[ako]

Refs #1326 (mirror of mendixlabs#1453). This is the prerequisite step of the proposal in #1564.

Symptom

An Accordion group has two widget slots, headerContent and content. Describe printed both as the group's body, so regenerating the page from the description moved the header widget into the body. Measured on a fresh blank Mendix 11.13.0 app:

stored:       headerContent -> [txtHead], content -> [txtBody]
regenerated:  content -> [txtHead, txtBody]

The block form that keeps them apart couldn't run either:

✗ page H.P: `headercontent` is not a widget in this project [MDL-WIDGET25]

The builder does accept that block (its item-slot pass routes it). The checker, though, resolved no parent definition for a child of an object-list item, so the item's own slot keyword fell through to "not a widget".

Updating the existing page from the description reports Unchanged page and hides the loss. Only a run against a fresh app shows it, and that is the case that matters: regenerating a page from describe output.

Fix

• Describe: extractObjectListItem keeps each widget slot apart. The body slot prints as the item's children; every other non-empty slot prints as a <keyword> { … } block, reusing outputChildSlots.
• One body rule: "content, else the first widget slot" is now bodyItemSlotKey, called by both CREATE's defaultItemSlotKey and describe, so the two can't disagree.
• Check: validateWidgetTreeIn passes an item's mapping to its children. A slot the item declares is accepted; a misspelt one is still refused.

Describe now prints:

group (headerRenderMode: 'custom', …) {
  headercontent {
    dynamictext txtHead (Content: 'Header')
  }
  dynamictext txtBody (Content: 'Body')
}

Evidence

• Control: before the fix, the new tests fail with the body holding both widgets, with no headercontent block, and with MDL-WIDGET25 at check. The misspelt-block test passes before and after, so the check wasn't simply switched off. The accept test fails on any error-severity violation, not just rule 25/26.
• Real run (fixed build): describe the page, then exec the description on a fresh app. check passes, the result is headerContent -> ['txtHead'], content -> ['txtBody'], and mx check reports The app contains: 0 errors.
• Regression script: mdl-examples/bug-tests/1453-describe-accordion-headercontent-slot.mdl. Finding recorded.
• make build && make test && make lint, make check-mdl and make check-findings all pass.

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