fix: OVERVIEW_PAGE value bug, datasource ordering, Caption validation

- Fix SetPropertyWithEntity for OVERVIEW_PAGE: pass entity value instead
  of empty string (was clearing AdminPage instead of setting it)
- Split OVERVIEW_PAGE and PARAMETER handling in cmd_alter_workflow.go
- Reorder Build(): auto-datasource before applyChildSlots so entityContext
  is available for child widgets
- Validate slot.Operation in applyChildSlots (must be "widgets")
- setWidgetCaption returns validation error when Caption missing
  (matching setWidgetContent behavior)
- extractBinaryIDFromDoc handles []byte in addition to primitive.Binary

Author: retran

mdl/executor/bson_helpers.go

@@ -111,10 +111,14 @@ func dSetArray(doc bson.D, key string, elements []any) {
 
 // extractBinaryIDFromDoc extracts a binary ID string from a bson.D field.
 func extractBinaryIDFromDoc(val any) string {
-	if bin, ok := val.(primitive.Binary); ok {
+	switch bin := val.(type) {
+	case primitive.Binary:
 		return types.BlobToUUID(bin.Data)
+	case []byte:
+		return types.BlobToUUID(bin)
+	default:
+		return ""
 	}
-	return ""
 }
 
 // ============================================================================
@@ -352,8 +356,7 @@ func setRawWidgetProperty(widget bson.D, propName string, value interface{}) err
 func setWidgetCaption(widget bson.D, value interface{}) error {
 	caption := dGetDoc(widget, "Caption")
 	if caption == nil {
-		setTranslatableText(widget, "Caption", value)
-		return nil
+		return mdlerrors.NewValidation("widget has no Caption property")
 	}
 	setTranslatableText(caption, "", value)
 	return nil

mdl/executor/cmd_alter_workflow.go

@@ -62,7 +62,17 @@ func execAlterWorkflow(ctx *ExecContext, s *ast.AlterWorkflowStmt) error {
 		switch o := op.(type) {
 		case *ast.SetWorkflowPropertyOp:
 			switch o.Property {
-			case "OVERVIEW_PAGE", "PARAMETER":
+			case "OVERVIEW_PAGE":
+				// OVERVIEW_PAGE uses Entity as the page qualified name (Value is unused).
+				qn := o.Entity.Module + "." + o.Entity.Name
+				if qn == "." {
+					qn = ""
+				}
+				if err := mutator.SetPropertyWithEntity(o.Property, qn, qn); err != nil {
+					return mdlerrors.NewBackend("SET "+o.Property, err)
+				}
+			case "PARAMETER":
+				// PARAMETER uses Value as the variable name and Entity as the entity qualified name.
 				qn := o.Entity.Module + "." + o.Entity.Name
 				if qn == "." {
 					qn = ""

mdl/executor/widget_engine.go

@@ -129,12 +129,9 @@ func (e *PluggableWidgetEngine) Build(def *WidgetDefinition, w *ast.WidgetV3) (*
 		}
 	}
 
-	// 4. Apply child slots (.def.json)
-	if err := e.applyChildSlots(builder, slots, w, propertyTypeIDs); err != nil {
-		return nil, err
-	}
-
-	// 4.1 Auto datasource: map AST DataSource to first DataSource-type property.
+	// 4. Auto datasource: map AST DataSource to first DataSource-type property.
+	// This must run before child slots so that entityContext is available
+	// for child widgets that depend on the parent's data source.
 	dsHandledByMapping := false
 	for _, m := range mappings {
 		if m.Source == "DataSource" {
@@ -160,6 +157,11 @@ func (e *PluggableWidgetEngine) Build(def *WidgetDefinition, w *ast.WidgetV3) (*
 		}
 	}
 
+	// 4.1 Apply child slots (.def.json)
+	if err := e.applyChildSlots(builder, slots, w, propertyTypeIDs); err != nil {
+		return nil, err
+	}
+
 	// 4.3 Auto child slots: match AST children to Widgets-type template properties.
 	handledSlotKeys := make(map[string]bool)
 	for _, s := range slots {
@@ -525,6 +527,9 @@ func (e *PluggableWidgetEngine) applyChildSlots(builder backend.WidgetObjectBuil
 		}
 
 		ctx := &BuildContext{}
+		if slot.Operation != "widgets" {
+			return mdlerrors.NewValidationf("childSlots operation must be %q, got %q for property %s", "widgets", slot.Operation, slot.PropertyKey)
+		}
 		if err := e.applyOperation(builder, slot.Operation, slot.PropertyKey, ctx); err != nil {
 			return err
 		}