BUG: preserve the dtype on Series.combine_first

[jessestone7]

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Reproducible Example

import pandas as pd

pd.Series([4, 5]).combine_first(pd.Series([6, 7, 8]))
0    4.0
1    5.0
2    8.0
dtype: float64

pd.Series([4, 5]).to_frame().combine_first(pd.Series([6, 7, 8]).to_frame())[0]
0    4
1    5
2    8
Name: 0, dtype: int64

Issue Description

In issue #39051 DataFrame.combine_first was fixed to preserve type. The problem still exists for Series.combine_first however. In the example here, int is converted to float when Series.combine_first is used, but not when DataFrame.combine_first is used.

Expected Behavior

Expected behavior:

pd.Series([4, 5]).combine_first(pd.Series([6, 7, 8]))
0 4
1 5
2 8
dtype: int64

Installed Versions

Pandas version 1.5.3

[lukemanley]

Thanks for the report. I agree this should preserve the dtype like the DataFrame method does.