Generic season index - no season is length 0

CHANGELOG.rst

@@ -16,6 +16,11 @@ Breaking changes
 ^^^^^^^^^^^^^^^^
 * As updated in ``cf_xarray>=0.9.3``, dimensionless quantities now use the "1" units attribute as specified by the CF conventions, previously an empty string was returned. (:pull:`1814`).
 
+Breaking changes
+^^^^^^^^^^^^^^^^
+* The definitions of the ``frost_free_season_start`` and ``frost_free_season_end`` have been slightly changed to be coherent with the ``frost_free_season_length`` and `xclim`'s notion of `season` in general. Indicator and indices signature have changed. (:pull:`1845`).
+* Season length indicators have been modified to return ``0`` for all cases where a proper season was not found, but the data is valid. Previously, a ``nan`` was given if neither a start or an end were found, even if the data was valid, and a ``0`` was given if an end was found but no start. (:pull:`1845`).
+
 Bug fixes
 ^^^^^^^^^
 * Fixed the indexer bug in the ``xclim.indices.standardized_index_fit_params`` when multiple or non-array indexers are specified and fitted parameters are reloaded from netCDF. (:issue:`1842`, :pull:`1843`).
@@ -26,6 +31,7 @@ Internal changes
 ^^^^^^^^^^^^^^^^
 * Changed the French translation of "wet days" from "jours mouillés" to "jours pluvieux". (:issue:`1825`, :pull:`1826`).
 * In order to adapt to changes in `pytest`, the doctest fixtures have been split from the main testing suite and doctests are now run using ``$ python -c 'from xclim.testing.utils import run_doctests; run_doctests()'``. (:pull:`1632`).
+* Added ``xclim.indices.generic.season`` to make season start, end, and length indices. Added a ``stat`` argument to ``xclim.indices.run_length.season`` to avoid returning a dataset. (:pull:`1845`).
 
 CI changes
 ^^^^^^^^^^

tests/test_indices.py

@@ -1160,7 +1160,7 @@ class TestGrowingSeasonLength:
         [
             ("1950-01-01", "1951-01-01", 0),  # No growing season
             ("2000-01-01", "2000-12-31", 365),  # All year growing season
-            ("2000-07-10", "2001-01-01", np.nan),  # End happens before start
+            ("2000-07-10", "2001-01-01", 0),  # End happens before start
             ("2000-06-15", "2001-01-01", 199),  # No end
             ("2000-06-15", "2000-07-15", 31),  # Normal case
         ],

tests/test_run_length.py

@@ -470,7 +470,7 @@ class TestRunsWithDates:
         [
             ("07-01", 210, 70),
             ("07-01", 190, 50),
-            ("04-01", 150, np.nan),  # date falls early
+            ("04-01", 150, 0),  # date falls early
             ("11-01", 150, 165),  # date ends late
             (None, 150, 10),  # no date, real length
         ],

tests/test_temperature.py

@@ -368,7 +368,7 @@ def test_real_data(self, atmosds):
 
 class TestFrostSeasonLength:
     def test_simple(self, tasmin_series):
-        a = np.zeros(730) + K2C + 15
+        a = np.zeros(731) + K2C + 15
         a[300:400] = K2C - 5
         a[404:407] = K2C - 5
         tasmin = tasmin_series(a, start="2000-01-01")
@@ -380,7 +380,7 @@ def test_simple(self, tasmin_series):
         np.testing.assert_array_equal(out, [np.nan, 100, np.nan])
 
         out = atmos.frost_season_length(tasmin=tasmin, mid_date="07-01", freq="YS")
-        np.testing.assert_array_equal(out, [np.nan, np.nan])
+        np.testing.assert_array_equal(out, [0, 181])
 
 
 class TestColdSpellDays: