REGR: 1.3 behavior change with groupby and asindex=False

Code Sample, a copy-pastable example

pd.DataFrame(columns=["date", "crew_member_id"])
    .groupby(["date", "crew_member_id"], as_index=False)
    .sum()

Problem description

With 1.3rc1 this fails with ValueError: Length of values (0) does not match length of index (1) while 1.2 returns and empty frame.

Expected Output

If this is the expected behavior fine. Just wanted to ensure that it is not an accidental regression.

[phofl]

This one fails too:

df = pd.DataFrame(columns=["a", "b"]).groupby(["a"], as_index=False).sum()

The initial code snippet seems a bit artificial to me, mostly because I don’t know what to actually expect. But this one returned

Empty DataFrame
Columns: [a, b]
Index: []

on 1.2.4 which looks sensible to me. Labelling as a regression

[rhshadrach]

Ah - this path is dropping column ‘b’ because it is object dtype. Doing

print(pd.DataFrame(columns=["a", "b"], dtype=int).groupby(["a"], as_index=False).sum())

gives

Empty DataFrame
Columns: [a, b]
Index: []

which is better. Running tests now, PR to follow.