BUG: TDI.insert with empty TDI raising IndexError

pandas/core/indexes/datetimelike.py

@@ -2,7 +2,7 @@
 Base and utility classes for tseries type pandas objects.
 """
 import operator
-from typing import List, Optional, Set
+from typing import List, Optional, Set, Union
 
 import numpy as np
 
@@ -30,8 +30,8 @@
 from pandas.core.accessor import PandasDelegate
 from pandas.core.arrays import (
     DatetimeArray,
-    ExtensionArray,
     ExtensionOpsMixin,
+    PeriodArray,
     TimedeltaArray,
 )
 from pandas.core.arrays.datetimelike import (
@@ -96,7 +96,7 @@ class DatetimeIndexOpsMixin(ExtensionIndex, ExtensionOpsMixin):
     Common ops mixin to support a unified interface datetimelike Index.
     """
 
-    _data: ExtensionArray
+    _data: Union[DatetimeArray, TimedeltaArray, PeriodArray]
     freq: Optional[DateOffset]
     freqstr: Optional[str]
     _resolution: int
@@ -950,7 +950,7 @@ class DatetimelikeDelegateMixin(PandasDelegate):
     _raw_methods: Set[str] = set()
     # raw_properties : dispatch properties that shouldn't be boxed in an Index
     _raw_properties: Set[str] = set()
-    _data: ExtensionArray
+    _data: Union[DatetimeArray, TimedeltaArray, PeriodArray]
 
     def _delegate_property_get(self, name, *args, **kwargs):
         result = getattr(self._data, name)

pandas/core/indexes/datetimes.py

@@ -907,7 +907,7 @@ def inferred_type(self) -> str:
         # sure we can't have ambiguous indexing
         return "datetime64"
 
-    def insert(self, loc, item):
+    def insert(self, loc: int, item):
         """
         Make new Index inserting new item at location
 
@@ -933,10 +933,9 @@ def insert(self, loc, item):
 
         freq = None
 
-        if isinstance(item, (datetime, np.datetime64)):
-            self._assert_can_do_op(item)
-            if not self._has_same_tz(item) and not isna(item):
-                raise ValueError("Passed item and index have different timezone")
+        if isinstance(item, self._data._recognized_scalars) or item is NaT:
+            item = self._data._scalar_type(item)
+            self._data._check_compatible_with(item, setitem=True)
 
             # check freq can be preserved on edge cases
             if self.size and self.freq is not None:
@@ -946,7 +945,7 @@ def insert(self, loc, item):
                     freq = self.freq
                 elif (loc == len(self)) and item - self.freq == self[-1]:
                     freq = self.freq
-            item = _to_M8(item, tz=self.tz)
+            item = item.asm8
 
         try:
             new_dates = np.concatenate(

pandas/core/indexes/period.py

@@ -732,7 +732,7 @@ def _convert_tolerance(self, tolerance, target):
             raise ValueError("list-like tolerance size must match target index size")
         return self._maybe_convert_timedelta(tolerance)
 
-    def insert(self, loc, item):
+    def insert(self, loc: int, item):
         if not isinstance(item, Period) or self.freq != item.freq:
             return self.astype(object).insert(loc, item)
 

pandas/core/indexes/timedeltas.py

@@ -381,7 +381,7 @@ def is_type_compatible(self, typ) -> bool:
     def inferred_type(self) -> str:
         return "timedelta64"
 
-    def insert(self, loc, item):
+    def insert(self, loc: int, item):
         """
         Make new Index inserting new item at location
 
@@ -409,15 +409,19 @@ def insert(self, loc, item):
             )
 
         freq = None
-        if isinstance(item, Timedelta) or (is_scalar(item) and isna(item)):
+        if isinstance(item, self._data._recognized_scalars) or item is NaT:
+            item = self._data._scalar_type(item)
+            self._data._check_compatible_with(item, setitem=True)
 
             # check freq can be preserved on edge cases
-            if self.freq is not None:
-                if (loc == 0 or loc == -len(self)) and item + self.freq == self[0]:
+            if self.size and self.freq is not None:
+                if item is NaT:
+                    pass
+                elif (loc == 0 or loc == -len(self)) and item + self.freq == self[0]:
                     freq = self.freq
                 elif (loc == len(self)) and item - self.freq == self[-1]:
                     freq = self.freq
-            item = Timedelta(item).asm8.view(_TD_DTYPE)
+            item = item.asm8
 
         try:
             new_tds = np.concatenate(

pandas/tests/indexes/datetimes/test_indexing.py

@@ -411,9 +411,9 @@ def test_insert(self):
 
         # see gh-7299
         idx = date_range("1/1/2000", periods=3, freq="D", tz="Asia/Tokyo", name="idx")
-        with pytest.raises(ValueError):
+        with pytest.raises(TypeError):
             idx.insert(3, pd.Timestamp("2000-01-04"))
-        with pytest.raises(ValueError):
+        with pytest.raises(TypeError):
             idx.insert(3, datetime(2000, 1, 4))
         with pytest.raises(ValueError):
             idx.insert(3, pd.Timestamp("2000-01-04", tz="US/Eastern"))

pandas/tests/indexes/timedeltas/test_indexing.py

@@ -161,6 +161,15 @@ def test_take_fill_value(self):
 
 
 class TestTimedeltaIndex:
+    def test_insert_empty(self):
+        # Corner case inserting with length zero doesnt raise IndexError
+        idx = timedelta_range("1 Day", periods=3)
+        td = idx[0]
+
+        idx[:0].insert(0, td)
+        idx[:0].insert(1, td)
+        idx[:0].insert(-1, td)
+
     def test_insert(self):
 
         idx = TimedeltaIndex(["4day", "1day", "2day"], name="idx")

pandas/tests/indexing/test_coercion.py

@@ -432,13 +432,19 @@ def test_insert_index_datetimes(self, fill_val, exp_dtype):
         )
         self._assert_insert_conversion(obj, fill_val, exp, exp_dtype)
 
-        msg = "Passed item and index have different timezone"
         if fill_val.tz:
-            with pytest.raises(ValueError, match=msg):
+            msg = "Cannot compare tz-naive and tz-aware datetime-like objects"
+            with pytest.raises(TypeError, match=msg):
                 obj.insert(1, pd.Timestamp("2012-01-01"))
 
-        with pytest.raises(ValueError, match=msg):
-            obj.insert(1, pd.Timestamp("2012-01-01", tz="Asia/Tokyo"))
+            msg = "Timezones don't match"
+            with pytest.raises(ValueError, match=msg):
+                obj.insert(1, pd.Timestamp("2012-01-01", tz="Asia/Tokyo"))
+
+        else:
+            msg = "Cannot compare tz-naive and tz-aware datetime-like objects"
+            with pytest.raises(TypeError, match=msg):
+                obj.insert(1, pd.Timestamp("2012-01-01", tz="Asia/Tokyo"))
 
         msg = "cannot insert DatetimeIndex with incompatible label"
         with pytest.raises(TypeError, match=msg):