API: joining DatetimeIndexes not preserving freq

[jbrockmendel]

dti = pd.date_range('2016-01-01', periods=10)
left, right = dti[:5], dti[5:]
joined = left.join(right, how="outer")

In master joined.freq comes back as None, while in 0.25.3 it was "D". There is some code in DatetimeIndex._wrap_joined_index that suggests to me this was intentional.

Can someone confirm this suspicion cc @jorisvandenbossche ? If so, I've got a branch that restores the old behavior, just need to add tests.

[jorisvandenbossche]

There is some code in DatetimeIndex._wrap_joined_index that suggests to me this was intentional.

Do you mean it was intentionally preserving the freq, or that it was an intentional change in 1.0 to no longer preserve this?

[jbrockmendel]

Do you mean it was intentionally preserving the freq, or that it was an intentional change in 1.0 to no longer preserve this?

_wrap_joined_index looks like it was written to intentionally preserve the freq.