Enable UGRID loading always; deprecate PARSE_UGRID_ON_LOAD. (#6054)

* Enable UGRID loading always; deprecate PARSE_UGRID_ON_LOAD.

* Fix tests that need unstructured points data, assuming test-data v2.25.

* Fix more tests for always-on ugrid loading.

---------

Co-authored-by: stephenworsley <49274989+stephenworsley@users.noreply.github.com>

.github/workflows/ci-tests.yml

@@ -50,7 +50,7 @@ jobs:
             session: "tests"
 
     env:
-      IRIS_TEST_DATA_VERSION: "2.22"
+      IRIS_TEST_DATA_VERSION: "2.25"
       ENV_NAME: "ci-tests"
 
     steps:

lib/iris/experimental/geovista.py

@@ -59,12 +59,10 @@ def cube_to_polydata(cube, **kwargs):
     .. testsetup::
 
         from iris import load_cube, sample_data_path
-        from iris.experimental.ugrid import PARSE_UGRID_ON_LOAD
 
         cube = load_cube(sample_data_path("air_temp.pp"))
         cube_w_time = load_cube(sample_data_path("A1B_north_america.nc"))
-        with PARSE_UGRID_ON_LOAD.context():
-            cube_mesh = load_cube(sample_data_path("mesh_C4_synthetic_float.nc"))
+        cube_mesh = load_cube(sample_data_path("mesh_C4_synthetic_float.nc"))
 
     >>> from iris.experimental.geovista import cube_to_polydata
 
@@ -212,11 +210,9 @@ def extract_unstructured_region(cube, polydata, region, **kwargs):
         from iris import load_cube, sample_data_path
         from iris.coords import AuxCoord
         from iris.cube import CubeList
-        from iris.experimental.ugrid import PARSE_UGRID_ON_LOAD
 
         file_path = sample_data_path("mesh_C4_synthetic_float.nc")
-        with PARSE_UGRID_ON_LOAD.context():
-            cube_w_mesh = load_cube(file_path)
+        cube_w_mesh = load_cube(file_path)
 
         level_cubes = CubeList()
         for height_level in range(72):

lib/iris/experimental/ugrid/__init__.py

@@ -5,6 +5,12 @@
 
 """Infra-structure for unstructured mesh support.
 
+.. deprecated:: 1.10
+
+    :data:`PARSE_UGRID_ON_LOAD` is due to be removed at next major release.
+    Please remove all uses of this, which are no longer needed :
+    UGRID loading is now **always** active for files containing a UGRID mesh.
+
 Based on CF UGRID Conventions (v1.0), https://ugrid-conventions.github.io/ugrid-conventions/.
 
 .. note::

lib/iris/experimental/ugrid/load.py

@@ -10,6 +10,11 @@
 
 Eventual destination: :mod:`iris.fileformats.netcdf`.
 
+.. seealso::
+
+    The UGRID Conventions,
+    https://ugrid-conventions.github.io/ugrid-conventions/
+
 """
 
 from contextlib import contextmanager
@@ -18,6 +23,7 @@
 import threading
 import warnings
 
+from ..._deprecation import warn_deprecated
 from ...config import get_logger
 from ...coords import AuxCoord
 from ...fileformats._nc_load_rules.helpers import get_attr_units, get_names
@@ -60,20 +66,20 @@ def __init__(self):
         :const:`~iris.experimental.ugrid.load.PARSE_UGRID_ON_LOAD`.
         Use :meth:`context` to temporarily activate.
 
-        .. seealso::
-
-            The UGRID Conventions,
-            https://ugrid-conventions.github.io/ugrid-conventions/
+        Notes
+        -----
+            .. deprecated:: 1.10
+        Do not use -- due to be removed at next major release :
+        UGRID loading is now **always** active for files containing a UGRID mesh.
 
         """
-        self._state = False
 
     def __bool__(self):
-        return self._state
+        return True
 
     @contextmanager
     def context(self):
-        """Temporarily activate experimental UGRID-aware NetCDF loading.
+        """Activate UGRID-aware NetCDF loading.
 
         Use the standard Iris loading API while within the context manager. If
         the loaded file(s) include any UGRID content, this will be parsed and
@@ -89,12 +95,35 @@ def context(self):
                                          constraint=my_constraint,
                                          callback=my_callback)
 
+        Notes
+        -----
+            .. deprecated:: 1.10
+        Do not use -- due to be removed at next major release :
+        UGRID loading is now **always** active for files containing a UGRID mesh.
+
+        Examples
+        --------
+        Replace usage, for example:
+
+        .. code-block:: python
+
+            with iris.experimental.ugrid.PARSE_UGRID_ON_LOAD.context():
+                mesh_cubes = iris.load(path)
+
+        with:
+
+        .. code-block:: python
+
+            mesh_cubes = iris.load(path)
+
         """
-        try:
-            self._state = True
-            yield
-        finally:
-            self._state = False
+        wmsg = (
+            "iris.experimental.ugrid.load.PARSE_UGRID_ON_LOAD has been deprecated "
+            "and will be removed. Please remove all uses : these are no longer needed, "
+            "as UGRID loading is now applied to any file containing a mesh."
+        )
+        warn_deprecated(wmsg)
+        yield
 
 
 #: Run-time switch for experimental UGRID-aware NetCDF loading. See :class:`~iris.experimental.ugrid.load.ParseUGridOnLoad`.
@@ -174,15 +203,6 @@ def load_meshes(uris, var_name=None):
 
     from ...fileformats import FORMAT_AGENT
 
-    if not PARSE_UGRID_ON_LOAD:
-        # Explicit behaviour, consistent with netcdf.load_cubes(), rather than
-        #  an invisible assumption.
-        message = (
-            f"PARSE_UGRID_ON_LOAD is {bool(PARSE_UGRID_ON_LOAD)}. Must be "
-            f"True to enable mesh loading."
-        )
-        raise ValueError(message)
-
     if isinstance(uris, str):
         uris = [uris]
 

lib/iris/experimental/ugrid/mesh.py

@@ -786,14 +786,12 @@ def from_coords(cls, *coords):
 
             from iris import load_cube, sample_data_path
             from iris.experimental.ugrid import (
-                PARSE_UGRID_ON_LOAD,
                 MeshXY,
                 MeshCoord,
             )
 
             file_path = sample_data_path("mesh_C4_synthetic_float.nc")
-            with PARSE_UGRID_ON_LOAD.context():
-                cube_w_mesh = load_cube(file_path)
+            cube_w_mesh = load_cube(file_path)
 
         Examples
         --------

lib/iris/fileformats/netcdf/loader.py

@@ -583,7 +583,6 @@ def load_cubes(file_sources, callback=None, constraints=None):
     # Deferred import to avoid circular imports.
     from iris.experimental.ugrid.cf import CFUGridReader
     from iris.experimental.ugrid.load import (
-        PARSE_UGRID_ON_LOAD,
         _build_mesh_coords,
         _meshes_from_cf,
     )
@@ -600,15 +599,8 @@ def load_cubes(file_sources, callback=None, constraints=None):
 
     for file_source in file_sources:
         # Ingest the file.  At present may be a filepath or an open netCDF4.Dataset.
-        meshes = {}
-        if PARSE_UGRID_ON_LOAD:
-            cf_reader_class = CFUGridReader
-        else:
-            cf_reader_class = iris.fileformats.cf.CFReader
-
-        with cf_reader_class(file_source) as cf:
-            if PARSE_UGRID_ON_LOAD:
-                meshes = _meshes_from_cf(cf)
+        with CFUGridReader(file_source) as cf:
+            meshes = _meshes_from_cf(cf)
 
             # Process each CF data variable.
             data_variables = list(cf.cf_group.data_variables.values()) + list(
@@ -626,8 +618,7 @@ def load_cubes(file_sources, callback=None, constraints=None):
                 mesh_name = None
                 mesh = None
                 mesh_coords, mesh_dim = [], None
-                if PARSE_UGRID_ON_LOAD:
-                    mesh_name = getattr(cf_var, "mesh", None)
+                mesh_name = getattr(cf_var, "mesh", None)
                 if mesh_name is not None:
                     try:
                         mesh = meshes[mesh_name]

lib/iris/tests/integration/experimental/geovista/test_cube_to_poly.py

@@ -8,7 +8,6 @@
 
 from iris import load_cube
 from iris.experimental.geovista import cube_to_polydata
-from iris.experimental.ugrid import PARSE_UGRID_ON_LOAD
 from iris.tests import get_data_path
 
 
@@ -57,8 +56,7 @@ def test_integration_mesh():
         ]
     )
 
-    with PARSE_UGRID_ON_LOAD.context():
-        cube = load_cube(file_path, "conv_rain")
+    cube = load_cube(file_path, "conv_rain")
 
     polydata = cube_to_polydata(cube[0, :])
     # This is a known good output, we have plotted the result and checked it.

lib/iris/tests/integration/experimental/geovista/test_extract_unstructured_region.py

@@ -8,7 +8,6 @@
 
 from iris import load_cube
 from iris.experimental.geovista import cube_to_polydata, extract_unstructured_region
-from iris.experimental.ugrid import PARSE_UGRID_ON_LOAD
 from iris.tests import get_data_path
 
 
@@ -21,8 +20,7 @@ def test_face_region_extraction():
         ]
     )
 
-    with PARSE_UGRID_ON_LOAD.context():
-        global_cube = load_cube(file_path, "conv_rain")
+    global_cube = load_cube(file_path, "conv_rain")
     polydata = cube_to_polydata(global_cube[0, :])
     region = BBox(lons=[0, 70, 70, 0], lats=[-25, -25, 45, 45])
 

lib/iris/tests/integration/experimental/test_regrid_ProjectedUnstructured.py

@@ -28,7 +28,7 @@
 class TestProjectedUnstructured(tests.IrisTest):
     def setUp(self):
         path = tests.get_data_path(
-            ("NetCDF", "unstructured_grid", "theta_nodal_xios.nc")
+            ("NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc")
         )
         self.src = iris.load_cube(path, "Potential Temperature")
 

lib/iris/tests/integration/experimental/test_ugrid_load.py

@@ -18,7 +18,7 @@
 import pytest
 
 from iris import Constraint, load
-from iris.experimental.ugrid.load import PARSE_UGRID_ON_LOAD, load_mesh, load_meshes
+from iris.experimental.ugrid.load import load_mesh, load_meshes
 from iris.experimental.ugrid.mesh import MeshXY
 from iris.tests.stock.netcdf import (
     _file_from_cdl_template as create_file_from_cdl_template,
@@ -47,8 +47,7 @@ def ugrid_load(uris, constraints=None, callback=None):
             constraints = [constraints]
         constraints.append(filter_orphan_connectivities)
 
-    with PARSE_UGRID_ON_LOAD.context():
-        return load(uris, constraints, callback)
+    return load(uris, constraints, callback)
 
 
 @tests.skip_data
@@ -110,12 +109,11 @@ def test_3D_veg_pseudo_levels(self):
         )
 
     def test_no_mesh(self):
-        with PARSE_UGRID_ON_LOAD.context():
-            cube_list = load(
-                tests.get_data_path(
-                    ["NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc"]
-                )
+        cube_list = load(
+            tests.get_data_path(
+                ["NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc"]
             )
+        )
         self.assertTrue(all([cube.mesh is None for cube in cube_list]))
 
 
@@ -207,10 +205,9 @@ def test_mesh_no_cf_role(self):
 @tests.skip_data
 class Test_load_mesh(tests.IrisTest):
     def common_test(self, file_name, mesh_var_name):
-        with PARSE_UGRID_ON_LOAD.context():
-            mesh = load_mesh(
-                tests.get_data_path(["NetCDF", "unstructured_grid", file_name])
-            )
+        mesh = load_mesh(
+            tests.get_data_path(["NetCDF", "unstructured_grid", file_name])
+        )
         # NOTE: cannot use CML tests as this isn't supported for non-Cubes.
         self.assertIsInstance(mesh, MeshXY)
         self.assertEqual(mesh.var_name, mesh_var_name)
@@ -225,12 +222,11 @@ def test_mesh_file(self):
         self.common_test("mesh_C12.nc", "dynamics")
 
     def test_no_mesh(self):
-        with PARSE_UGRID_ON_LOAD.context():
-            meshes = load_meshes(
-                tests.get_data_path(
-                    ["NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc"]
-                )
+        meshes = load_meshes(
+            tests.get_data_path(
+                ["NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc"]
             )
+        )
         self.assertDictEqual({}, meshes)
 
 

lib/iris/tests/integration/experimental/test_ugrid_save.py

@@ -14,7 +14,6 @@
 import tempfile
 
 import iris
-from iris.experimental.ugrid.load import PARSE_UGRID_ON_LOAD
 import iris.fileformats.netcdf
 from iris.tests.stock.netcdf import _add_standard_data, ncgen_from_cdl
 
@@ -48,8 +47,7 @@ def test_example_result_cdls(self):
             # Fill in blank data-variables.
             _add_standard_data(target_ncfile_path)
             # Load as Iris data
-            with PARSE_UGRID_ON_LOAD.context():
-                cubes = iris.load(target_ncfile_path)
+            cubes = iris.load(target_ncfile_path)
             # Re-save, to check the save behaviour.
             resave_ncfile_path = str(self.temp_dir / f"{ex_name}_resaved.nc")
             iris.save(cubes, resave_ncfile_path)
@@ -69,8 +67,7 @@ def test_example_roundtrips(self):
             # Fill in blank data-variables.
             _add_standard_data(target_ncfile_path)
             # Load the original as Iris data
-            with PARSE_UGRID_ON_LOAD.context():
-                orig_cubes = iris.load(target_ncfile_path)
+            orig_cubes = iris.load(target_ncfile_path)
 
             if "ex4" in ex_name:
                 # Discard the extra formula terms component cubes
@@ -80,8 +77,7 @@ def test_example_roundtrips(self):
             # Save-and-load-back to compare the Iris saved result.
             resave_ncfile_path = str(self.temp_dir / f"{ex_name}_resaved.nc")
             iris.save(orig_cubes, resave_ncfile_path)
-            with PARSE_UGRID_ON_LOAD.context():
-                savedloaded_cubes = iris.load(resave_ncfile_path)
+            savedloaded_cubes = iris.load(resave_ncfile_path)
 
             # This should match the original exactly
             # ..EXCEPT for our inability to compare meshes.

lib/iris/tests/integration/test_regridding.py

@@ -98,7 +98,7 @@ def test_nearest(self):
 class TestUnstructured(tests.IrisTest):
     def setUp(self):
         path = tests.get_data_path(
-            ("NetCDF", "unstructured_grid", "theta_nodal_xios.nc")
+            ("NetCDF", "unstructured_grid", "theta_nodal_not_ugrid.nc")
         )
         self.src = iris.load_cube(path, "Potential Temperature")
         self.grid = simple_3d()[0, :, :]