[ckan-dev] Recommended practice for supporting both CKAN 1.8 and 2.0 in extensions

Fri Jan 25 14:21:17 UTC 2013

I'm not sure creating a brand new extension (ckanext2) is the right
way to go, for me it feels more complicated having to maintain twice
as much repos just for the convenience of having a new namespace. For
users installing an extension choosing ckanext/ckanext2 is at least as
annoying (I would say a bit more) than pointing to a particular branch
or tag, and for us it means that we can maintain a single repo.

I don't think we need to create a new branch for each CKAN core
release if there haven't been any changes needed on the extension.
Perhaps the easiest way is to go is using tags that match ckan core
release, so eg in the release-2.0 branch there could be ckan-2.0,
ckan-2.1 tags, even pointing to the same commit if the extension is
indeed compatible between them. The problem with tags is what happens
if the extension gets updated with new features (still compatible),
you still want users to get the latest code, but that would mean
moving the tag which I'm not sure if it a good idea.

Whether if on the master/release-v.2.0 branch we keep compatibility
for stuff like the genshi templates is a different matter. I'm also +1
on clean start, but this may need to be reviewed for particular cases.

I agree it would be good to get feedback from users using extensions
on their instances.

Adrià

On 25 January 2013 12:21, Toby Dacre <toby.okfn at gmail.com> wrote:
> Revisiting this issue - now that I am going to be updating the archiver and
> qa extensions for 2.0 and I am keen to clean them up to be example
> extensions if possible.
>
> For this I want to break the 1.x compatibility and make a clean start for
> 2.x eg remove all IGenshiFilters etc use the plugins.toolkit try to not
> reach into ckan
>
> so the options I see are
>
> a) branch release-v2.x (or whatever) this feels a bit complicated and hacky
> but is the easiest in the short term but OI think has long term costs.
>
> b) create a new extension ckanext2-qa, ckanext2-archiver so we get a whole
> new namespace.  We could make ckan 2.0 accept both namespaces and it would
> maybe make things less confused for ckan 1.x
>
> c) some other solution I don't know yet
>
> Personally I think ckanext2 is my preferred option but we need a definite
> decision that we are happy with and can communicate to our users
>
> I'm keen for feedback on this idea from ckan devs and the wider ckan
> community dread, ross etc
>
> Toby
>
>
>
>
>
> On 18 January 2013 15:36, Toby Dacre <toby.okfn at gmail.com> wrote:
>>
>>
>>
>> On 18 January 2013 09:30, Ross Jones <ross at servercode.co.uk> wrote:
>>>
>>> Toby,
>>>
>>> Do you have any suggestions on the best way to keep the extensions
>>> working with 1.x, and do you have objections to branching the current code
>>> into a 1.x branch?  There are still a lot of sites on 1.x for whom the
>>> upgrade to 2.0 would be very difficult, or at least very time consuming, at
>>> least in terms of templating - maybe not immediately, but at some point in
>>> the future.
>>>
>>
>> Ross,
>>
>> Hi, I agree it is important to keep 1.x extensions running.  We should at
>> the minimum branch at a working version.
>>
>> Personally I'm very much in to maintaining backwards compatibility where
>> we can.  Some extensions can support both ckan 1.0 and 2.0 together easily.
>> But for others it is more difficult.
>>
>> But we should keep the existing stuff working.
>>
>> I'd really like us to get some good extension writing docs at some point
>> but it would require quite a bit of work and some decisions being made.
>>
>> basically 1.x we need to use genshi templates, 2.0 we can use both but
>> genshi is due to die at some point so they should use jinja2 so to support
>> both we need both template types.  With this we could postpone killing
>> genshi and just keep genshi templates (this may be the best approach)
>> switching to template helpers so the extension adds a helper function that
>> renders a snippet means we don't need IGenshiStreamFilter which is the main
>> problem.
>>
>> There are more issues with including stuff from ckan outside of
>> ckan.plugins that cause problems.  I think we need to look at each extension
>> individually.
>>
>> Hope that helps.  let me know if you need any specific info.  Hope all is
>> good with you.  I'm in a bar on a beach in Thailand so can't complain too
>> much
>>
>> Toby
>>
>>> Ross
>>>
>>> On 18 Jan 2013, at 04:36, Toby Dacre wrote:
>>>
>>> My thoughts on this is that it would be nice to have extensions that just
>>> work and do not need to be updated just because ckan has changed.
>>>
>>> Once an extension is ckan 2.0 compatible (and correctly written) then it
>>> should work for all future versions of ckan. Therefore there would be no
>>> need to release a 2.0, 2.1, 2.x of the extension.  This is mainly about
>>> using plugins.toolkit as the only method of integration with ckan.  Now that
>>> we can call get_action() without a context the last main hurdle has been
>>> removed as extensions needed to import ckan.model before this.
>>>
>>> 2.0 also moves to Jinja2 so it is a good cut off point or else we need
>>> multiple templates or keep genshi ones (but it would be nice to remove these
>>> in 2.1 or 2.2)
>>>
>>> Hmm
>>>
>>> This is all a bit messy.  My main desire with extensions is to isolate
>>> them from core as much as possible to allow refactoring without breakage.
>>>
>>> As a reminder if we need new things added to the toolkit then this is
>>> possible if they make sense and we are happy to support them long term.  But
>>> much of the issue feels is about how extensions are written so for exam[le I
>>> don't think they should ever include lib.helpers but the can access any
>>> helper functions within their templates for example - again this gives us
>>> flexibility that we need to maintain the code and give power to the end
>>> user.
>>>
>>> It would be nice to have better extension writing guidelines at some
>>> point.
>>>
>>> tobes
>>>
>>>
>>> On 17 January 2013 11:29, Sean Hammond <sean.hammond at okfn.org> wrote:
>>>>
>>>> I agree. I think to keep it simple and consistent our recommendation
>>>> should just be that extension branches track the CKAN master and release
>>>> branches, even though in reality, very new or simple extensions will
>>>> probably only have the one master branch (but by the time they have
>>>> conditional behaviour like googleanalytics does, we should just
>>>> recommend them to use the branches).
>>>>
>>>> We'll have to change the install instructions in the README file of each
>>>> extension, and probably mention it for extension authors in the 'writing
>>>> extensions' sphinx docs too.
>>>>
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