🐛[BUG]: time averaging loses the time coordinate informations

[ChenggongWang]

Version

source - main

On which installation method(s) does this occur?

Source

Describe the issue

This bug is caused by code here and can be reproduced by following code.

import pandas as pd
import numpy as np
time = pd.date_range("2000-01-01", freq="h", periods=365 * 24)
ds = xr.Dataset({"foo": ("time", np.arange(365 * 24)), "time": time})
print('raw')
print(ds.time)
print('corrected resample')
print(ds.resample(time='1ME').mean(dim="time", keep_attrs=True, skipna=False).time)
print('current resample loses the time coordinate information')
print(ds.resample(time='1ME').mean(dim="time", keep_attrs=True, skipna=False, keepdims=True).time)

output

raw
 Size: 70kB
array(['2000-01-01T00:00:00.000000000', '2000-01-01T01:00:00.000000000',
       '2000-01-01T02:00:00.000000000', ..., '2000-12-30T21:00:00.000000000',
       '2000-12-30T22:00:00.000000000', '2000-12-30T23:00:00.000000000'],
      dtype='datetime64[ns]')
Coordinates:
  * time     (time) datetime64[ns] 70kB 2000-01-01 ... 2000-12-30T23:00:00
corrected resample
 Size: 96B
array(['2000-01-31T00:00:00.000000000', '2000-02-29T00:00:00.000000000',
       '2000-03-31T00:00:00.000000000', '2000-04-30T00:00:00.000000000',
       '2000-05-31T00:00:00.000000000', '2000-06-30T00:00:00.000000000',
       '2000-07-31T00:00:00.000000000', '2000-08-31T00:00:00.000000000',
       '2000-09-30T00:00:00.000000000', '2000-10-31T00:00:00.000000000',
       '2000-11-30T00:00:00.000000000', '2000-12-31T00:00:00.000000000'],
      dtype='datetime64[ns]')
Coordinates:
  * time     (time) datetime64[ns] 96B 2000-01-31 2000-02-29 ... 2000-12-31
current resample loses the time coordinate information
 Size: 96B
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11])
Dimensions without coordinates: time

Suggestion: keepdims=True should be removed.

Environment details

No response