no cover
-            regridder = HORIZONTAL_REGRID_TOOLS["xesmf"](
-                self._ds, output_grid, **options
-            )
+        regridder = HORIZONTAL_REGRID_TOOLS["xesmf"](self._ds, output_grid, **options)
 
-            return regridder.horizontal(data_var, self._ds)
-        else:  # pragma: no cover
-            raise ModuleNotFoundError(
-                "The `xesmf` package is required for horizontal regridding with "
-                "`xesmf`. Make sure your platform supports `xesmf` and it is installed "
-                "in your conda environment."
-            )
+        return regridder.horizontal(data_var, self._ds)
 
     # TODO Either provide generic `horizontal` and `vertical` methods or tool specific
     def horizontal_regrid2(
@@ -327,14 +312,6 @@ def horizontal(
 
         >>> output_data = ds.regridder.horizontal("ts", output_grid, tool="regrid2")
         """
-        # TODO: Test this conditional.
-        if tool == "xesmf" and not _has_xesmf:  # pragma: no cover
-            raise ModuleNotFoundError(
-                "The `xesmf` package is required for horizontal regridding with "
-                "`xesmf`. Make sure your platform supports `xesmf` and it is installed "
-                "in your conda environment."
-            )
-
         try:
             regrid_tool = HORIZONTAL_REGRID_TOOLS[tool]
         except KeyError as e:

xcdat/regridder/xesmf.py

@@ -1,21 +1,9 @@
 from typing import Any, Optional
 
 import xarray as xr
+import xesmf as xe
 
 from xcdat.regridder.base import BaseRegridder, _preserve_bounds
-from xcdat.utils import _has_module
-
-# TODO: Test this conditional.
-_has_xesmf = _has_module("xesmf")
-if _has_xesmf:  # pragma: no cover
-    import xesmf as xe
-else:  # pragma: no cover
-    raise ModuleNotFoundError(
-        "The `xesmf` package is required for horizontal regridding with `xesmf`. Make "
-        "sure your platform supports `xesmf` and it is installed in your conda "
-        "environment."
-    )
-
 
 VALID_METHODS = [
     "bilinear",