fix: ALTER STYLING writes design properties on pages and snippets (#631)

.claude/skills/fix-issue.md

@@ -44,6 +44,7 @@ to the symptom table below, so the next similar issue costs fewer reads.
 | Studio Pro shows a dropdown / property as its default value even though MDL set it explicitly (e.g. CREATE ODATA CLIENT with `ConfigurationMicroflow:` set, but the "Configuration source" dropdown reads "Constants only") | The BSON key mxcli writes isn't what Studio Pro reads — either the key name is wrong, or multiple dropdown options actually share a single field discriminated by something other than the key name (return type of a referenced microflow, sibling property, etc.) | The `serializeXxx` function in `sdk/mpr/writer_*.go` for the affected document type | (1) Ask the user to duplicate the offending object in Studio Pro and **explicitly pick each dropdown option** on the duplicate(s). An unconfigured duplicate just looks like "Constants only" and tells you nothing about which field the option uses. (2) Re-dump the duplicates from `mprcontents/**/*.mxunit` **after every Studio Pro change** — cached `/tmp/svc-*.json` files go stale the instant the user edits the project (see [[feedback-refresh-bson-dumps]]). (3) Diff against mxcli's output to find the renamed key. (4) Don't assume one-state-per-key. The OData "Configuration microflow" / "Headers microflow" case stores BOTH options in the single `ConfigurationMicroflow` BSON field — Studio Pro picks the dropdown label from the referenced microflow's return type. When a discriminator like that exists, have both MDL keywords write to the same model field. Issues #573, #587 and 2026-05-27 unify-config-microflow fix |
 | `DESCRIBE` of a document type omits a property the user set in the CREATE (e.g. enum-level `/** doc */` vanishes after a roundtrip; `CREATE OR REPLACE` silently runs as plain CREATE for some types) — even though the AST struct has the field, the model has the field, the writer serialises it, and DESCRIBE prints it | Visitor never copied the parsed value into the AST struct — every layer below the visitor is wired but the visitor's `ExitCreateXxxStatement` is missing the assignment | `mdl/visitor/visitor_<type>.go` → `ExitCreateXxxStatement` | Diff the visitor against a known-good sibling (e.g. enumeration vs constant). Standard wiring: `stmt.Documentation = findDocCommentText(ctx)` for doc-comments; `if createStmt.OR() != nil && (createStmt.MODIFY() != nil \|\| createStmt.REPLACE() != nil) { stmt.CreateOrModify = true }` for OR MODIFY/REPLACE. When adding a new CREATE statement, grep `mdl/visitor/visitor_constant.go` and copy these two blocks verbatim. Issue #393 |
 | `create [or modify] association ... to System.X` passes `mxcli check --references` and `mxcli diff` but fails at `mxcli exec` with `child entity not found: System.X` | Two divergent entity resolvers: the write path's `findEntity` resolved the owning module via `h.FindModuleID(dm.ID)`, but the virtual System domain model is not a real unit, so the hierarchy walk yielded an empty module name and System entities never matched. The validation path (`buildEntityQualifiedNames`) keyed on `dm.ContainerID` and worked, hence the check-passes/exec-fails split | `mdl/executor/oql_type_inference.go` → `findEntity` | Resolve the module from `dm.ContainerID` (the module ID `BuildSystemDomainModel` sets), not by walking up from the DM's own unit ID. When a symptom is "passes check/diff but fails exec," suspect two resolvers and make the write-path one match the validation-path one; add an `exec`-level test, not just a `check` test. Issue #610 |
+| `ALTER STYLING ON PAGE/SNIPPET ... SET ...` fails with `unsupported container type: PAGE` (and `DESCRIBE STYLING` silently shows "No widgets found"); even past that, design-property writes never reached builder-created pages | Two layered bugs: (1) the visitor emits uppercase `ContainerType` `"PAGE"`/`"SNIPPET"` but `execAlterStyling`/`execDescribeStyling` compared lowercase, so it fell through to the unsupported-container error; (2) ALTER STYLING used the reflection walker `walkPageWidgets` (legacy `ListPages`/`UpdatePage`), which can't locate widgets in MDL-builder pages and violates the mutator-pattern rule | `mdl/executor/cmd_styling.go` (`execAlterStyling`, `execDescribeStyling`) + `mdl/backend/mpr/page_mutator.go` | Normalise container type with `strings.ToLower`. Route ALTER STYLING through `ctx.Backend.OpenPageForMutation(unitID)` like ALTER PAGE; check `mutator.FindWidget`. Add `SetDesignProperty`/`RemoveDesignProperty`/`ClearDesignProperties` to the `PageMutator` interface, writing the widget's `Appearance.DesignProperties` BSON array (`Forms$DesignPropertyValue` → `Toggle`/`Option`/`Custom` value), preserving an existing custom kind on option updates. When an ALTER uses a container-type discriminator, mirror the casing fix already done for ALTER PAGE (#402). Issue #631 |
 | `declare $x list of T = empty;` (or any list-typed `declare`) passes `mxcli check` but Studio Pro rejects with CE0053 ("type not allowed") + CE0038 ("value required") | `declare` maps to a Create Variable activity, which Mendix forbids from producing a list — but the validator only flagged an empty list *used as a loop source* (MDL002), never the declaration itself | `mdl/executor/validate_microflow.go` → `walkBody` `*ast.DeclareStmt` case | Emit `MDL040` (SeverityError) for any `stmt.Type.Kind == ast.TypeListOf`, regardless of initializer. Lists must come from a microflow parameter, a `retrieve`, or `$x = create list of T;`. Also fix the synced skills that present declare-list as valid (`write-microflows.md`, `cheatsheet-variables.md`, `check-syntax.md`, `patterns-*`). Issue #607 |
 
 ---

docs/01-project/MDL_FEATURE_MATRIX.md

@@ -187,7 +187,7 @@ Document types that exist in Mendix but have no MDL support:
 |---------|------|----------|--------|-----------|------|-------|----------|-------|---------|------|-----|--------|------|-----|------|--------|----------|-------|
 | **Microflow activities** | - | - | P | - | - | - | 02 | Y | P | P | P | Y | Y | - | - | - | P | 60+ activities supported; some edge cases missing |
 | **Building blocks** | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | Reusable page building blocks |
-| **Styling** | P | P | P | N | N | N | N | N | N | N | N | P | N | P | N | N | N | Class/Style/DesignProperties on widgets; full theme system not yet |
+| **Styling** | P | Y | P | N | N | Y | Y | Y | N | N | N | P | N | P | N | N | N | Class/Style/DesignProperties on widgets via ALTER STYLING (#631); full theme system not yet |
 | **Extensions** | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | Mendix extensions / add-ons |
 | **Custom JS actions** | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | JavaScript actions for nanoflows |
 | **Custom widgets** | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | Pluggable widget packages |

mdl-examples/bug-tests/631-alter-styling-design-properties.mdl

@@ -0,0 +1,67 @@
+-- ============================================================================
+-- Bug #631: ALTER STYLING cannot set design properties on widgets in pages
+--           and snippets
+-- ============================================================================
+--
+-- Symptom (before fix):
+--   `ALTER STYLING ON PAGE ... WIDGET ... SET ...` always failed with
+--   "unsupported container type: PAGE". The visitor stored ContainerType as
+--   uppercase "PAGE"/"SNIPPET" but the executor compared against lowercase, so
+--   it fell through to the unsupported-container error. The same casing bug
+--   silently broke DESCRIBE STYLING. Even past the casing issue, ALTER STYLING
+--   used a reflection walker (walkPageWidgets) that could not locate widgets in
+--   pages created by the MDL builder, so there was no working write path for
+--   design properties.
+--
+-- After fix:
+--   ALTER STYLING normalises the container type and goes through the page
+--   mutator (OpenPageForMutation), which works uniformly on pages/snippets
+--   created in Studio Pro and by the MDL builder. The mutator gained
+--   SetDesignProperty / RemoveDesignProperty / ClearDesignProperties writing the
+--   widget's Appearance.DesignProperties BSON array.
+--
+-- Usage:
+--   mxcli exec mdl-examples/bug-tests/631-alter-styling-design-properties.mdl -p app.mpr
+--   Open in Studio Pro — the container shows the css class, inline style, and
+--   Atlas design properties (Spacing bottom = Large, Full width toggle).
+-- ============================================================================
+
+create module BugTest631;
+
+-- A builder-created page (the case the old reflection walker could not handle).
+create page BugTest631.P_Styling
+(
+  title: 'Styling Target',
+  layout: Atlas_Core.Atlas_Default
+)
+{
+  container ctnTarget (class: 'old-class') {
+    dynamictext txtHello (content: 'Hello')
+  }
+}
+
+-- Class + inline style
+ALTER STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget
+  SET Class = 'card card-bordered',
+      Style = 'padding: 24px;';
+
+-- Option (dropdown) design property
+ALTER STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget
+  SET 'Spacing bottom' = 'Large';
+
+-- Toggle design property ON
+ALTER STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget
+  SET 'Full width' = ON;
+
+-- Read back — should report the class, style, and both design properties
+DESCRIBE STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget;
+
+-- Toggle OFF removes the property again
+ALTER STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget
+  SET 'Full width' = OFF;
+
+-- Clear all design properties (Class/Style remain)
+ALTER STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget
+  CLEAR DESIGN PROPERTIES;
+
+DESCRIBE STYLING ON PAGE BugTest631.P_Styling WIDGET ctnTarget;

mdl-examples/doctype-tests/12-styling-examples.mdl

@@ -572,26 +572,38 @@ describe styling on snippet StyleTest.MySnippet widget ctnSnippet;
 -- Change Class, Style, or DesignProperties on a single widget without
 -- rewriting the entire page. This is a targeted, in-place update.
 
--- TODO: ALTER STYLING cannot find widgets in pages created by the MDL page builder
--- because walkPageWidgets traverses LayoutCall.Arguments but the page parser doesn't
--- fully reconstruct the widget tree when re-reading builder-created pages.
--- These commands work on pages originally created in Studio Pro.
-
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET Class = 'card card-bordered';
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET Style = 'padding: 24px; border-radius: 12px;';
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET 'Spacing bottom' = 'Large';
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET 'Full width' = ON;
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET 'Full width' = OFF;
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   SET Class = 'card card-bordered',
---       Style = 'padding: 24px;',
---       'Spacing bottom' = 'Large',
---       'Full width' = ON;
--- ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
---   CLEAR DESIGN PROPERTIES;
--- DESCRIBE STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader;
+-- ALTER STYLING goes through the page mutator (issue #631), so it works on
+-- pages created by the MDL builder as well as those authored in Studio Pro.
+
+-- Set a CSS class
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET Class = 'card card-bordered';
+
+-- Set an inline style
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET Style = 'padding: 24px; border-radius: 12px;';
+
+-- Set an option (dropdown) design property
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET 'Spacing bottom' = 'Large';
+
+-- Turn a toggle design property ON
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET 'Full width' = ON;
+
+-- Turn a toggle design property OFF (removes it)
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET 'Full width' = OFF;
+
+-- Combine Class, Style, and design properties in one statement
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  SET Class = 'card card-bordered',
+      Style = 'padding: 24px;',
+      'Spacing bottom' = 'Large',
+      'Full width' = ON;
+
+-- Remove all design properties from a widget
+ALTER STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader
+  CLEAR DESIGN PROPERTIES;
+
+DESCRIBE STYLING ON PAGE StyleTest.P006_Roundtrip WIDGET ctnHeader;

mdl/ast/ast_styling.go

@@ -37,6 +37,7 @@ func (s *AlterStylingStmt) isStatement() {}
 type StylingAssignment struct {
 	Property string // "Class", "Style", or design property key (e.g., "Spacing top")
 	Value    string // Value string (CSS class, style, or option name)
+	IsCSS    bool   // true when set via the CLASS/STYLE keyword (appearance), false for a quoted design-property key
 	IsToggle bool   // true for ON/OFF values
 	ToggleOn bool   // true for ON, false for OFF (only meaningful when IsToggle is true)
 }

mdl/backend/mock/mock_page_mutator.go

@@ -17,25 +17,28 @@ var _ backend.PageMutator = (*MockPageMutator)(nil)
 // nil error (never panics). ContainerType defaults to ContainerPage when unset;
 // all other methods return zero values.
 type MockPageMutator struct {
-	ContainerTypeFunc        func() backend.ContainerKind
-	SetWidgetPropertyFunc    func(widgetRef string, prop string, value any) error
-	SetWidgetDataSourceFunc  func(widgetRef string, ds pages.DataSource) error
-	SetColumnPropertyFunc    func(gridRef string, columnRef string, prop string, value any) error
-	InsertWidgetFunc         func(widgetRef string, columnRef string, position backend.InsertPosition, widgets []pages.Widget) error
-	DropWidgetFunc           func(refs []backend.WidgetRef) error
-	ReplaceWidgetFunc        func(widgetRef string, columnRef string, widgets []pages.Widget) error
-	InsertColumnsFunc        func(gridRef, afterColumnRef string, position backend.InsertPosition, columns []*backend.DataGridColumnSpec) error
-	ReplaceColumnFunc        func(gridRef, columnRef string, columns []*backend.DataGridColumnSpec) error
-	FindWidgetFunc           func(name string) bool
-	AddVariableFunc          func(name, dataType, defaultValue string) error
-	DropVariableFunc         func(name string) error
-	SetLayoutFunc            func(newLayout string, paramMappings map[string]string) error
-	SetPluggablePropertyFunc func(widgetRef string, propKey string, op backend.PluggablePropertyOp, ctx backend.PluggablePropertyContext) error
-	EnclosingEntityFunc      func(widgetRef string) string
+	ContainerTypeFunc              func() backend.ContainerKind
+	SetWidgetPropertyFunc          func(widgetRef string, prop string, value any) error
+	SetWidgetDataSourceFunc        func(widgetRef string, ds pages.DataSource) error
+	SetColumnPropertyFunc          func(gridRef string, columnRef string, prop string, value any) error
+	SetDesignPropertyFunc          func(widgetRef string, key string, valueType string, option string) error
+	RemoveDesignPropertyFunc       func(widgetRef string, key string) error
+	ClearDesignPropertiesFunc      func(widgetRef string) error
+	InsertWidgetFunc               func(widgetRef string, columnRef string, position backend.InsertPosition, widgets []pages.Widget) error
+	DropWidgetFunc                 func(refs []backend.WidgetRef) error
+	ReplaceWidgetFunc              func(widgetRef string, columnRef string, widgets []pages.Widget) error
+	InsertColumnsFunc              func(gridRef, afterColumnRef string, position backend.InsertPosition, columns []*backend.DataGridColumnSpec) error
+	ReplaceColumnFunc              func(gridRef, columnRef string, columns []*backend.DataGridColumnSpec) error
+	FindWidgetFunc                 func(name string) bool
+	AddVariableFunc                func(name, dataType, defaultValue string) error
+	DropVariableFunc               func(name string) error
+	SetLayoutFunc                  func(newLayout string, paramMappings map[string]string) error
+	SetPluggablePropertyFunc       func(widgetRef string, propKey string, op backend.PluggablePropertyOp, ctx backend.PluggablePropertyContext) error
+	EnclosingEntityFunc            func(widgetRef string) string
 	EnclosingEntityForChildrenFunc func(widgetRef string) string
-	WidgetScopeFunc          func() map[string]model.ID
-	ParamScopeFunc           func() (map[string]model.ID, map[string]string)
-	SaveFunc                 func() error
+	WidgetScopeFunc                func() map[string]model.ID
+	ParamScopeFunc                 func() (map[string]model.ID, map[string]string)
+	SaveFunc                       func() error
 }
 
 func (m *MockPageMutator) ContainerType() backend.ContainerKind {
@@ -66,6 +69,27 @@ func (m *MockPageMutator) SetColumnProperty(gridRef string, columnRef string, pr
 	return nil
 }
 
+func (m *MockPageMutator) SetDesignProperty(widgetRef string, key string, valueType string, option string) error {
+	if m.SetDesignPropertyFunc != nil {
+		return m.SetDesignPropertyFunc(widgetRef, key, valueType, option)
+	}
+	return nil
+}
+
+func (m *MockPageMutator) RemoveDesignProperty(widgetRef string, key string) error {
+	if m.RemoveDesignPropertyFunc != nil {
+		return m.RemoveDesignPropertyFunc(widgetRef, key)
+	}
+	return nil
+}
+
+func (m *MockPageMutator) ClearDesignProperties(widgetRef string) error {
+	if m.ClearDesignPropertiesFunc != nil {
+		return m.ClearDesignPropertiesFunc(widgetRef)
+	}
+	return nil
+}
+
 func (m *MockPageMutator) InsertWidget(widgetRef string, columnRef string, position backend.InsertPosition, widgets []pages.Widget) error {
 	if m.InsertWidgetFunc != nil {
 		return m.InsertWidgetFunc(widgetRef, columnRef, position, widgets)