[QGIS-Developer] Can't find SAGA devel versions after r413c6e5

[Rainer Hurling]

Hi Alex,

Thanks for the quick and detailed answer.

Am 08.06.2017 um 11:29 schrieb Alexander Bruy:
> Hi Rainer,
> 
> 2017-06-08 10:24 GMT+03:00 Rainer Hurling <rhurlin at gwdg.de>:
>> For some reasons, we don't package our system with different versions of
>> SAGA GIS. Recent FreeBSD comes with SAGA GIS version 3.0.0, I am working on
>> an update to version 4.1.0.
>>
>> With your latest updates to QGIS (r413c6e5), newer versions of SAGA GIS than
>> 2.3.x are not recognized any more :(
>>
>> I am familiar with the background, that QGIS processing only garantees to
>> work well with the SAGA GIS LTR version. But there was a kind of tacit
>> agreement for several years now, that QGIS processing tools also accepted to
>> display (and somewhat work with) newer SAGA GIS versions.
> 
> Previously QGIS Processing supported multiple SAGA versions, but as SAGA
> devs often changed API even between minor versions it was a real pain to
> maintain compatibility and provide users with robust and working SAGA inteface.
> Because for each change in SAGA API we need not only update algorithms
> descriptions but also add some workaronds in the Processing source code.
> 
> After release of SAGA LTR we had several long discussions and finally decided
> that better to have good support for single SAGA version that multiple partially
> broken version. That's why support for all other versions was removed. We also
> removed option to choose another SAGA installation, as this makes no sense
> now and can lead to confusion in case when user select unsupported SAGA
> version.
> 

In principle I understand this point of view, but it makes it relatively 
difficult to identify the necessary changes for newer SAGA GIS versions.

And as I outlined before, there are constraints on some OS for the 
presence of newer SAGA GIS versions. In the past, the QGIS user was able 
to use most of the SAGA GIS functions, as only some of the functions had 
bigger API changes.

>> Now my request: It would be fine and at least important for FreeBSD users,
>> to have the possibility to use SAGA GIS > 2.3.x with QGIS 2.18.9 again.
> 
> I'm afrad this is not possible, as we have no resources to keep algorithms
> descriptions and, more importantly, source code updated with numerous SAGA
> API breaks in every SAGA release.
> 
> As an option I can suggest to create altenate SAGA provider plugin which will
> support non-LTR SAGA versions.
> 
> 

This would be a very nice option to have such an additional support. A 
provider plugin for (newer) non-LTR SAGA versions could throw a 
warnings, that this SAGA GIS version is not fully supported and the user 
has to expect problems ...