Combo box in database mode: datasource/item selection not persisted, check only warns, and the written widget fails mxbuild CE0463 #1583

Summary

A Combo box in database mode can't be written. check only warns (MDL-WIDGET06) and passes, exec writes the widget, and mxbuild then fails with CE0463, so the result doesn't build.

Repro

mdl 1;
create or modify microflow Mod.GET_Parents () returns List of Mod.Parent as $List
begin
  retrieve $List from Mod.Parent;
  return $List;
end;
create or modify page Mod.Child_Edit (
  Title: 'Child edit',
  Layout: Atlas_Core.Atlas_Default,
  Params: ( $Child: Mod.Child )
) {
  dataview dvChild (DataSource: $Child) {
    combobox cbCode (source: 'database', optionsSourceDatabaseDataSource: microflow Mod.GET_Parents, optionsSourceDatabaseItemSelection: 'Single', optionsSourceDatabaseCaptionAttribute: Name, optionsSourceDatabaseValueAttribute: Name, databaseAttributeString: Code)
  }
};

• check reports 3 issues: 0 errors, 3 warnings, including:

  widget `cbCode` (combobox) property `optionsSourceDatabaseDataSource` is recognized but not yet persisted by mxcli — a non-default value will be dropped; set it in Studio Pro if needed [MDL-WIDGET06]
  widget `cbCode` (combobox) property `optionsSourceDatabaseItemSelection` is recognized but not yet persisted by mxcli … [MDL-WIDGET06]
  Check passed!
  

• exec reports Created page Mod.Child_Edit.
• mx check reports [CE0463] "The definition of this widget has changed. Update this widget …" at Combo box 'cbCode'.

Expected

The data source and item selection are written; the widget's own definition declares them (Combobox 2.6.2). Until they are, check should fail rather than warn, because the page it lets through doesn't build.

Workaround

Use a list view with a row action as a pick list, or a combo box in context or association mode.

Tested with: mxcli nightly-20261018-80b1b8d0d (also seen on v0.26.0), Mendix 11.12.5, macOS arm64.