[Python-Dev] Is adding support for os.PathLike an enhancement or bugfix? (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed May 3 21:19:02 EDT 2017

On 5/3/2017 7:13 PM, Koos Zevenhoven wrote:

On Thu, May 4, 2017 at 1:07 AM, Terry Reedy <tjreedy at udel.edu> wrote:

On 5/3/2017 2:15 PM, Brett Cannon wrote:

My allergies have hit me hard so I'm not thinking at full capacity, but did we ever decide if supporting os.PathLike in the stdlib was viewed as an enhancement or bugfix? Specifically I'm thinking of https://bugs.python.org/issue30218 for adding support to shutil.unpackarchive() and whether it should be backported to 3.6. On the face of it, that particular issue looks like an enhancement that should have gone into 3.6 Agreed. (if ever), but did not. I notice that https://www.python.org/dev/peps/pep-0519/#implementation did not include "Update shutil", so it was not done, at least not completely. Shutil was among the most important to be updated, IMO. I had made some sort of list of affected modules elsewhere [1]: ntpath, posixpath, os.scandir, os.[other stuff], DirEntry (tempted to say os.DirEntry, but that is not true), shutil.[stuff], (io.)open, fileinput, filecmp, zipfile, tarfile, tempfile (for the 'dir' keyword arguments), maybe even glob and fnmatch (are the patterns paths?)

What did not get done for 3.6 should be proposed for 3.7.

It looks like what made it to PEP519 was mainly this:

"It is expected that most APIs in Python's standard library that currently accept a file system path will be updated appropriately to accept path objects (whether that requires code or simply an update to documentation will vary)."

To me that says that not being updated (yet) is not a bug.

Was shutil updated at all? Is unpackarchive the only shutil function not updated? If so, I could see the omission as a bug.

If the patch for 30218 were applied in 3.6, would the doc https://docs.python.org/3/library/shutil.html#shutil.unpackarchive need to be changed, with a note "Added in 3.6.2: filename can be any pathlike object"? If so, it is an enhancement. Regardless of bugfix vs enhancement semantics, that seems like a good thing to do.

Enhancing public APIs in normal (non-provisional) modules in bugfix releases has turned out to be a bad thing to do. Hence the policy to not do that. The few exceptions have been necessary to fix a bug that needed to be fixed, and could not reasonably be fixed otherwise.

[1] e.g. in this thread somewhere: https://mail.python.org/pipermail/python-ideas/2016-April/039827.html

-- Terry Jan Reedy

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