Remove in-house long time interval checking. (#279)

* Remove in-house long time interval checking.

* Restore is_long_time_interval() with a DeprecationWarning.

* Make test_deprecated a staticmethod.

* Fix to problem introduced in conflict resolution.

* Advance deprecation version.

Co-authored-by: Bill Little <bill.little@metoffice.gov.uk>

---------

Co-authored-by: Bill Little <bill.little@metoffice.gov.uk>

cf_units/__init__.py

@@ -16,6 +16,7 @@
 import copy
 import math
 from contextlib import contextmanager
+from warnings import warn
 
 import cftime
 import numpy as np
@@ -873,6 +874,12 @@ def is_long_time_interval(self):
         discrepancy means we cannot run self.num2date() on a time unit with
         a long time interval.
 
+        .. deprecated:: 3.3.0
+
+            Invalid long time intervals are now defended against within
+            cftime - do not use this routine, as cftime knows best what it can
+            and cannot support.
+
         Returns:
             Boolean.
 
@@ -887,6 +894,12 @@ def is_long_time_interval(self):
             True
 
         """
+        deprecation = (
+            "This method is no longer needed due to cftime's improved "
+            "handling of long time intervals."
+        )
+        warn(deprecation, DeprecationWarning, stacklevel=2)
+
         result = False
         long_time_intervals = ["year", "month"]
         if self.is_time_reference():
@@ -1830,15 +1843,6 @@ def cftime_unit(self):
         if self.calendar is None:
             raise ValueError("Unit has undefined calendar")
 
-        # `cftime` cannot parse long time intervals ("months" or "years").
-        if self.is_long_time_interval():
-            interval = self.origin.split(" ")[0]
-            emsg = (
-                'Time units with interval of "months", "years" '
-                '(or singular of these) cannot be processed, got "{!s}".'
-            )
-            raise ValueError(emsg.format(interval))
-
         #
         # ensure to strip out non-parsable 'UTC' postfix, which
         # is generated by UDUNITS-2 formatted output

cf_units/tests/integration/test_date2num.py

@@ -59,11 +59,3 @@ def test_convert_microsecond(self):
         res = date2num(date, self.unit, self.calendar)
 
         assert exp == pytest.approx(res)
-
-    def test_long_time_interval(self):
-        # This test should fail with an error that we need to catch properly.
-        unit = "years since 1970-01-01"
-        date = datetime.datetime(1970, 1, 1, 0, 0, 5)
-        exp_emsg = 'interval of "months", "years" .* got "years".'
-        with pytest.raises(ValueError, match=exp_emsg):
-            date2num(date, unit, self.calendar)

cf_units/tests/unit/unit/test_Unit.py

@@ -55,11 +55,6 @@ def test_no_change(self):
         # the same object.
         assert result is not u
 
-    def test_long_time_interval(self):
-        u = Unit("months since 1970-01-01", calendar="standard")
-        with pytest.raises(ValueError, match="cannot be processed"):
-            u.change_calendar("proleptic_gregorian")
-
     def test_wrong_calendar(self):
         u = Unit("days since 1900-01-01", calendar="360_day")
         with pytest.raises(
@@ -273,6 +268,14 @@ def test_type_conversion(self):
 
 
 class Test_is_long_time_interval:
+    @staticmethod
+    def test_deprecated():
+        unit = Unit("seconds since epoch")
+        with pytest.warns(
+            DeprecationWarning, match="This method is no longer needed"
+        ):
+            _ = unit.is_long_time_interval()
+
     def test_short_time_interval(self):
         # A short time interval is a time interval from seconds to days.
         unit = Unit("seconds since epoch")