[ako]

Fixes mendixlabs#1461 (rows; columns have no visibility in Mendix — see below).

Problem

• Rows: a row is built outside buildWidgetV3, pages.LayoutGridRow had no field, describe never read the setting, and the writer always wrote null. So row (Visible: …) passed check and exec and was not written.
• Data loss (measured): on a pedapp copy with three conditional rows, describe → exec with the old binary reported "Replaced page" and all three row conditions were gone. ALTER does not lose it (it edits stored BSON). TestApp's only conditional row sits inside a pass-through timeline slot, which is why the roundtrip harness never caught this.
• Columns: none of the 732 Studio Pro layout-grid columns in TestApp + PedApp carries visibility, while all 483 rows carry the setting; the vendored gen LayoutGridColumn has no such property. So column visibility is not a thing to write.

Fix

• LayoutGridRow.ConditionalVisibility (sdk/pages).
• Builder: pb.childVisibility (expression and Attr in (…) forms), now shared by buildTabPageV3 (Tab page CaptionParams and Visible: pass check and exec, then are silently not written mendixlabs/mxcli#1465) and the row builder. A top-level row keeps the condition on its wrapping container only.
• Writer: layoutGridRowToGen writes the setting instead of null.
• Describe: parseLayoutGridRows reuses extractConditionalSettings.
• Check: validate_layoutgrid_column_visible.go warns MDL-WIDGET07 for Visible: on a column inside a row and points at the row or a container. The file is added to TestWidgetRuleIDsAreNotReused's list of MDL-WIDGET07 raisers.
• Skill note in create-page/reference/widgets.md (example written as a full create page so the conformance gate parses it).

Tests

• TestLayoutGridRow_VisibleIsWritten, TestLayoutGridRow_TopLevelRowVisibleOnContainerOnly, TestDescribe_LayoutGridRowVisible, TestCheck_LayoutGridColumnVisibleDropped
• backend: TestLayoutGridRow_WritesConditionalVisibility

Proof by revert: each fails with its fix stubbed.

Real tools: the TestApp snippet now describes with its Visible: and re-executes as "Unchanged"; with the fix the pedapp describe → exec reports "Unchanged" instead of wiping rows. mx check on a pedapp copy with all three row forms: same error count as the same page without visibility (no new errors).

Validation

• go test mdl/backend/modelsdk, mdl/executor, sdk/pages, mdl/conformance; roundtrip TestTestAppRoundTrip + TestPedAppRoundTrip pass, no allowlist change; go vet, gofmt, make check-findings clean
• Not validated in Studio Pro.

Noticed, not changed

MDL-WIDGET43 ("datagrid column … $currentObject", an error) also fires on a layout-grid column with Visible: $currentObject/… — a misleading label, out of scope here.

🤖 Generated with Claude Code

https://claude.ai/code/session_01VKmbj53BC2vuUWYmgWgfQ5

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