(From master)
import pandas as pd
idx = pd.to_datetime(["2020-01-01", None])
idx.map(lambda x: pd.Timestamp("1999-01-01"), na_action="ignore")
# DatetimeIndex(['1999-01-01', '1999-01-01'], dtype='datetime64[ns]', freq=None)
idx = pd.CategoricalIndex(["a", None], categories=["a"])
idx.map(lambda x: x, na_action="ignore")
# TypeError: map() got an unexpected keyword argument 'na_action'
In the DatetimeIndex case idx.map should propagate the null value instead of returning Timestamp("1999-01-01") since na_action == "ignore", and although it isn't documented I think CategoricalIndex.map should allow na_action since the other map methods do.
Comment From: topper-123
The DateTimeIndex case has been fixed in #51936.
The Categorical case will be fixed when #51645 is merged.
Comment From: topper-123