Test conversions (#372)

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### Pull Request Checklist:
- [x] This PR addresses an already opened issue (for bug fixes /
features)
    - This PR fixes #xyz
- [x] (If applicable) Documentation has been added / updated (for bug
fixes / features).
- [x] (If applicable) Tests have been added.
- [x] This PR does not seem to break the templates.
- [x] CHANGES.rst has been updated (with summary of main changes).
- [x] Link to issue (:issue:`number`) and pull request (:pull:`number`)
has been added.

### What kind of change does this PR introduce?

* Tests for `xclim_modules/conversions.py`
* Added `context="hydro"` to the precipitation conversion.
* Fixed a bug in `tasmin/max_from_dtr` when `dtr` was in different units
than `tasmin/max`.

### Does this PR introduce a breaking change?

* I changed `dtr` (the function) to `dtr_from_minmax` to avoid conflicts
with `dtr` (the variable). This is only breaking if people directly used
the Python file, which should be no one.


### Other information:

CHANGES.rst

@@ -10,14 +10,15 @@ Breaking changes
 ^^^^^^^^^^^^^^^^
 * Removed support for the old instances of the `region` argument in ``spatial_mean``, ``extract_dataset``, and ``subset``. (:pull:`367`).
 * Removed ``xscen.extract.clisops_subset``. (:pull:`367`).
+* ``dtr`` (the function) was renamed to ``dtr_from_minmax`` to avoid confusion with the `dtr` variable. (:pull:`372`).
 
 Internal changes
 ^^^^^^^^^^^^^^^^
 * Updated the `cookiecutter` template to the latest version. (:pull:`358`):
     * Addresses a handful of misconfigurations in the GitHub Workflows.
     * Added a few free `grep`-based hooks for finding unwanted artifacts in the code base.
     * Updated `ruff` to v0.2.0 and `black` to v24.2.0.
-* Added more tests. (:pull:`366`, :pull:`367`).
+* Added more tests. (:pull:`366`, :pull:`367`, :pull:`372`).
 * Refactored ``xs.spatial.subset`` into smaller functions. (:pull:`367`).
 * An `encoding` argument was added to ``xs.config.load_config``. (:pull:`370`).
 
@@ -29,6 +30,7 @@ Bug fixes
 * Fixed bug for adding the preprocessing attributes inside the `adjust` function. (:pull:`366`).
 * Fixed a bug to accept `group = False` in `adjust` function. (:pull:`366`).
 * `creep_weights` now correctly handles the case where the grid is small, `n` is large, and `mode=wrap`. (:issue:`367`).
+* Fixed a bug in ``tasmin_from_dtr`` and ``tasmax_from_dtr``, when `dtr` units differed from tasmin/max. (:pull:`372`).
 
 v0.8.3 (2024-02-28)
 -------------------

tests/test_xclimmod_conversions.py

@@ -0,0 +1,61 @@
+import numpy as np
+from xclim.testing.helpers import test_timeseries as timeseries
+
+import xscen.xclim_modules.conversions as conv
+
+
+def test_precipitation():
+    prsn = timeseries(np.ones(3), variable="prsn", start="2001-01-01", freq="D")
+    prlp = timeseries(
+        np.ones(3) * 10, variable="pr", start="2001-01-01", freq="D", units="mm d-1"
+    )
+    prlp.attrs["standard_name"] = "liquid_precipitation_flux"
+
+    pr = conv.precipitation(prsn, prlp)
+    assert pr.attrs["units"] == prsn.attrs["units"]
+    np.testing.assert_array_equal(pr, prsn + prlp / 86400)
+
+
+def test_tasmin_from_dtr():
+    dtr = timeseries(
+        np.ones(3) * 10, variable="tas", start="2001-01-01", freq="D", units="C"
+    )
+    dtr.attrs["standard_name"] = "daily_temperature_range"
+    tasmax = timeseries(
+        np.ones(3) * 20, variable="tasmax", start="2001-01-01", freq="D"
+    )
+
+    tasmin = conv.tasmin_from_dtr(dtr, tasmax)
+    assert tasmin.attrs["units"] == tasmax.attrs["units"]
+    np.testing.assert_array_equal(
+        tasmin, tasmax - dtr
+    )  # DTR in Celsius should not matter in the result, for a tasmax in Kelvin
+
+
+def test_tasmax_from_dtr():
+    dtr = timeseries(
+        np.ones(3) * 10, variable="tas", start="2001-01-01", freq="D", units="C"
+    )
+    dtr.attrs["standard_name"] = "daily_temperature_range"
+    tasmin = timeseries(
+        np.ones(3) * 10, variable="tasmin", start="2001-01-01", freq="D"
+    )
+
+    tasmax = conv.tasmax_from_dtr(dtr, tasmin)
+    assert tasmax.attrs["units"] == tasmin.attrs["units"]
+    np.testing.assert_array_equal(
+        tasmax, tasmin + dtr
+    )  # DTR in Celsius should not matter in the result, for a tasmin in Kelvin
+
+
+def test_dtr():
+    tasmax = timeseries(
+        np.ones(3) * 20, variable="tasmax", start="2001-01-01", freq="D", units="C"
+    )
+    tasmin = timeseries(
+        np.ones(3) * 10, variable="tasmin", start="2001-01-01", freq="D"
+    )
+
+    dtr = conv.dtr_from_minmax(tasmin, tasmax)
+    assert dtr.attrs["units"] == "K"
+    np.testing.assert_array_equal(dtr, (tasmax + 273.15) - tasmin)

xscen/xclim_modules/conversions.py

@@ -24,7 +24,7 @@ def precipitation(prsn: xr.DataArray, prlp: xr.DataArray) -> xr.DataArray:
     xr.DataArray, [same as prsn]
       Surface precipitation flux (all phases)
     """
-    prlp = convert_units_to(prlp, prsn)
+    prlp = convert_units_to(prlp, prsn, context="hydro")
     pr = prsn + prlp
     pr.attrs["units"] = prsn.attrs["units"]
     return pr
@@ -48,9 +48,12 @@ def tasmin_from_dtr(dtr: xr.DataArray, tasmax: xr.DataArray) -> xr.DataArray:
     xr.DataArray, [same as tasmax]
       Daily minimum temperature
     """
-    dtr = convert_units_to(dtr, tasmax)
+    out_units = tasmax.units
+    # To prevent strange behaviors that could arise from changing DTR units, we change the units of tasmax to match DTR
+    tasmax = convert_units_to(tasmax, dtr)
     tasmin = tasmax - dtr
-    tasmin.attrs["units"] = tasmax.units
+    tasmin.attrs["units"] = dtr.units
+    tasmin = convert_units_to(tasmin, out_units)
     return tasmin
 
 
@@ -72,14 +75,17 @@ def tasmax_from_dtr(dtr: xr.DataArray, tasmin: xr.DataArray) -> xr.DataArray:
     xr.DataArray, [same as tasmin]
       Daily maximum temperature
     """
-    dtr = convert_units_to(dtr, tasmin)
+    out_units = tasmin.attrs["units"]
+    # To prevent strange behaviors that could arise from changing DTR units, we change the units of tasmin to match DTR
+    tasmin = convert_units_to(tasmin, dtr)
     tasmax = tasmin + dtr
-    tasmax.attrs["units"] = tasmin.units
+    tasmax.attrs["units"] = dtr.attrs["units"]
+    tasmax = convert_units_to(tasmax, out_units)
     return tasmax
 
 
 @declare_units(tasmin="[temperature]", tasmax="[temperature]")
-def dtr(tasmin: xr.DataArray, tasmax: xr.DataArray) -> xr.DataArray:
+def dtr_from_minmax(tasmin: xr.DataArray, tasmax: xr.DataArray) -> xr.DataArray:
     """DTR computed from tasmin and tasmax.
 
     Dtr as tasmin subtracted from tasmax.

xscen/xclim_modules/conversions.yml

@@ -65,7 +65,7 @@ indicators:
       - var_name: evspsblpot
   dtr:
     src_freq: D
-    compute: dtr
+    compute: dtr_from_minmax
     cf_attrs:
       units: K
       description: Daily temperature range.