[Python-Dev] Soliciting comments on the future of the cmdmodule (bpo-33233)

[Brett Cannon]

On Sat, 7 Apr 2018 at 02:09 Steven D'Aprano <steve at pearwood.info> wrote:

> On Sat, Apr 07, 2018 at 09:30:05AM +0100, Paul Moore wrote:
> > On 7 April 2018 at 04:13, Steve Dower <steve.dower at python.org> wrote:
> > > Better to deprecate it before it becomes broken, in my opinion.
>
> That argument could be applied to everything in the std lib.
>

Sure, but we all know none of this is as black-and-white as it's being
portrayed either.


>
>
> > > Having someone willing and able to review and merge changes is the best
> > > criteria for whether a module is still supported or not.
>
> I don't think "best" is justified -- and certainly it is not the *only*
> criteria.
>

But you have to admit it is an important one.


>
> Modules can become stable simply because they have no known bugs and no
> new feature requests. Stable doesn't mean useless, and the urge to
> consider anything that isn't being regularly fiddled with as "obsolete"
> is a tendency to be resisted.
>
> If the module isn't broken, there's no need to fix it. That's a GOOD
> thing, not a reason to dump a perfectly good, useful, working module.
>

I think part of the question is whether the module is also used enough to
justify putting in scarce core dev time to maintain it.


>
> Raymond has stated that he is happy to work on it if there are any bugs
> reported on it, and if he's not available, I'm sure somebody will.


Actually Raymond said he *teaches* the module, not that he wanted to
maintain it. And I definitely would not assume that someone will pick up to
help maintain any module in the stdlib.


> And
> if not, well, we don't have any sort of performance guarantees on fixes:
> sooner or later, *somebody* will provide a patch.


Assuming someone does, do we really want to say, "eh, it's buggy but we can
wait over 7 years for a fix" (the oldest open issue on b.p.o is from August
2009: https://bugs.python.org/issue6686). And even if they do, that doesn't
mean someone will have the time or inclination to review it and eventually
see it through to being merged.


> That's the beauty of
> the Open Source model. There are plenty of potential upstream
> contributors who could contribute a patch.
>

But potential does not necessarily translate to action.


>
>
> > I think there's a difference between not being willing to add
> > enhancements, and not fixing bugs. The issue that originally triggered
> > this discussion was an enhancement request, and I don't think it's
> > unreasonable to declare cmd as "stable - no further enhancements will
> > be made or accepted" while still considering it as supported for
> > bugfixes.
>
> Its not an unreasonable position to take, but I don't think it is
> justified in this case. The cmd module is not something so arcane or
> complicated that it requires a specialist to maintain it. Its about 400
> lines, including blank lines and doc strings, with a single class and
> around twenty methods.
>
> Wasn't one of the major reasons for moving to git and Github to
> make it easier for non-core devs to contribute?


Actually the major reason was to make it easier for core devs to review
contributions. Easing the workflow for outside contributors was a side
benefit.


> A module as stable and
> simple as cmd seems to me to be the ideal place for people to begin
> contributing, whether it is fixing bugs or contributing any
> (hypothetical) feature enhancements.
>

Perhaps, but that assumes someone wants that job. ;)


>
> I don't think we need do anything here: so long as there is a core
> developer willing to review any PRs, and so long as new enhancements go
> through the same approval process on the bug tracker and/or Python-
> Ideas, I don't think we need to single cmd out as deprecated or "no new
> features".
>

Those two "so long as" parts are I think the key reason Ned brought this up.


>
> This isn't gopher, or something with serious unfixable security
> vulnerabilities. It works. What more needs to be said?
>

I think this all ties back to the usual discussion we have when it comes to
the stdlib: what  is the bar for what should be in there because nothing is
maintenance-free?

The cmd module itself has plenty of commits that were just standard code
maintenance changes:
https://github.com/python/cpython/commits/master/Lib/cmd.py . All of that
eats up time over the 26 years of the module's existence. And feature
enhancements are not free either even if you don't review the PR because
even if you don't review them you still have to peruse the PR title to make
the decision not to review it, which once again is a small amount of time
in isolation but adds up at a macro level.

We all have a limited amount of time to contribute, especially when we are
almost all spending personal time on this project. And no matter how
trivial a module is to keep around, it is not a non-zero amount of time for
the group all-up, even if we all collectively choose to ignore it in hopes
someone comes forward to help out.

And I would also say that ignoring a module until someone comes forward to
maintain it runs counter-productive to our overall goal to produce quality
software as we are effectively saying we are okay with lower quality if it
simply puts us out too much to maintain it. I personally would argue that
the language itself is an amazingly solid piece of software but that the
stdlib's quality varies. For me, that's where my personal desire to trim
the stdlib a bit so we can have "more wood behind fewer arrows" and bring
the stdlib's quality up a bit.
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