feat: make datagrid columns addressable in ALTER PAGE via dotted refs

Add widgetRef grammar rule supporting dotted notation (grid.column) in
ALTER PAGE operations. Columns inside DataGrid2 are now targetable for
SET, INSERT, DROP, and REPLACE using their derived name (attribute short
name or caption).

Grammar: widgetRef = identifier DOT identifier | identifier
AST: WidgetRef type replaces plain string widget references
Finder: findBsonColumn navigates Object.Properties["columns"].Objects[]
        and derives column names matching DESCRIBE output

Example:
  ALTER PAGE Mod.List { DROP WIDGET dgProducts.OldCol };
  ALTER PAGE Mod.List { SET Caption = 'New' ON dgProducts.Name };

Closes #113

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

mdl/ast/ast_alter_page.go

@@ -20,34 +20,55 @@ type AlterPageOperation interface {
 	isAlterPageOperation()
 }
 
-// SetPropertyOp represents: SET prop = value ON widgetName
-// or SET prop = value (page-level, WidgetName empty)
+// WidgetRef represents a widget reference, optionally with a sub-element path.
+// Plain: "btnSave" (Widget="btnSave", Column="")
+// Dotted: "dgProducts.Name" (Widget="dgProducts", Column="Name")
+type WidgetRef struct {
+	Widget string // widget name (always set)
+	Column string // column name within widget (empty for plain widget refs)
+}
+
+// Name returns the full reference string for error messages.
+func (r WidgetRef) Name() string {
+	if r.Column != "" {
+		return r.Widget + "." + r.Column
+	}
+	return r.Widget
+}
+
+// IsColumn returns true if this is a column reference (dotted path).
+func (r WidgetRef) IsColumn() bool {
+	return r.Column != ""
+}
+
+// SetPropertyOp represents: SET prop = value ON widgetRef
+// or SET prop = value (page-level, Target.Widget empty)
 type SetPropertyOp struct {
-	WidgetName string                 // empty for page-level SET
+	Target     WidgetRef              // empty Widget for page-level SET
 	Properties map[string]interface{} // property name -> value
 }
 
 func (s *SetPropertyOp) isAlterPageOperation() {}
 
-// InsertWidgetOp represents: INSERT AFTER/BEFORE widgetName { widgets }
+// InsertWidgetOp represents: INSERT AFTER/BEFORE widgetRef { widgets }
 type InsertWidgetOp struct {
-	Position   string // "AFTER" or "BEFORE"
-	TargetName string // widget to insert relative to
-	Widgets    []*WidgetV3
+	Position string    // "AFTER" or "BEFORE"
+	Target   WidgetRef // widget/column to insert relative to
+	Widgets  []*WidgetV3
 }
 
 func (s *InsertWidgetOp) isAlterPageOperation() {}
 
-// DropWidgetOp represents: DROP WIDGET name1, name2, ...
+// DropWidgetOp represents: DROP WIDGET ref1, ref2, ...
 type DropWidgetOp struct {
-	WidgetNames []string
+	Targets []WidgetRef
 }
 
 func (s *DropWidgetOp) isAlterPageOperation() {}
 
-// ReplaceWidgetOp represents: REPLACE widgetName WITH { widgets }
+// ReplaceWidgetOp represents: REPLACE widgetRef WITH { widgets }
 type ReplaceWidgetOp struct {
-	WidgetName string
+	Target     WidgetRef
 	NewWidgets []*WidgetV3
 }
 

mdl/executor/alter_page_test.go

@@ -95,7 +95,7 @@ func TestApplyDropWidget_Single(t *testing.T) {
 	w3 := makeWidget("txtPhone", "Pages$TextBox")
 	rawData := makeRawPage(w1, w2, w3)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtEmail"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtEmail"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -126,7 +126,7 @@ func TestApplyDropWidget_Multiple(t *testing.T) {
 	w3 := makeWidget("c", "Pages$TextBox")
 	rawData := makeRawPage(w1, w2, w3)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"a", "c"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "a"}, {Widget: "c"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -150,7 +150,7 @@ func TestApplyDropWidget_NotFound(t *testing.T) {
 	w1 := makeWidget("txtName", "Pages$TextBox")
 	rawData := makeRawPage(w1)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"nonexistent"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "nonexistent"}}}
 	err := applyDropWidget(rawData, op)
 	if err == nil {
 		t.Fatal("Expected error for nonexistent widget")
@@ -163,7 +163,7 @@ func TestApplyDropWidget_Nested(t *testing.T) {
 	container := makeContainerWidget("ctn1", inner1, inner2)
 	rawData := makeRawPage(container)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtInner1"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtInner1"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -186,7 +186,7 @@ func TestApplySetProperty_Name(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "txtOld",
+		Target: ast.WidgetRef{Widget: "txtOld"},
 		Properties: map[string]interface{}{
 			"Name": "txtNew",
 		},
@@ -211,7 +211,7 @@ func TestApplySetProperty_ButtonStyle(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "btnSave",
+		Target: ast.WidgetRef{Widget: "btnSave"},
 		Properties: map[string]interface{}{
 			"ButtonStyle": "Success",
 		},
@@ -234,7 +234,7 @@ func TestApplySetProperty_WidgetNotFound(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "nonexistent",
+		Target: ast.WidgetRef{Widget: "nonexistent"},
 		Properties: map[string]interface{}{
 			"Name": "new",
 		},
@@ -279,7 +279,7 @@ func TestApplySetProperty_PluggableWidget(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "cb1",
+		Target: ast.WidgetRef{Widget: "cb1"},
 		Properties: map[string]interface{}{
 			"showLabel": false,
 		},
@@ -448,7 +448,7 @@ func TestApplyDropWidget_Snippet(t *testing.T) {
 	w2 := makeWidget("txtEmail", "Pages$TextBox")
 	rawData := makeRawSnippet(w1, w2)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtEmail"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtEmail"}}}
 	if err := applyDropWidgetWith(rawData, op, findBsonWidgetInSnippet); err != nil {
 		t.Fatalf("applyDropWidgetWith failed: %v", err)
 	}
@@ -473,7 +473,7 @@ func TestApplySetProperty_Snippet(t *testing.T) {
 	rawData := makeRawSnippet(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "btnAction",
+		Target: ast.WidgetRef{Widget: "btnAction"},
 		Properties: map[string]interface{}{
 			"ButtonStyle": "Danger",
 		},