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ftpfs possible issue with openbin #406
Description
Recently, while trying out the ftpfs, I've noticed that to open a binary file-like object for writing by some third-party packages I have to do this:
with open_fs("ftp://anonymous:anonymous@localhost:8021") as fs:
with fs.openbin("test.bin", "wb") as f:
...
Note in the above the mode param used in openbin includes b: Looking at the docs for the mode param it suggests the b is implied via openbin, but b isn't implicitly added to the mode of the file-like that is returned by openbin - this means that, unless b is explicitly provided as above, third-party packages that inspect the mode of the file-like may complain that it is not opened in binary mode.
Should openbin not reflect the implied b by implicitly adding b to the mode?
Activity
lurch commentedon Jun 24, 2020
Yeah, perhaps FTPFS should also be doing this? https://github.com/PyFilesystem/pyfilesystem2/blob/master/fs/osfs.py#L360
al8ba commentedon Jun 24, 2020
Yes, I was thinking of mentioning use of
to_platform_binin a similar manner.I guess another way of putting the question is that, given the "
bis implied byopenbin" in the docs, then for a filefopened via it should"b" in f.modehold true? Sounds almost like a unit test...willmcgugan commentedon Jun 24, 2020
The base class only guarantees that
openbinwill return a BinaryIO, which doesn't contain a "mode" attribute. Only theio.FileIOclass can be sure of having mode.So it would be a mistake to assume that all file-like objects have a "mode" attribute. But people do write broken code because they make reasonable assumptions and the specifications are too difficult to understand, so perhaps it would be a good idea for ftp files to add a mode attribute.
al8ba commentedon Jun 24, 2020
The
FTPFileobject does have a mode attribute - the issue I'm bringing up is that if theFTPFileinstance comes from a call toopenbinthen the mode within it will not containb, unlessbwas explicitly supplied in the call toopenbin.I think a solution to this, similar to the previous note about osfs, would be to have the final two lines of
openbinlook more akin to this:althonos commentedon Oct 13, 2020
Actually, it is reasonable to expect
FS.openbinto return an object with amodeattribute (containing a "b" flag), since it all filesystems are doing it butFTPFileand_MemoryFile. I patched them in #435