Following on from Collin, another ticket that generated a large amount of code churn for little perceived benefit was https://code.djangoproject.com/ticket/21127 (enforce on_delete). I know there are many in the community that rail against any and all changes (I had an argument with such a person on the 2.0 reddit thread recently), but we should endeavour to make churn as painless and infrequent as possible. As a concrete example with the on_delete ticket, we could have used settings to control the default on_delete behaviour per nullable and non-nullable foreign key. I know we don't like adding extra settings, and perhaps another path forward could have sufficed, but requiring everyone to update every foreign key definition is quite hostile.
In that light, I think a thread per deprecation on django-dev is a great idea, which will both help to keep us honest, and give those in the community that strongly dislike backward incompatible changes a chance to propose alternatives. I'm not so keen on the idea of keeping deprecations going for as long as Collin suggests. There should be little harm in 3rd party libraries declaring **this is the final version to support 1.8**, and then bumping the major version to support the next major Django series. The new LTS to LTS policy that Django has taken up is new - but should give 3rd party libraries a bit of certainty on how to support Django moving forward. The only concern I have is 3rd party libraries might begin to stop supporting versions of X.0 and X.1, and instead just support the LTS (X.2). That'll mean fewer users to run and test newer versions in production, if 3rd party ecosystem isn't keeping current. I don't know if that'll be an actual problem in practise though. I don't think it will be. For renames and moves, have we considered leaving around aliases indefinitely? How big is the overhead when the modules themselves are kept? We could generate an `ObsoleteWarning` + undocument to discourage usage. I don't wish to see or maintain large or complicated deprecations. At the same time, dropping renames seems like overkill. Could we maintain a catalog of renames in a single spot, then have the startup machinary patch old names? At least we'd avoid polluting the "real code" with shims. On Thursday, 7 December 2017 09:08:09 UTC+11, Tim Graham wrote: > > I don't see a strong reason to make it easy to support 1.8 and 2.0 at the > same time. Support for Django 1.8 ends 4 months after the release of 2.0. > As the 2.0 release notes say, "Following the release of Django 2.0, we > suggest that third-party app authors drop support for all versions of > Django prior to 1.11. At that time, you should be able to run your > package’s tests using python -Wd so that deprecation warnings do appear. > After making the deprecation warning fixes, your app should be compatible > with Django 2.0." > > Third-party packages aren't required to support a certain version of > Django until it's completely unsupported. In fact, a package dropping > support for a version of Django that's nearing it's end-of-life is a good > reminder for users to upgrade their Django. > > In the past few weeks, I sent a few pull requests to various third-party > packages following the "drop support for versions older than 1.11" > guideline and I thought this process was very clean. I'm not enthusiastic > about the idea of making the deprecation process even more lengthy. I think > it will mostly promote the continued use of deprecation features resulting > in messier code and encourage prolonged use of unsupported versions of > Django. > > Personally, I think asking developers to do a bit of house cleaning every > three years if you want to upgrade from LTS to then next LTS is reasonable. > What's your experience been like? > > On Wednesday, December 6, 2017 at 4:12:00 PM UTC-5, Collin Anderson wrote: >> >> Hi All, >> >> I think it would help if Django was better at *deprecations and backward >> compatibility*. I’ve brought this up [before >> <https://groups.google.com/d/msg/django-developers/ZWy2Esj46nE/jzSP3DRIEAAJ>], >> >> but didn’t get any feedback, so here’s another try at it, with some >> *specific >> ideas of how to improve things below*. >> >> *Background*: >> >> The [API docs <https://docs.djangoproject.com/en/2.0/misc/api-stability/>] >> say “*If, for some reason, an API declared stable must be removed or >> replaced*, it will be declared deprecated but will remain in the API for >> at least two feature releases.” - I’ve always thought of the “must be >> removed” as “there’s really no alternative”. I think that if it's not >> broken, Django should avoid breaking it. >> >> I maintain lots of Django projects, and upgrading is not a small task. >> There are enough changes to undocumented APIs already happening that it >> would be great if the documented ones didn't change as much. >> >> I also think it’s a little disappointing that *3rd party libraries don’t >> get easy 1.8 and 2.0 support out of the box*. Both of those releases are >> currently supported, but if the library uses deprecated features to support >> 1.8, it won’t work on 2.0 by definition. >> >> Yes, backward compatibility means Django has more technical debt, and yes >> it comes at a cost (more code, more docs, tests run longer, more thank-less >> maintenance etc), but it means Django’s not forcing users to do the tedious >> work of changing their code. That’s a _huge_ benefit. Isn’t the whole point >> of a framework to have documented and tested code so the user doesn’t need >> to do tedious things? “it takes care of much of the hassle of Web >> development, so you can focus on writing your app.” >> >> Some deprecations I thought could have gone better: #17209 (auth views), >> #26013 (urls.urlresolvers), #22218 (url patterns()), #23276 (url() >> strings), #14675 (urls.defaults), #6735 (views.generic.simple), #18651 >> (assignment_tag). >> >> *Ideas of how to improve backward compatibility*: >> >> *1.* I think it would help if any breaking change, and any new >> deprecation/removal (any change that adds to those sections in the release >> notes) received 3-7 days *feedback from the mailing list*, with a clear >> subject, something like “deprecating X”, "changing x's defaults", “renaming >> X” or “removing X”. It's a little more bureaucracy, but I think there's a >> huge benefit to making sure everyone's on the same page about these things. >> (This already happens for some, but not all deprecations.) >> >> I don’t pay close attention to tickets and pull requests, so I often >> don’t notice that there’s a new deprecation/removal until _after_ it’s >> already been merged. The few people on the ticket may have agreed to >> removing something, but not necessarily the larger community. Or, if it was >> being discussed, a lot of discussion was on the new feature, and it wasn’t >> clear that a deprecation/removal would be included in the change. >> (Sometimes the deprecation is thrown in as an after-thought / "while we're >> at it, lets rename...") >> >> Having a *clear email in django-developers* would also give more people >> the initial heads-up to avoid using the old code. >> >> *2.* For some changes, Django has decided to delay/*hold off >> deprecating/removing a feature until after the next LTS or “eventually”* >> (some good examples: #23433 (django-admin.py), #27753 (utils.six, etc), >> #25236 (ifequal), #25978 (render_to_response), #28593 (url() -> re_path()). >> I think this delay is a really good thing, and I think it should be *more >> official/documented to encourage its use* (if not the default). As [Russ >> put it >> <https://groups.google.com/d/msg/django-developers/J7vpMKSHk7U/3vGPs71MCgAJ> >> ]: >> >> “The only other suggestion I've got is to add a new "pre-deprecation" >> step to our deprecation process - a flag that lets us indicate that at some >> point, we intend to deprecate something, but we haven't decided when that >> will be. This would essentially be a "*don't use this on new code, but >> there's no rush in replacing it*". It could also be accompanied with a >> Warning so that existing uses could be found and replaced if someone was so >> inclined.” >> >> Delaying the removal would *help libraries support both 1.8 and 2.0* >> (for example) at the same time. (Also, I think a longer removal timeline >> might make it a little less likely for something to be deprecated/removed >> in the first place. - A good thing, in my opinion.) >> >> Thanks, >> Collin >> >> [before] >> https://groups.google.com/d/msg/django-developers/ZWy2Esj46nE/jzSP3DRIEAAJ >> >> [API docs] https://docs.djangoproject.com/en/2.0/misc/api-stability/ >> >> [Russ put it] >> https://groups.google.com/d/msg/django-developers/J7vpMKSHk7U/3vGPs71MCgAJ >> >> -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/django-developers. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/4d1fc6c3-d156-4458-b5c6-904542028aea%40googlegroups.com. 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