Change data source of an attribute table frame with data-defined override button

[GeoGyro]

Context

Switch data source of an attribute table frame in a composer with data-defined override button to take into account if a layer's name changed.

Description

In a composer build with an attribute table frame, data-defined override button don't apply when trying to change the data source.

As documentation specify, data-defined override button allows to dynamically change the layer which is used to populate the table, but changes are not applied.

The source layer reference in the main drop-down list stays persistent, even if @layer_name or @layer_id are changed in expression builder. Same behaviour observed with Geopackages and Shapefiles.

Expressions tryed to define an other source layer (e.g myLayer_1 and myLayer_2) :
'myLayer_2'
@layer_name = 'myLayer_2'

Expressions tryed to switch between two layers (e.g myLayer_1 and myLayer_2) :
@layer_name = coalesce('myLayer_1','myLayer_2')
coalesce(layer_property('myLayer_1','name'),layer_property('myLayer_2','name'))

If it's not a bug, may documentation needs to be more explicit and provides a syntax example ?

How to reproduce

• Create a project with 2 data sources
• Create a composer
• Add an attribute table frame
• Switch data source to an other layer with data-defined override button

QGIS and OS versions

3.10.2-A Coruña
Windows 10 Professional

Additional context
Documentation : https://docs.qgis.org/3.10/en/docs/user_manual/print_composer/composer_items/composer_attribute_table.html#main-properties

Source issue : https://gis.stackexchange.com/questions/360482/qfield-display-attributes-table-frame-in-pdf-with-editing-offline-mode

[DelazJ]

Hi @GeoGyro
I did not try to replicate but as far as you are referring to the docs, I see it mentions that the layers should have the same (displayed?) columns. Do you confirm it's your case? The feature implementation PR is at #6530.

[GeoGyro]

Hi,
yes it is. In my case my layers have exactly the same fields. I tried with basics "tests" layers wich only have and id(integer) field and a name(varchar) field.

[nyalldawson]

Your syntax looks wrong. Can you share a project which demonstrates this for me to investigate?

[GeoGyro]

Hi @nyalldawson,

Here is a demo project with 2 layers and a composer :
demo.zip

I have tried differents expressions in data-defined override-button but maybe my syntax is wrong.

In my real case, I want to switch layers's names in a QField project, because QFieldSync rename layers with a (offline) suffix.