[Python-Dev] Are undocumented exceptions considered bugs?

[Stefan Bucur]

Hi,

I'm not sure this is the right place to ask this question, but I thought
I'd give it a shot since it also concerns the Python standard library.

I'm writing an automated test case generation tool for Python programs that
explores all possible execution paths through a program. When applying this
tool on Python's 2.7.3 urllib package, it discovered input strings for
which the urllib.urlopen(url) call would raise a TypeError. For instance:

urllib.urlopen('\x00\x00\x00')

[...]
  File "/home/bucur/onion/python-bin/lib/python2.7/urllib.py", line 86, in
urlopen
    return opener.open(url)
  File "/home/bucur/onion/python-bin/lib/python2.7/urllib.py", line 207, in
open
    return getattr(self, name)(url)
  File "/home/bucur/onion/python-bin/lib/python2.7/urllib.py", line 462, in
open_file
    return self.open_local_file(url)
  File "/home/bucur/onion/python-bin/lib/python2.7/urllib.py", line 474, in
open_local_file
    stats = os.stat(localname)
TypeError: must be encoded string without NULL bytes, not str

In the urllib documentation it is only mentioned that the IOError is raised
when the connection cannot be established. Since the input passed is a
string (and not some other type), is the TypeError considered a bug (either
in the documentation, or in the implementation)?

Thanks a lot,
Stefan
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