BUG: bug in json lib when frame has length zero

[behzadnouri]

closes #9781

on master:

>>> df = DataFrame(columns=['jim', 'joe'])
>>> df
Empty DataFrame
Columns: [jim, joe]
Index: []
>>> df.to_json()
'{}'

mixed type will segfault:

>>> df['joe'] = df['joe'].astype('i8')
>>> df.to_json()
Segmentation fault (core dumped)

on branch:

>>> df.to_json()
'{"jim":{},"joe":{}}'
>>> df['joe'] = df['joe'].astype('i8')
>>> read_json(df.to_json())
Empty DataFrame
Columns: [jim, joe]
Index: []

[shoyer]

Awesome, thanks!

[behzadnouri]

@shoyer i am not sure this actually closes #9781

this handles the case in the comments but the OP's issue may still persists.

[shoyer]

OK, that may have been a bit premature :).

[shoyer]

can you test your new code on that pickle file?

[dashesy]

I hit this error in 0.16.0