BUG: fix AttributeError raised with pd.concat between a None and timezone-aware Timestamp

[yuanx749]

Take over #53042. I updated the test. It should produce a FutureWarning.

• closes BUG: AttributeError raised with pd.concat between a None and Timestamp #52093 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[jbrockmendel]

we need to be sure that the Timestamp here has the same unit as the dtype

[yuanx749]

I added the unit.

Is this function only for NA fill_value? Then it seems unit has no effect since NaT does not have unit.

[jbrockmendel]

Its always NA for concat, but we can get here with non-NA via reindex with fill_vlaue

[yuanx749]

I notice something weird in the test for reindex with fill_value below.

pandas/pandas/tests/frame/methods/test_reindex.py

Lines 139 to 148 in 14a6c9a

	def test_reindex_tzaware_fill_value(self):
	# GH#52586
	df = DataFrame([[1]])
	ts = pd.Timestamp("2023-04-10 17:32", tz="US/Pacific")
	res = df.reindex([0, 1], axis=1, fill_value=ts)
	assert res.dtypes[1] == pd.DatetimeTZDtype(unit="s", tz="US/Pacific")
	expected = DataFrame({0: [1], 1: [ts]})
	expected[1] = expected[1].astype(res.dtypes[1])
	tm.assert_frame_equal(res, expected)

Though the test passes, the representation seems weird. print(res) shows,

   0                                   1
0  1 1969-12-31 16:00:01.681173120-08:00

while it should be as print(expected):

   0                         1
0  1 2023-04-10 17:32:00-07:00

It seems DatetimeArray only works when unit is 'ns'. Could you have a further look? @jbrockmendel

pandas/pandas/core/internals/managers.py

Lines 2298 to 2302 in 14a6c9a

	def make_na_array(dtype: DtypeObj, shape: Shape, fill_value) -> ArrayLike:
	if isinstance(dtype, DatetimeTZDtype):
	# NB: exclude e.g. pyarrow[dt64tz] dtypes
	i8values = np.full(shape, fill_value._value)
	return DatetimeArray(i8values, dtype=dtype)

[github-actions]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

[mroeschke]

Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.

[yuanx749]

Still waiting for requested review, any update needed from my side?

[jbrockmendel]

This looks good to me. can you move the whatsnew note to 2.2

[yuanx749]

This looks good to me. can you move the whatsnew note to 2.2

Thanks. I've moved the note.

[mroeschke]

Thanks @yuanx749