[Qgis-developer] Processing algorithms and API breaks

Alexander Bruy alexander.bruy at gmail.com
Mon Mar 7 00:13:09 PST 2016

Hi all,

Processing, became an important part of QGIS. More and more users use it
and rely on it, especially when they developed their own models and scripts.
So we should keep Processing algorithms as stable as possible and don't
change their descriptions.

On other hand there are many bugreports and feature requests which require
changing algorithms description to be fixed/impelemented. This can be considired
as "API" break, as scripts and models which use affected algorithms
and were developed before such changes will not work. For example,
there were many
PR about fixing GRASS and SAGA algs, which change their descriptions. Time
from time we also fix bugs in native QGIS algs and also need to change
algorithm description, e.g. by replacing one parameter type with another or
adding new parameter.

I see only two solutions:
1. Postpone such changes for next major QGIS release when API break is
allowed. In this case all existing scripts/models will work. But we
should live
with bugs and without some features, even if fix already available and keep the
code of this fixes in sync with master until next major release.
2. Allow "API" breaks in Processing. In this case we create additional pressure
on the authors of 3rd party models/scripts and force them to follow Processing
changes and update their code accordingly.

What do you think, which approach we should choose?

Alexander Bruy

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