Test interp nominal lon (#365)

CITATION.cff

@@ -12,7 +12,7 @@ authors:
   orcid: "https://orcid.org/0000-0002-1660-7822"
 - family-names: "Nicholas"
   given-names: "Thomas"
-  orcid: "0000-0002-2176-0530"
+  orcid: "https://orcid.org/0000-0002-2176-0530"
 - family-names: "Magin"
   given-names: "Justus"
   orcid: "https://orcid.org/0000-0002-4254-8002"
@@ -21,6 +21,10 @@ authors:
   given-names: "Markus"
   orcid: "https://orcid.org/0000-0001-7464-7075"
   affiliation: "Universität Hamburg, Germany"
+- family-names: "Angevaare"
+  given-names: "Joran J. R."
+  orcid: "https://orcid.org/0000-0003-3392-8123"
+  affiliation: "KNMI"
 
 title: "xMIP"
 url: "https://github.com/jbusecke/xMIP"

tests/test_preprocessing.py

@@ -20,6 +20,7 @@
     rename_cmip6,
     replace_x_y_nominal_lat_lon,
     sort_vertex_order,
+    _interp_nominal_lon,
 )
 
 
@@ -191,6 +192,44 @@ def test_replace_x_y_nominal_lat_lon(dask, nans):
     assert set(replaced_ds.lat.dims) == set(["x", "y"])
 
 
+def test_interp_nominal_lon():
+    """
+    Check that https://github.com/jbusecke/xMIP/issues/295 was fixed in https://github.com/jbusecke/xMIP/pull/296
+
+    In https://github.com/jbusecke/xMIP/blob/0270f4b4977d512adc2337d4a547b39e25d2f2da/tests/test_preprocessing.py,
+    the old issue was replicated (and illustrated that the tests would have failed then).
+    """
+
+    def _get_dummy_longitude() -> np.ndarray:
+        # Totally arbitrary data (although len(lon) has to be > 360 to see the issue)
+        lon = np.linspace(0, 360, 513)[:-1]
+
+        # Add some NaN values just as an example
+        lon[2 + 30 : len(lon) // 2 + 50] = np.nan
+        return lon
+
+    def _lons_parsed_make_sense(
+        input_lons: np.ndarray, lons_parsed: np.ndarray
+    ) -> bool:
+        """
+        Check if the parsed longitudes make sense.
+        Since we know that the input-lons are all monotonically increasing, the parsed lons should also do that.
+        """
+        accepted_differences_between_lon_coords = np.unique(np.diff(input_lons))
+        if len(accepted_differences_between_lon_coords) not in [1, 2]:
+            raise RuntimeError(
+                f"Cannot work with changed format of inputdata {accepted_differences_between_lon_coords}"
+            )
+        diff_pars_lons = np.unique(np.diff(lons_parsed))
+        return np.all(
+            [x in accepted_differences_between_lon_coords for x in diff_pars_lons]
+        )
+
+    lons = _get_dummy_longitude()
+    lons_parsed = _interp_nominal_lon(lons)
+    assert _lons_parsed_make_sense(lons, lons_parsed)
+
+
 @pytest.mark.parametrize(
     "coord",
     [

xmip/preprocessing.py

@@ -137,7 +137,7 @@ def broadcast_lonlat(ds, verbose=True):
     return ds
 
 
-def _interp_nominal_lon(lon_1d):
+def _interp_nominal_lon(lon_1d: np.ndarray) -> np.ndarray:
     x = np.arange(len(lon_1d))
     idx = np.isnan(lon_1d)
     # Assume that longitudes are cyclic (i.e. that the period equals the length of lon)