[QGIS-Developer] Migrating plugins

[Richard Duivenvoorde]

Hi Javier,

The wiki is 'just' a github wiki. Can you try to edit it with your
github credentials? Or create a github account for it?

If that fails, I'll try to copy your info in it.

Regards,

Richard Duivenvoorde


On 11-01-18 09:44, Javier Becerra Elcinto wrote:
> Hi Paolo,
> 
> Thanks for the effort of setting up the wiki page, we have started
> migrating some plugins and missed some kind of "standard"
> guidelines/best practices.
> 
>  I was not able to find a way to contribute to the wiki, and could not
> find an issue/forum associated with it - I do not know much about QGis'
> team development workflow, so that there may be resources I am not aware
> of (in that case, it might be a good idea to link them from the wiki?).
> 
> So I guess this list is the way to go at the moment, I will share my two
> cents based on our experience migrating to QGis3 (we have recently made
> a pull request to complete the migration of profiletool plugin to QGis3
> https://github.com/PANOimagen/profiletool/commit/2631bc4600938d7beeaf6281bcb8de16a6de912c
> and are working on other internal plugins):
> 
> -We iniatially thought on creating a compatibility layer to allow Qgis2
> plugins to run (mostly?) unmodified on QGis3; however that seems like a
> bad idea in the long term, and followed the monkey-patching strategy set
> forth by opengis.ch in their qgis2compat plugin
> (https://github.com/opengisch/qgis2compat). This means, we make all the
> code qgis3 compatible, and patch QGis2 on runtime to provide Qgis3 api
> compatibility. In the long term, dropping support for QGis2 should be as
> simple as removing the apicompat module, the plugin's code would remain
> unmodified to keep on running on QGis3.
> 
> -Unfortunately qgis2compat has not been updated in the last 10 months,
> and we do not want to add an additional dependency to the plugins, so
> that we have included their apicompat files as needed and completed the
> missing bits we found (e.g. QgsPointXY). We can contribute our additions
> to Qgis2compat if someone is interested.
> 
> -There are however some modifications that we have not been able to
> manage with monkeypatching, for instance
> PyQt4.QFileDialog.getOpenFilenames returns a list of files and
> PyQt5.QFileDialog.getOpenFilenames returns a tuple with the list of
> files and the extensions (i.e. PyQt5.QFileDialog.getOpenFilenames ==
> PyQt4.QFileDialog.getOpenFilenamesAndFilter); modifying PyQt4's
> behaviour can lead to other plugins, who expect the proper PyQt4 api, to
> stop working. We prefer not to introduce 'new' functions (i.e.
> PyQtx.QFileDialog.getOpenFilenames5) that would not be neither PyQt4 nor
> PyQt5, and the best option we have found is to check PyQt version or use
> a try/except to manage compatibility. We do not like it, but it is the
> least ugly solution we could find. If someone has a nicer/more
> elegant/more pythonic solution we are willing to hear from you :)
> 
> Regards,
> 
> Javier
> 
> 
> 
> El 09/01/2018 a las 11:17, Paolo Cavallini escribió:
>> Il 09/01/2018 11:13, Werner Macho ha scritto:
>>> Hi Paolo,
>>> Good initiative!
>>> I will contribute if I find anything important to say. ;)
>> Thank you Werner. Any help will be useful, both in writing the guide and
>> in testing and streamlining it.
>> All the best.
> 
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