Merge pull request #36 from esm-tools/units

fixed the function signature for units handling.

src/pymorize/units.py

@@ -86,12 +86,7 @@ def handle_chemicals(
                 ureg.define(f"{match.group()} = {element.MW} * g")
 
 
-# FIXME: This needs to have a different signature!
-def handle_unit_conversion(
-    da: xr.DataArray,
-    rule_spec: Rule,
-    source_unit: Union[str, None] = None,
-) -> xr.DataArray:
+def handle_unit_conversion(da: xr.DataArray, rule: Rule) -> xr.DataArray:
     """Performs the unit-aware data conversion.
 
     If `source_unit` is provided, it is used instead of the unit from DataArray.
@@ -101,8 +96,6 @@ def handle_unit_conversion(
     da: ~xr.DataArray
     unit: str
         unit to convert data to
-    source_unit: str or None
-        Override the unit on ``da.attrs.unit`` if needed.
 
     Returns
     -------
@@ -112,14 +105,15 @@ def handle_unit_conversion(
     if not isinstance(da, xr.DataArray):
         raise TypeError(f"Expected xr.DataArray, got {type(da)}")
     # data_request_variable needs to be defined at this point
-    drv = rule_spec.data_request_variable
+    drv = rule.data_request_variable
     to_unit = drv.unit
+    model_unit = rule.get("model_unit")
     from_unit = da.attrs.get("units")
-    if source_unit is not None:
+    if model_unit is not None:
         logger.debug(
-            f"using user defined unit ({source_unit}) instead of ({from_unit}) from DataArray "
+            f"using user defined unit ({model_unit}) instead of ({from_unit}) from DataArray "
         )
-        from_unit = source_unit
+        from_unit = model_unit
     handle_chemicals(from_unit)
     handle_chemicals(to_unit)
     new_da = da.pint.quantify(from_unit)

tests/unit/test_units.py

@@ -99,11 +99,11 @@ def test_can_handle_chemical_elements(rule_with_units):
 def test_user_defined_units_takes_precedence_over_units_in_dataarray(rule_with_units):
     rule_spec = rule_with_units
     rule_spec.data_request_variable.unit = "g"
-    from_unit = "molC"
+    rule_spec.model_unit = "molC"
     to_unit = "g"
     da = xr.DataArray(10, attrs={"units": "kg"})
     # here, "molC" will be used instead of "kg"
-    new_da = handle_unit_conversion(da, rule_spec, from_unit)
+    new_da = handle_unit_conversion(da, rule_spec)
     assert new_da.data == np.array(periodic_table.Carbon.MW * 10)
     assert new_da.attrs["units"] == to_unit
 
@@ -121,10 +121,10 @@ def test_recognizes_previous_defined_chemical_elements():
 def test_works_when_both_units_are_None(rule_with_units):
     rule_spec = rule_with_units
     rule_spec.data_request_variable.unit = None
-    to_unit = None
+    rule_spec.model_unit = None
     da = xr.DataArray(10, attrs={"units": None})
-    new_da = handle_unit_conversion(da, rule_spec, to_unit)
-    assert new_da.attrs["units"] == to_unit
+    new_da = handle_unit_conversion(da, rule_spec)
+    assert new_da.attrs["units"] == None
 
 
 def test_works_when_both_units_are_empty_string(rule_with_units):
@@ -143,16 +143,16 @@ def test_when_target_units_is_None_overrides_existing_units(rule_with_units, fro
     drv = rule_spec.data_request_variable
     if hasattr(drv, "unit"):
         drv.unit = from_unit
-    to_unit = None
+    rule_spec.model_unit = None
     da = xr.DataArray(10, attrs={"units": from_unit})
-    new_da = handle_unit_conversion(da, rule_spec, to_unit)
-    assert new_da.attrs["units"] == to_unit
+    new_da = handle_unit_conversion(da, rule_spec)
+    assert new_da.attrs["units"] == drv.unit
 
 
 @pytest.mark.parametrize("from_unit", ["m/s", None])
 def test_when_tartget_unit_is_empty_string_raises_error(rule_with_units, from_unit):
     rule_spec = rule_with_units
-    to_unit = ""
+    rule_spec.model_unit = ""
     da = xr.DataArray(10, attrs={"units": from_unit})
     with pytest.raises(ValueError):
-        handle_unit_conversion(da, rule_spec, to_unit)
+        handle_unit_conversion(da, rule_spec)