Pyudunits2

.github/workflows/default-tests.yml

@@ -11,6 +11,11 @@ jobs:
       matrix:
         python-version: [ "3.10", "3.11", "3.12", "3.13" ]
         os: [ windows-latest, ubuntu-latest, macos-latest ]
+        cf_units: [ false ]
+        include:
+          - python-version: "3.10"
+            os: "ubuntu-latest"
+            cf_units: true
       fail-fast: false
     defaults:
       run:
@@ -30,6 +35,11 @@ jobs:
           --file test_requirements.txt
           --channel conda-forge
 
+    - name: Test with cf-units (optional)
+      if: matrix.cf_units == true
+      run: >-
+        micromamba install cf-units --channel conda-forge
+
     - name: Install compliance-checker
       run: |
         python -m pip install -e . --no-deps --force-reinstall

compliance_checker/cf/cf_1_6.py

@@ -5,7 +5,6 @@
 import cftime
 import numpy as np
 import regex
-from cf_units import Unit
 
 from compliance_checker import cfutil
 from compliance_checker.base import BaseCheck, Result, TestCtx
@@ -18,6 +17,7 @@
     grid_mapping_dict16,
 )
 from compliance_checker.cf.cf_base import CFNCCheck, appendix_a_base
+from compliance_checker.cfunits import Unit
 
 logger = logging.getLogger(__name__)
 
@@ -2848,7 +2848,9 @@ def _cell_measures_core(self, ds, var, external_set, variable_template):
                         valid = False
                         reasoning.append(conversion_failure_msg)
                     else:
-                        if not cell_measure_units.is_convertible(Unit(f"m{exponent}")):
+                        if not cell_measure_units.is_convertible(
+                            Unit(f"m{exponent}"),
+                        ):
                             valid = False
                             reasoning.append(conversion_failure_msg)
                     if not set(cell_measure_var.dimensions).issubset(var.dimensions):

compliance_checker/cf/util.py

@@ -8,10 +8,10 @@
 from typing import Union
 
 import requests
-from cf_units import Unit
 from lxml import etree
 from netCDF4 import Dataset, Dimension, Group, Variable
 
+from compliance_checker.cfunits import Unit
 from compliance_checker.cfutil import units_convertible
 
 # copied from paegan

compliance_checker/cfunits.py

@@ -0,0 +1,76 @@
+import pyudunits2
+
+try:
+    import cf_units
+except ImportError:
+    cf_units = False
+
+UT_SYSTEM = None
+
+
+class PyUdunits2:
+    """Workaround for the differences in pyudunits2 and cf-units.
+
+    NB: Some of these may change and/or get implemented upstream. Pyudunits2 is new and in-flux.
+
+    1/4 Raise the same ValueError to match cf-unit errors.
+    2/4 Creates an empty unit from None to mimic cf-unit's Unit('unknown')
+    3/4 Add a definition object that is ust units.expanded()
+    """
+
+    def __init__(self, units: str | None):
+        """Keep unit system so we can convert from string later."""
+        global UT_SYSTEM
+        if UT_SYSTEM is None:
+            UT_SYSTEM = pyudunits2.UnitSystem.from_udunits2_xml()
+
+        self.ut_system = UT_SYSTEM
+
+        if units is None:
+            units = ""
+
+        try:
+            self.units = self.ut_system.unit(units)
+        except (SyntaxError, pyudunits2.UnresolvableUnitException) as err:
+            raise ValueError from err
+        self.definition = self.units.expanded()
+
+    def __eq__(self, other):
+        return self.units == other
+
+    def is_dimensionless(self):
+        return self.units.is_dimensionless()
+
+    def is_time_reference(self):
+        return isinstance(self.units, pyudunits2.DateUnit)
+
+    def is_convertible(self, other):
+        if isinstance(other, str):
+            other = self.ut_system.unit(other)
+        elif isinstance(other, (PyUdunits2)):
+            other = other.units
+        else:
+            msg = f"Expected valid unit string or pyudunits2 unit object. Got {other}."
+            raise ValueError(msg)
+
+        # FIXME: cf-units Workaround 1/4 -> cf_units.Unit(None) -> Unit('unknown').
+        if "" in (self.units.expanded(), other.expanded()):
+            return False
+
+        convertible = self.units.is_convertible_to(other)
+        # FIXME: cf-units Workaround 2/4 -> time is not convertible to time reference.
+
+        # Both are time reference confirm.
+        if self.is_time_reference() and isinstance(other, pyudunits2.DateUnit):
+            convertible = True
+
+        return convertible
+
+
+if cf_units:
+    PyUdunits2 = cf_units.Unit
+
+
+class Unit(PyUdunits2):
+    def __init__(self, units):
+        super().__init__(units)

compliance_checker/cfutil.py

@@ -9,7 +9,7 @@
 from functools import lru_cache, partial
 from importlib.resources import files
 
-from cf_units import Unit
+from compliance_checker.cfunits import Unit
 
 _UNITLESS_DB = None
 _SEA_NAMES = None
@@ -111,7 +111,9 @@ def is_dimensionless_standard_name(standard_name_table, standard_name):
         f".//entry[@id='{standard_name}']",
     )
     if found_standard_name is not None:
-        canonical_units = Unit(found_standard_name.find("canonical_units").text)
+        canonical_units = Unit(
+            found_standard_name.find("canonical_units").text,
+        )
         return canonical_units.is_dimensionless()
     # if the standard name is not found, assume we need units for the time being
     else:
@@ -2039,6 +2041,6 @@ def units_convertible(units1, units2):
     try:
         u1 = Unit(units1)
         u2 = Unit(units2)
-    except ValueError:
+    except (ValueError, NotImplementedError):
         return False
     return u1.is_convertible(u2)

compliance_checker/ioos.py

@@ -6,7 +6,6 @@
 from numbers import Number
 
 import validators
-from cf_units import Unit
 from lxml.etree import XPath
 from owslib.namespaces import Namespaces
 
@@ -23,6 +22,7 @@
 )
 from compliance_checker.cf import util as cf_util  # not to be confused with cfutil.py
 from compliance_checker.cf.cf import CF1_6Check, CF1_7Check
+from compliance_checker.cfunits import Unit
 from compliance_checker.cfutil import (
     get_geophysical_variables,
     get_instrument_variables,
@@ -1377,7 +1377,6 @@ def check_vertical_coordinates(self, ds):
                 "mile",
                 "fathom",
             )
-
             unit_def_set = {
                 Unit(unit_str).definition for unit_str in expected_unit_strs
             }

pyproject.toml

@@ -9,7 +9,7 @@ requires = [
 [project]
 name = "compliance-checker"
 description = "Checks Datasets and SOS endpoints for standards compliance"
-readme = "README.md"
+readme = { file = "README.md", content-type = "text/markdown" }
 license = { text = "Apache-2.0" }
 maintainers = [
   { name = "Dave Foster", email = "[email protected]" },
@@ -38,6 +38,7 @@ dynamic = [
   "dependencies",
   "version",
 ]
+optional-dependencies.extras = [ "cf-units>=2" ]
 urls.documentation = "https://ioos.github.io/compliance-checker"
 urls.homepage = "https://compliance.ioos.us/index.html"
 urls.repository = "https://github.com/ioos/compliance-checker"
@@ -79,7 +80,6 @@ compliance_checker = [
 dependencies = { file = [
   "requirements.txt",
 ] }
-readme = { file = "README.md", content-type = "text/markdown" }
 
 [tool.setuptools_scm]
 write_to = "compliance_checker/_version.py"

requirements.txt

@@ -1,4 +1,3 @@
-cf-units>=2
 cftime>=1.1.0
 isodate>=0.6.1
 jinja2>=2.7.3
@@ -9,6 +8,7 @@ packaging
 pendulum>=1.2.4
 pygeoif>=0.6
 pyproj>=2.2.1
+pyudunits2
 regex>=2017.07.28
 requests>=2.2.1
 setuptools>=15.0