[stagknee]

Closes #1632.

What it fixes

Every Marketplace Calendar written by mxcli failed a plain mx check with CE0463 "The definition of this widget has changed". mxcli docker check hid it, because it runs update-widgets on a temporary copy first.

The Calendar has no embedded template, so its Type is generated from the .mpk. Its toolbarItems object list declares its sub-properties directly under <properties>, each with a <category> element. modelsdk/widgets/mpk read only <properties><propertyGroup>, so toolbarItems had no Children and was stored with ValueType.ObjectType: null.

How

• xmlProperty gains NestedDirectProps (properties>property) and Category.
• nestedGroups returns the declared groups plus one caption-less group holding the direct sub-properties. Both call sites (top-level and nested object properties) use it.
• collectNestedProperties gives a sub-property outside any group its own <category>. Grouped sub-properties keep their caption chain, unchanged.

sdk/widgets/mpk (used by widget init, the catalog and the widget docs) already reads both shapes. This brings the template-side parser in line with it, using the same field name and order.

Also included: CHANGELOG (Fixed), a finding in findings/modelsdk/, and mdl-examples/bug-tests/1632-calendar-toolbaritems-definition.mdl.

Evidence

• Tests:

  • modelsdk/widgets/mpk/objectdirect_test.go covers parsing: direct sub-properties in document order with their own category and attributes, and a grouped control that keeps its group caption.
  • modelsdk/widgets/objectdirect_test.go covers the path end to end, from a zipped .mpk through ParseMPK to GenerateFromMPK: the object property gets a WidgetObjectType with both sub-property types, and itemType gets the category Appearance.
  • Both fail on main and pass with the fix.

• Real run (Mendix 11.12.5 scratch app, Calendar 2.6.1), plain mx check after exec. "main" here is the 2026-10-20 nightly (3b24e5a), whose modelsdk/widgets is identical to current main:

  Script	main	this branch
  bug-tests/1632-calendar-toolbaritems-definition.mdl	1 × CE0463	0 errors
  bug-tests/1578-calendar-expression-properties.mdl	2 × CE0463	0 errors

  • The stored Calendar pages are identical (ids stripped) to a copy that mx update-widgets rewrote.
  • Control: doctype-tests/32-pluggable-widget-object-lists-v010.mdl covers Accordion, PopupMenu, Maps static and dynamic, area and line chart, and heat map. All 9 pages are stored identically by main and by this branch, ids stripped. One line-chart value (smooth) had to change to spline, because the app's Charts version doesn't accept it.
  • That fixture's Maps map2 reports CE0463 on both main and this branch, so it's unrelated and left alone.

• Windows: go test ./modelsdk/... passes. ./mdl/executor/, ./mdl/catalog/ and ./cmd/mxcli/ show the same failures as unchanged main on Windows: 28 executor tests (layout, describe, OData file paths, type checking) and TestSaveToFile_ConcurrentWritersAndReaders. go vet and gofmt are clean.

• Linux (golang:1.26.6-bookworm, ANTLR 4.13.2): make grammar build test check-mdl check-findings check-conformance check-migration-reference lint-go all pass.

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