Copy/paste style category "Form" is missing some settings

[pathmapper]

What is the bug or the crash?

Copy/paste style category Form is missing some settings, e.g. the Default value for Text Edit Widget type.

Steps to reproduce the issue

1. Open test_project_and_data.zip
2. Check the Form settings for layer testdata with form in layer properties: The field GN has a Default value
3. Copy the Form settings from layer testdata with form using the layer contextmenu: Styles -> Copy Style -> Form
4. Paste the Form settings to layer testdata using the layer contextmenu: Style -> Paste Style -> Form
5. Check the Form settings for layer testdata in layer properties: The Default value for field GN is missing.

Versions

QGIS version	3.21.0-Master	QGIS code revision	08d8ccb
Qt version	5.12.8
Python version	3.8.10
GDAL/OGR version	3.0.4
PROJ version	6.3.1
EPSG Registry database version	v9.8.6 (2020-01-22)
Compiled against GEOS	3.8.0-CAPI-1.13.1	Running against GEOS	3.8.0-CAPI-1.13.1
SQLite version	3.31.1
PostgreSQL client version	12.8 (Ubuntu 12.8-0ubuntu0.20.04.1)
SpatiaLite version	4.3.0a
QWT version	6.1.4
QScintilla2 version	2.11.2
OS version	Ubuntu 20.04.3 LTS
Active Python plugins	sagaprovidergrassproviderMetaSearchprocessingdb_manager

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

Some other form settings are also missing, e.g. the Constraints.

[elpaso]

The source of the issue is that the information about default values is stored in the "Fields" category even if in the properties dialog it is editable in the "Forms" tab, I'll check how this can be fixed but I'm afraid it could potentially break existing code (e.g. from plugins).

@3nids / @m-kuhn any though on this topic?

[3nids]

The categories of the copy/paste do not exactly match the tab I guess.

It might make sense to group the two categories into a single one?

[elpaso]

The categories of the copy/paste do not exactly match the tab I guess.

It might make sense to group the two categories into a single one?

Probably a good idea. From a user perspective i think it is expected that the categories match the tabs (same name, same icon etc.).

There isn't much information stored in the "Fields" tab right now, it's just the flags IIRC.

[3nids]

yes, exactly.
I think Fields category is constraints + defaults + alias + flags.

I have no strong opinion.
The current approach is the most logic from a semantic point of view, but might not be very intuitive.

I think this can be reduce to the question: would there be a case where it makes sense to copy only fields or only forms.

[pathmapper]

@elpaso @3nids thanks for looking into this and the workaround (= copy/paste All Style Categories).

i think it is expected that the categories match the tabs (same name, same icon etc.).

Would be great, here's an attempt to map the current situation (not entirely sure about everything, also might be that Custom Properties, Geometry Options and Relations are also having an equivalent):

[bastooo]

I just had the experience to break my project, due to the confusing bug, that the constraint & default values are not stored in the Forms subcategory. So I copied half of the information and later on, the data, which was collected in the field was complete rubbish..

I would appreciate a lot, if I copy the Forms-style information from one layer to another, that everything I configured is copied.

[pathmapper]

Note:
Layer Variables is in Custom Properties