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

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.unpack_archive() 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 unpack_archive 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.unpack_archive
>> 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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