fix: silent-property-drop cluster — container RenderMode, Calendar expressions, column Filterable

.claude/skills/fix-issue/findings/mdl-executor/2026-10-20-column-filterable-names-the-filter-slot.json

@@ -0,0 +1 @@
+{"area":"mdl/executor","date":"2026-10-20","symptom":"`column (Attribute: Name, Filterable: true)` on a Data grid 2: the original report was a silent drop; on current main check refuses it, but with a project the message lists the column's properties without the `filter` slot, and without one it suggests `did you mean FilterType?` — a key the column does not have","cause":"The refusal (MDL-WIDGET01 / MDL-WIDGET07) built its hint from property names only: the item's widgets slots (`content`, `filter`) are not properties, so neither the property list nor nearestKey over the builtin union could name the slot the author was reaching for","file":"`mdl/executor/validate_widgets.go` (`widgetSlotHint`), `mdl/executor/validate_widget_embedded_schema.go` (`widgetSlots`)","insight":"Re-run an old silent-drop report on main before fixing it: #177 had already become a refusal, and what was left was the message. A did-you-mean over property names cannot reach a slot, so a key whose prefix is a slot key (`Filterable` → `filter`) needs its own answer naming the body form and the widget types the slot routes (itemSlotAcceptedChildTypes, already per widget). Measured on Mendix 11.13.0: the suggested `column (Attribute: X) { textfilter tf }` builds 0 errors. Control: both new assertions fail on main with `its properties are attribute, header (Caption)` and `did you mean FilterType`","refs":["mendixlabs/mxcli#177","#1230"]}

.claude/skills/fix-issue/findings/mdl-executor/2026-10-20-container-rendermode-reads-as-dropped.json

@@ -0,0 +1 @@
+{"area":"mdl/executor","date":"2026-10-20","symptom":"`container ctnMain (RenderMode: 'Main')` in `create or modify layout` passes check and exec, then `describe layout` prints `container ctnMain (Class: 'app-main')` — reported as \"the value isn't stored\"; `alter layout … set (RenderMode: …)` refused with `property \"RenderMode\" is not a property of this built-in widget`","cause":"The write was fine: `bson dump` showed `RenderMode: \"Main\"` on the stored Forms$DivContainer. DESCRIBE's DivContainer branch never read RenderMode (only DynamicText did), the ALTER `rendermode` case routed only dynamic texts and sent containers to the pluggable setter, and buildContainerV3 cast any string straight to the enum, so `'main'` or `'Banner'` was stored verbatim","file":"`mdl/executor/cmd_pages_describe_parse.go`, `cmd_pages_describe_output.go`, `cmd_pages_builder_v3_layout.go` (`buildContainerV3`), `mdl/backend/pagemutator/mutator.go` (`setContainerRenderModeMut`), `sdk/pages/pages_widgets_container.go` (`CanonicalContainerRenderMode`)","insight":"A report that a value \"isn't stored\" is usually read off `describe`; run `bson dump` before touching the write path — here it split a suspected write drop into a read-side gap in one command, and the builder had been right all along. The sdk enum had drifted too (`Div`, `Form`; Mendix's set is Div…Address in modelsdk/gen/pages), so take the member list from the generated enum rather than the hand-written one. Control: the four new tests fail on main with `describe dropped the container's RenderMode`, `RenderMode = \"main\", want Main`, `'Banner' must be refused` and `property \"RenderMode\" not found on this widget`","refs":["mendixlabs/mxcli#1582","#1487"]}

.claude/skills/fix-issue/findings/mdl-executor/2026-10-20-pluggable-top-level-expression-unmapped.json

@@ -0,0 +1 @@
+{"area":"mdl/executor","date":"2026-10-20","symptom":"Marketplace Calendar 2.6.1 page passes check and exec, then `mx check` fails `[CE0642] \"Property 'Editable' is required.\"` and `\"Property 'Show event date range' is required.\"`; `editable: 'true'` is accepted with no warning and changes nothing, `showEventDate:` warns MDL-WIDGET06 \"will be dropped\" although it is written, and `describe page` prints neither","cause":"Four hops, each dropping the same value: (1) GenerateFromMPK's createDefaultWidgetValue had no Expression case, so `defaultValue=\"true\"` was written as an empty expression; (2) GenerateDefJSON emitted no mapping for a top-level `expression` property, leaving it in KnownProperties (MDL-WIDGET06) and written only by the explicit pass; (3) that pass skips builtin names, and `editable` is also the widget-level editability, which the Calendar's package does not declare — so the widget's own `editable` was unreachable in every spelling; (4) extractExplicitProperties had no Expression branch","file":"`modelsdk/widgets/augment.go` (`createDefaultWidgetValue`), `mdl/executor/widget_defs.go` (`GenerateDefJSON`, generator v19), `mdl/executor/widget_engine.go` (`resolveMapping`, `applyOperation`), `mdl/executor/pluggable_system_props.go` (`editableIsOwnProperty`), `mdl/executor/cmd_pages_describe_pluggable.go`","insight":"A builtin MDL key and a widget's own property of the same name collide silently: the builtin always wins, and when the widget does not declare the matching system property the builtin is a no-op too. Decide the routing in the def generator, which reads the .mpk's system properties, so check and build read one answer. The cheapest probe was the reporter's table — `showEventDate:` made the CE0642 go away while `editable:` did not, which already says the explicit pass writes expressions and something else eats `editable`. Make the template write declared defaults first: that alone makes every Calendar page build, before any MDL names the property. Measured on Mendix 11.13.0 with Calendar 245304 v2.6.1: main → 2× CE0642; this branch → 0 errors with neither, both 'true' and both false/'false', and describe → exec reports Unchanged","refs":["mendixlabs/mxcli#1578","#1483"]}

docs-wiki/bug-patterns/silent-property-drop.md

@@ -146,6 +146,22 @@ model holding a value that the tool reports as absent — the same lossy round t
 wearing the right answer. Several findings here are the follow-up half of a fix
 that shipped write-only.
 
+**"Not stored" is usually read off `describe` — check the store first.** A
+report that a value was dropped is almost always an inference from `describe`
+printing nothing, and `describe` is a separate hop that can be the only one
+missing. A container's `RenderMode` was on disk all along; only the read side
+had never learnt it. One `bson dump` splits a write drop from a read gap before
+any code is opened, and points the fix at the right half.
+
+**A builtin key can shadow a widget's own property of the same name.** The
+universal names (`Editable`, `Visible`, …) win over a pluggable widget's own
+key, and where the package declares no matching system property the builtin is
+a no-op as well — so the widget's own property is unreachable in every
+spelling, with nothing to warn about because the key is "known". Which meaning
+a key has is a fact of the package (its system properties), so decide it where
+the package is read — the definition generator — and let check and build both
+read that one answer.
+
 **A half-wired feature is worse than a missing one.** When the grammar already
 accepts a form, scripts using it look correct and produce models without it.
 Before assuming a spelling works, follow the whole chain: AST → model → both

mdl-examples/bug-tests/1578-calendar-expression-properties.mdl

@@ -0,0 +1,52 @@
+-- mendixlabs/mxcli#1578: a page with the Marketplace Calendar (content 245304)
+-- passed `check` and `exec`, then `mx check` failed with
+--   [CE0642] "Property 'Editable' is required." at Calendar 'CalRepro_Calendar'
+--   [CE0642] "Property 'Show event date range' is required."
+-- Both are `type="expression" defaultValue="true"` in Calendar.xml. The
+-- template wrote them empty, `editable:` only ever reached the widget-level
+-- editability (which the Calendar does not declare), `showEventDate:` drew a
+-- false MDL-WIDGET06, and `describe page` printed neither.
+-- After the fix an unnamed one gets its declared default, `editable:` and
+-- `showEventDate:` are written in every spelling, and describe prints both.
+-- Needs: `mxcli marketplace install 245304 -p <app>` first.
+mdl 1;
+
+create module BugTest1578;
+
+create persistent entity BugTest1578.LeaveRequest (
+  Reason: String(200),
+  StartDate: DateTime,
+  EndDate: DateTime
+);
+
+-- Neither property named: both get their default, `mx check` is clean.
+create or modify page BugTest1578.CalDefaults (Title: 'Calendar', Layout: Atlas_Core.Atlas_Default) {
+  pluggablewidget 'com.mendix.widget.web.calendar.Calendar' calDefaults (
+    databaseDataSource: database BugTest1578.LeaveRequest,
+    titleType: 'attribute',
+    titleAttribute: Reason,
+    startAttribute: StartDate,
+    endAttribute: EndDate,
+    view: 'standard',
+    defaultViewStandard: 'month'
+  )
+};
+
+-- Both named with a non-default value.
+create or modify page BugTest1578.CalReadOnly (Title: 'Calendar', Layout: Atlas_Core.Atlas_Default) {
+  pluggablewidget 'com.mendix.widget.web.calendar.Calendar' calReadOnly (
+    databaseDataSource: database BugTest1578.LeaveRequest,
+    titleType: 'attribute',
+    titleAttribute: Reason,
+    startAttribute: StartDate,
+    endAttribute: EndDate,
+    view: 'standard',
+    defaultViewStandard: 'month',
+    editable: false,
+    showEventDate: 'false'
+  )
+};
+
+-- Expect: editable: 'true', showEventDate: 'true' — and 'false' on the second.
+describe page BugTest1578.CalDefaults;
+describe page BugTest1578.CalReadOnly;

mdl-examples/bug-tests/1582-container-rendermode.mdl

@@ -0,0 +1,33 @@
+-- mendixlabs/mxcli#1582: `container ctnMain (RenderMode: 'Main')` in a layout or
+-- page was stored, but `describe` never printed it — so it read as dropped, and
+-- a describe → exec round trip did drop it. `alter layout … set (RenderMode: …)`
+-- was refused with `property "RenderMode" is not a property of this built-in
+-- widget`, and an unknown value (`'Banner'`, or `'main'` as typed) was written
+-- verbatim into the document.
+-- After the fix describe prints `RenderMode: Main`, ALTER sets it, the value is
+-- stored in its canonical spelling, and an unknown member is refused.
+mdl 1;
+
+create module BugTest1582;
+
+create or modify layout BugTest1582.L_Landmarks (
+  layouttype: 'Responsive'
+) {
+  scrollcontainer layoutContainer {
+    region center {
+      container ctnMain (RenderMode: 'Main', Class: 'app-main') {
+        placeholder Main
+      }
+      container ctnNav (RenderMode: nav) {
+        placeholder Nav
+      }
+    }
+  }
+};
+
+alter layout BugTest1582.L_Landmarks {
+  set (RenderMode: 'Header') on ctnNav;
+};
+
+-- Expect: ctnMain (RenderMode: Main, …) and ctnNav (RenderMode: Header).
+describe layout BugTest1582.L_Landmarks;

mdl-examples/bug-tests/177-datagrid-column-filter-slot.mdl

@@ -0,0 +1,27 @@
+-- mendixlabs/mxcli#177: `column (Attribute: Name, Filterable: true)` was
+-- accepted by check and exec and silently dropped — a Data grid 2 column has no
+-- Filterable property. Its filter is the column's `filter` widgets slot.
+-- check now refuses `Filterable:` (MDL-WIDGET01 with -p, MDL-WIDGET07 without)
+-- and the message names the slot and the filter widgets it takes, instead of
+-- listing the column's properties or suggesting `FilterType`.
+-- This script is the form the message points at; it builds with 0 errors.
+mdl 1;
+
+create module BugTest177;
+
+create persistent entity BugTest177.Order (
+  OrderNumber: String(20),
+  Amount: Decimal,
+  PlacedOn: DateTime
+);
+
+create or modify page BugTest177.Order_Overview (Title: 'Orders', Layout: Atlas_Core.Atlas_Default) {
+  datagrid dgOrders (DataSource: database BugTest177.Order) {
+    column (Attribute: OrderNumber) { textfilter tfNumber }
+    column (Attribute: Amount) { numberfilter nfAmount }
+    column (Attribute: PlacedOn) { datefilter dfPlacedOn }
+  }
+};
+
+-- Expect: each column describes back with its filter widget in its braces.
+describe page BugTest177.Order_Overview;

mdl/backend/pagemutator/container_rendermode_test.go

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package pagemutator
+
+import (
+	"testing"
+
+	"go.mongodb.org/mongo-driver/bson"
+
+	"github.com/mendixlabs/mxcli/mdl/backend/bsonnav"
+)
+
+// `alter layout … set (RenderMode: 'Main') on ctnMain` was refused with
+// "property \"RenderMode\" is not a property of this built-in widget", although
+// CREATE writes Forms$DivContainer.RenderMode (mendixlabs/mxcli#1582).
+func TestSetWidgetProperty_ContainerRenderMode(t *testing.T) {
+	for _, tc := range []struct{ in, want string }{{"Main", "Main"}, {"nav", "Nav"}, {"Div", "Div"}} {
+		rawData := makeRawPage(bson.D{
+			{Key: "$Type", Value: "Forms$DivContainer"},
+			{Key: "Name", Value: "ctnMain"},
+			{Key: "RenderMode", Value: "Div"},
+		})
+		m := &Mutator{rawData: rawData, widgetFinder: findBsonWidget}
+		if err := m.SetWidgetProperty("ctnMain", "RenderMode", tc.in); err != nil {
+			t.Fatalf("SetWidgetProperty(RenderMode=%s): %v", tc.in, err)
+		}
+		if got := bsonnav.DGetString(findBsonWidget(rawData, "ctnMain").widget, "RenderMode"); got != tc.want {
+			t.Errorf("RenderMode = %q, want %q", got, tc.want)
+		}
+	}
+}
+
+func TestSetWidgetProperty_ContainerRenderModeInvalid(t *testing.T) {
+	rawData := makeRawPage(bson.D{
+		{Key: "$Type", Value: "Forms$DivContainer"},
+		{Key: "Name", Value: "ctnMain"},
+		{Key: "RenderMode", Value: "Main"},
+	})
+	m := &Mutator{rawData: rawData, widgetFinder: findBsonWidget}
+	if err := m.SetWidgetProperty("ctnMain", "RenderMode", "H1"); err == nil {
+		t.Fatal("RenderMode H1 on a container must be refused")
+	}
+	if got := bsonnav.DGetString(findBsonWidget(rawData, "ctnMain").widget, "RenderMode"); got != "Main" {
+		t.Errorf("a refused value changed the stored RenderMode to %q", got)
+	}
+}

mdl/backend/pagemutator/mutator.go

@@ -3264,6 +3264,9 @@ func setRawWidgetPropertyMut(widget bson.D, propName string, value any) error {
 		if isDynamicTextWidget(widget) {
 			return setDynamicTextRenderModeMut(widget, value)
 		}
+		if typ := bsonnav.DGetString(widget, "$Type"); typ == "Forms$DivContainer" || typ == "Pages$DivContainer" {
+			return setContainerRenderModeMut(widget, value)
+		}
 		return setPluggableWidgetPropertyMut(widget, propName, value)
 	default:
 		// Try as pluggable widget property
@@ -3320,6 +3323,27 @@ func setDynamicTextRenderModeMut(widget bson.D, value any) error {
 		fmt.Sprint(value), bsonnav.DGetString(widget, "Name"), strings.Join(names, ", "))
 }
 
+// setContainerRenderModeMut writes a container's RenderMode — the HTML element
+// it renders as — in place, canonically spelled; an unknown member is refused
+// before the document is touched (mendixlabs/mxcli#1582).
+func setContainerRenderModeMut(widget bson.D, value any) error {
+	s, _ := value.(string)
+	mode, ok := pages.CanonicalContainerRenderMode(s)
+	if !ok {
+		names := make([]string, len(pages.ContainerRenderModes))
+		for i, m := range pages.ContainerRenderModes {
+			names[i] = string(m)
+		}
+		return fmt.Errorf("invalid RenderMode %q for container %q: expected one of %s",
+			fmt.Sprint(value), bsonnav.DGetString(widget, "Name"), strings.Join(names, ", "))
+	}
+	if !bsonnav.DSet(widget, "RenderMode", string(mode)) {
+		return fmt.Errorf("container %q has no stored RenderMode property to set",
+			bsonnav.DGetString(widget, "Name"))
+	}
+	return nil
+}
+
 // setLegacyImageRefMut writes a static image's Image or a dynamic image's
 // DefaultImage: the qualified name of an image-collection entry as a plain
 // string ("" when unset), the key and shape CREATE writes and DESCRIBE reads

mdl/executor/cmd_pages_builder_v3.go

@@ -564,7 +564,7 @@ func (pb *pageBuilder) buildPluggable(def *WidgetDefinition, w *ast.WidgetV3) (p
 	if err := applyWidgetAppearance(widget, w, pb.themeRegistry); err != nil {
 		return nil, err
 	}
-	if err := applyPluggableSystemSettings(widget, w); err != nil {
+	if err := applyPluggableSystemSettings(widget, w, def); err != nil {
 		return nil, err
 	}
 	if err := pb.applyVisibleWhen(widget, w); err != nil {

mdl/executor/cmd_pages_builder_v3_layout.go

@@ -268,9 +268,19 @@ func (pb *pageBuilder) buildContainerV3(w *ast.WidgetV3) (*pages.Container, erro
 		},
 	}
 
-	// Handle RenderMode
+	// Handle RenderMode. The codec stores it verbatim, so an unknown member is
+	// refused here rather than written into a document Studio Pro cannot open.
 	if rm := w.GetRenderMode(); rm != "" {
-		container.RenderMode = pages.ContainerRenderMode(rm)
+		mode, ok := pages.CanonicalContainerRenderMode(rm)
+		if !ok {
+			names := make([]string, len(pages.ContainerRenderModes))
+			for i, m := range pages.ContainerRenderModes {
+				names[i] = string(m)
+			}
+			return nil, mdlerrors.NewValidationf("container %q: unknown RenderMode %q — valid modes are %s",
+				w.Name, rm, strings.Join(names, ", "))
+		}
+		container.RenderMode = mode
 	}
 
 	// Handle Action / OnClick property — a Container is clickable in Mendix via

mdl/executor/cmd_pages_describe_output.go

@@ -453,7 +453,11 @@ func outputWidgetMDLV3(ctx *ExecContext, w rawWidget, indent int) {
 
 	case "Forms$DivContainer", "Pages$DivContainer":
 		header := fmt.Sprintf("container %s", mdlIdent(w.Name))
-		props := appendAppearanceProps(ctx, nil, w)
+		var props []string
+		if w.RenderMode != "" && w.RenderMode != "Div" {
+			props = append(props, fmt.Sprintf("RenderMode: %s", w.RenderMode))
+		}
+		props = appendAppearanceProps(ctx, props, w)
 		if w.Action != "" {
 			props = append(props, actionProp("Action", w.Action))
 		}

mdl/executor/cmd_pages_describe_parse.go

@@ -257,6 +257,10 @@ func parseRawWidget(ctx *ExecContext, w map[string]any, parentEntityContext ...s
 			if onClick := asActionMap(w["OnClickAction"]); onClick != nil {
 				widget.Action = extractButtonAction(ctx, map[string]any{"Action": onClick})
 			}
+			// The HTML element it renders as (mendixlabs/mxcli#1582).
+			if rm, ok := w["RenderMode"].(string); ok {
+				widget.RenderMode = rm
+			}
 		}
 		// Extract GroupBox-specific properties
 		if typeName == "Forms$GroupBox" || typeName == "Pages$GroupBox" {

mdl/executor/cmd_pages_describe_pluggable.go

@@ -1313,6 +1313,22 @@ func extractExplicitProperties(ctx *ExecContext, w map[string]any) []rawExplicit
 			continue
 		}
 
+		// An expression property: its text, quoted. This path had no branch for
+		// one, so a stored expression was described as absent — the Calendar's
+		// `editable` and `showEventDate` (mendixlabs/mxcli#1578). Only an
+		// Expression-typed property is read: a value of another type keeps
+		// whatever its PrimitiveValue says below.
+		if valueTypes[typePointerID] == "Expression" {
+			if expr := extractString(value["Expression"]); expr != "" {
+				result = append(result, rawExplicitProp{
+					Key:       propKey,
+					Value:     expr,
+					ValueType: "Expression",
+				})
+			}
+			continue
+		}
+
 		// Check for a PrimitiveValue.
 		//
 		// Booleans used to be dropped here as "common defaults". They are not: