to_csv fails silently with s3fs

[gpkc]

Code Sample, a copy-pastable example if possible

import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randint(0,100,size=(100, 4)), columns=list('ABCD'))
df.to_csv("s3://super_dumb_s3_bucket/not_real.csv")

Problem description

If you provide an invalid s3 path (e.g. a bucket that you don't have access to), this command fails silently.

Expected Output

Raise some exception at least.

Output of pd.show_versions()

[paste the output of pd.show_versions() here below this line]
INSTALLED VERSIONS

commit : None
python : 3.7.2.final.0
python-bits : 64
OS : Linux
OS-release : 4.15.0-88-generic
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : en_US.UTF-8

pandas : 0.25.1
numpy : 1.17.0
pytz : 2019.2
dateutil : 2.8.0
pip : 19.0.2
setuptools : 40.8.0
Cython : None
pytest : 3.10.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.4.1
html5lib : None
pymysql : None
psycopg2 : 2.8.3 (dt dec pq3 ext lo64)
jinja2 : 2.10.1
IPython : 7.9.0
pandas_datareader: None
bs4 : 4.8.0
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : 4.4.1
matplotlib : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
s3fs : None
scipy : 1.3.1
sqlalchemy : None
tables : None
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None

[TomAugspurger]

Hmm... thanks for the report.

I think the issue is the failure to call close in

pandas/pandas/io/formats/csvs.py

Lines 174 to 204 in 970499d

	if is_zip:
	# zipfile doesn't support writing string to archive. uses string
	# buffer to receive csv writing and dump into zip compression
	# file handle. GH21241, GH21118
	f = StringIO()
	close = False
	elif hasattr(self.path_or_buf, "write"):
	f = self.path_or_buf
	close = False
	else:
	f, handles = get_handle(
	self.path_or_buf,
	self.mode,
	encoding=self.encoding,
	compression=dict(self.compression_args, method=self.compression),
	)
	close = True
	try:
	# Note: self.encoding is irrelevant here
	self.writer = csvlib.writer(
	f,
	lineterminator=self.line_terminator,
	delimiter=self.sep,
	quoting=self.quoting,
	doublequote=self.doublequote,
	escapechar=self.escapechar,
	quotechar=self.quotechar,
	)
	self._save()

. S3FS only makes the request to validate the credentials when the file is actually closed, which we don't seem to do here.

Are you interested in debugging further?

[adamhadani]

👍 just ran into this myself. very dangerous silent failure..

[TomAugspurger]

See also #32470. Can anyone see if reverting the relevant changes in d6fe194#diff-a37b395bed03f0404dec864a4529c97d (at least for write mode) is doable?