TST: Fix makeObjectSeries data as object type

[jmg7173]

• closes tm.makeObjectSeries returns a Series with dtype="datetime64[ns]" #28378
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[WillAyd]

Cool this looks good. Any chance you looked at where this was ultimately used? Would be nice to clean up any casting that this required in the past

[jmg7173]

Umm, there is no casting about this.

One thing that I can doubt is usage on test_objarr_add_invalid. Because it tested about add and sub operation on object that made by datetime64[ns].
It is at pandas/tests/arithmetic/test_object.py L144.

Other things are used just representing a series made by object as I summarized at #28378.

Can you tell me more details about what should I do?

And should I add an entry at whatsnew on v1.0?

[WillAyd]

One thing that I can doubt is usage on test_objarr_add_invalid. Because it tested about add and sub operation on object that made by datetime64[ns].
It is at pandas/tests/arithmetic/test_object.py L144.

Yea that's a great find - thanks for being thorough. Can you see where that was introduced to see what the intention was? The fact that it blanket catches an Exception is a little bit of a red flag as to the intent.

Also looking these over I'm surprised that all of the makeABCSeries methods don't actually make a series of dtype ABC, but instead just contain an index of dtype ABC. Do you have any thoughts on how those methods are comprehensively used?

[jmg7173]

Can you see where that was introduced to see what the intention was?

Although I can't find origin of test_objarr_add_invalid, but it's intention was raising error on numerical operator about datetime64[ns] like object. Here's my reference(91ee418). I can't find more deeply because file was deleted.(pandas/tests/test_series.py)

pandas/pandas/tests/series/test_operators.py

Lines 187 to 195 in 91ee418

	def test_operators_timedelta64(self):
	# invalid ops
	self.assertRaises(Exception, self.objSeries.__add__, 1)
	self.assertRaises(Exception, self.objSeries.__add__,
	np.array(1, dtype=np.int64))
	self.assertRaises(Exception, self.objSeries.__sub__, 1)
	self.assertRaises(Exception, self.objSeries.__sub__,
	np.array(1, dtype=np.int64))

So, test would be modified as datetime64[ns] converted to base object.

Also looking these over I'm surprised that all of the makeABCSeries methods don't actually make a series of dtype ABC, but instead just contain an index of dtype ABC.

Yes, only makeObjectSeries returns a series that contains dtype=object... It is so weird. I think makeObjectSeries do correct job and other things are not. I think every makeABCSeries should return dtype=ABC with default index. What do you expect as exact result of makeABCSeries?

Do you have any thoughts on how those methods are comprehensively used?

About that, it's too hard question to me :)

[WillAyd]

I think makeObjectSeries do correct job and other things are not. I think every makeABCSeries should return dtype=ABC with default index.

Yea that seems logical to me though doesn't appear to be the case. cc @jreback in case of any historical knowledge as to why things are that way

[jreback]

thanks @jmg7173

yeah we likely have enough testing already in place.