Masking and overflow checks for datetimeindex and timedeltaindex ops

pandas/core/indexes/datetimes.py

@@ -29,6 +29,7 @@
 import pandas.core.dtypes.concat as _concat
 from pandas.errors import PerformanceWarning
 from pandas.core.common import _values_from_object, _maybe_box
+from pandas.core.algorithms import checked_add_with_arr
 
 from pandas.core.indexes.base import Index, _index_shared_docs
 from pandas.core.indexes.numeric import Int64Index, Float64Index
@@ -777,7 +778,8 @@ def _sub_datelike(self, other):
                                 "timezones or no timezones")
             else:
                 i8 = self.asi8
-                result = i8 - other.value
+                result = checked_add_with_arr(i8, -other.value,
+                                              arr_mask=self._isnan)
                 result = self._maybe_mask_results(result,
                                                   fill_value=libts.iNaT)
         else:

pandas/core/indexes/timedeltas.py

@@ -361,7 +361,8 @@ def _add_datelike(self, other):
         else:
             other = Timestamp(other)
             i8 = self.asi8
-            result = checked_add_with_arr(i8, other.value)
+            result = checked_add_with_arr(i8, other.value,
+                                          arr_mask=self._isnan)
             result = self._maybe_mask_results(result, fill_value=iNaT)
         return DatetimeIndex(result, name=self.name, copy=False)
 

pandas/tests/indexes/datetimelike.py

@@ -1,7 +1,11 @@
 """ generic datetimelike tests """
 
+import pytest
+
+import pandas as pd
 from .common import Base
 import pandas.util.testing as tm
+from pandas import Timestamp, Timedelta, NaT
 
 
 class DatetimeLike(Base):
@@ -38,3 +42,190 @@ def test_view(self, indices):
         i_view = i.view(self._holder)
         result = self._holder(i)
         tm.assert_index_equal(result, i_view)
+
+
+class TestDatetimeLikeIndexArithmetic(object):
+    # GH17991 checking for overflows and NaT masking on arithmetic ops
+
+    # TODO: Fill out the matrix of allowed arithmetic operations:
+    #   - __rsub__, __radd__
+    #   - ops with scalars boxed in Index/Series/DataFrame/np.array
+    #   - ops with scalars:
+    #              NaT, Timestamp.min/max, Timedelta.min/max
+    #              datetime, timedelta, date(?),
+    #              relativedelta,
+    #              np.datetime64, np.timedelta64,
+    #              DateOffset,
+    #              Period
+    #   - timezone-aware variants
+    #   - object-dtype, categorical dtype
+    #   - PeriodIndex
+    #   - consistency with .map(...) ?
+
+    def test_timedeltaindex_add_timestamp_nat_masking(self):
+        tdinat = pd.to_timedelta(['24658 days 11:15:00', 'NaT'])
+
+        # tsneg.value < 0, tspos.value > 0
+        tsneg = Timestamp('1950-01-01')
+        tspos = Timestamp('1980-01-01')
+
+        res1 = tdinat + tsneg
+        assert res1[1] is NaT
+        res2 = tdinat + tspos
+        assert res2[1] is NaT
+
+    def test_timedeltaindex_sub_timestamp_nat_masking(self):
+        tdinat = pd.to_timedelta(['24658 days 11:15:00', 'NaT'])
+
+        # tsneg.value < 0, tspos.value > 0
+        tsneg = Timestamp('1950-01-01')
+        tspos = Timestamp('1980-01-01')
+
+        res1 = tdinat - tsneg
+        assert res1[1] is NaT
+        res2 = tdinat - tspos
+        assert res2[1] is NaT
+
+    def test_timedeltaindex_add_timestamp_overflow(self):
+        tdimax = pd.to_timedelta(['24658 days 11:15:00', Timedelta.max])
+        tdimin = pd.to_timedelta(['24658 days 11:15:00', Timedelta.min])
+
+        # tsneg.value < 0, tspos.value > 0
+        tsneg = Timestamp('1950-01-01')
+        tspos = Timestamp('1980-01-01')
+
+        res1 = tdimax + tsneg
+        assert res1[1].value == Timedelta.max.value + tsneg.value
+        res2 = tdimin + tspos
+        assert res2[1].value == Timedelta.min.value + tspos.value
+
+        with pytest.raises(OverflowError):
+            tdimax + tspos
+
+        with pytest.raises(OverflowError):
+            tdimin + tsneg
+
+    def test_timedeltaindex_add_timedelta_overflow(self):
+        tdimax = pd.to_timedelta(['24658 days 11:15:00', Timedelta.max])
+        tdimin = pd.to_timedelta(['24658 days 11:15:00', Timedelta.min])
+
+        # tdpos.value > 0, tdneg.value < 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        with pytest.raises(OverflowError):
+            tdimax + tdpos
+
+        res2 = tdimax + tdneg
+        assert res2[1].value == Timedelta.max.value + tdneg.value
+        res3 = tdimin + tdpos
+        assert res3[1].value == Timedelta.min.value + tdpos.value
+
+        with pytest.raises(OverflowError):
+            tdimin + tdneg
+
+    def test_timedeltaindex_sub_timedelta_overflow(self):
+        tdimax = pd.to_timedelta(['24658 days 11:15:00', Timedelta.max])
+        tdimin = pd.to_timedelta(['24658 days 11:15:00', Timedelta.min])
+
+        # tdpos.value > 0, tdneg.value < 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        res1 = tdimax - tdpos
+        assert res1[1].value == Timedelta.max.value - tdpos.value
+
+        with pytest.raises(OverflowError):
+            tdimax - tdneg
+
+        with pytest.raises(OverflowError):
+            tdimin - tdpos
+
+        res4 = tdimin - tdneg
+        assert res4[1].value == Timedelta.min.value - tdneg.value
+
+    def test_datetimeindex_add_nat_masking(self):
+        # Checking for NaTs and checking that we don't get an OverflowError
+        dtinat = pd.to_datetime(['now', 'NaT'])
+
+        # tdpos.value > 0, tdneg.value < 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        res1 = dtinat + tdpos
+        assert res1[1] is NaT
+        res2 = dtinat + tdneg
+        assert res2[1] is NaT
+
+    def test_datetimeindex_sub_nat_masking(self):
+        # Checking for NaTs and checking that we don't get an OverflowError
+        dtinat = pd.to_datetime(['now', 'NaT'])
+
+        # tdpos.value > 0, tdneg.value < 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        res1 = dtinat - tdpos
+        assert res1[1] is NaT
+        res2 = dtinat - tdneg
+        assert res2[1] is NaT
+
+    def test_datetimeindex_add_timedelta_overflow(self):
+        dtimax = pd.to_datetime(['now', Timestamp.max])
+        dtimin = pd.to_datetime(['now', Timestamp.min])
+
+        # tdpos.value < 0, tdneg.value > 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        with pytest.raises(OverflowError):
+            dtimax + tdpos
+
+        res2 = dtimax + tdneg
+        assert res2[1].value == Timestamp.max.value + tdneg.value
+
+        res3 = dtimin + tdpos
+        assert res3[1].value == Timestamp.min.value + tdpos.value
+
+        with pytest.raises(OverflowError):
+            dtimin + tdneg
+
+    def test_datetimeindex_sub_timedelta_overflow(self):
+        dtimax = pd.to_datetime(['now', Timestamp.max])
+        dtimin = pd.to_datetime(['now', Timestamp.min])
+
+        # tdpos.value < 0, tdneg.value > 0
+        tdpos = Timedelta('1h')
+        tdneg = Timedelta('-1h')
+
+        res1 = dtimax - tdpos
+        assert res1[1].value == Timestamp.max.value - tdpos.value
+
+        with pytest.raises(OverflowError):
+            dtimax - tdneg
+
+        with pytest.raises(OverflowError):
+            dtimin - tdpos
+
+        res4 = dtimin - tdneg
+        assert res4[1].value == Timestamp.min.value - tdneg.value
+
+    def test_datetimeindex_sub_timestamp_overflow(self):
+        dtimax = pd.to_datetime(['now', Timestamp.max])
+        dtimin = pd.to_datetime(['now', Timestamp.min])
+
+        # tsneg.value < 0, tspos.value > 0
+        tsneg = Timestamp('1950-01-01')
+        tspos = Timestamp('1980-01-01')
+
+        with pytest.raises(OverflowError):
+            dtimax - tsneg
+
+        res2 = dtimax - tspos
+        assert res2[1].value == Timestamp.max.value - tspos.value
+
+        res3 = dtimin - tsneg
+        assert res3[1].value == Timestamp.min.value - tsneg.value
+
+        with pytest.raises(OverflowError):
+            dtimin - tspos