[QGIS-Developer] Merge attributes tool and default values

[Nyall Dawson]

On Thu, 12 Dec 2024 at 20:32, Juho Ervasti via QGIS-Developer
<qgis-developer at lists.osgeo.org> wrote:
>
> Hey,
>
> I'm writing about a QGIS issue https://github.com/qgis/QGIS/issues/59494. In summary when using the merge feature tool the attributes for the pending new feature are initially populated with a default value for the field if one is set in the data provider (e.g. Postgres, OGR). The default value set in QGIS doesn't have an effect.
>
> Is this the intended behavior? At least in some cases it would make sense if the value came from the selected features, like it does if a default value is not set.
>
> If it is the intended behavior and shouldn't be changed outright, would it be okay to add an option for it in the Attribute form's "Policies" section, similar to the splitting and duplicating policies?

This was always the intention, so go ahead! Note that there's already
an enum for this at Qgis::FieldDomainMergePolicy. You could follow the
same procedure as is used for Qgis::FieldDomainSplitPolicy to expose
this, auto-populate when reading OGR data sources, and then attach to
QgsField/QgsVectorLayer.

Nyall

>
> Best regards,
> Juho Ervasti
> GIS Specialist
> Gispo Finland Ltd.
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