mostawesomedude / betterpath Goto Github PK

It seems that the FilePath you get by calling temporarySibling() can only be used once. I discovered this while trying to use that as a way to download a file into a temporary name, then rename it into the final destination name so that other programs reading that file would see either the old or new contents, not an intermediate state (since moveTo() tries very hard to be atomic).

Here's a small script which demonstrates the bug:

from bp.filepath import FilePath

path = FilePath("/tmp/whatever")
tmp = path.temporarySibling()
with tmp.open("w") as fp:
    fp.write("Hello, world\n")

with tmp.open("r") as fp:
    print fp.read()

Which results in the following error:

Traceback (most recent call last):
  File "betterpath_bug.py", line 8, in <module>
    with tmp.open("r") as fp:
  File "/Users/dcrosta/.../bp/filepath.py", line 438, in open
    return self.create()
  File "/Users/dcrosta/.../bp/filepath.py", line 1012, in create
    fdint = os.open(self.path, _CREATE_FLAGS)
OSError: [Errno 17] File exists: '/tmp/EfvvV6szVDBZfPlkwhatever'

In the traceback you can see it's calling create() even though I'm trying to do a read operation?

You get the same error if you try to re-open the file with mode "w", too.

Can I coax you into another release (containing the context manager for MemoryFile)?