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

[Toby Dacre]

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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