Add DATAGRID mx check integration test (issue #6)

Validates that pages with DATAGRID widgets pass mx check after the
placeholder ID leak fix. Tests both explicit columns (0 errors) and
template defaults (expected attribute errors only, no structural errors).

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

Author: ako

mdl/executor/roundtrip_mxcheck_datagrid_test.go

@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build integration
+
+package executor
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mendixlabs/mxcli/mdl/ast"
+)
+
+// TestMxCheck_DataGridPage creates a page with a DATAGRID widget and verifies
+// mx check passes. This is a regression test for issue #6: DATAGRID was
+// completely unusable because placeholder IDs leaked during template
+// augmentation when the .mpk file added extra properties.
+func TestMxCheck_DataGridPage(t *testing.T) {
+	if !mxCheckAvailable() {
+		t.Skip("mx command not available")
+	}
+
+	env := setupTestEnv(t)
+	defer env.teardown()
+
+	// Create entity for the DataGrid
+	entityName := testModule + ".MxCheckDGItem"
+	env.registerCleanup("entity", entityName)
+
+	if err := env.executeMDL(`CREATE OR MODIFY PERSISTENT ENTITY ` + entityName + ` (
+		Name: String(100),
+		Description: String(500),
+		Active: Boolean DEFAULT true
+	);`); err != nil {
+		t.Fatalf("Failed to create entity: %v", err)
+	}
+
+	// Create page with DATAGRID using DATABASE datasource and columns
+	pageName := testModule + ".MxCheckDataGridPage"
+	env.registerCleanup("page", pageName)
+
+	createPageMDL := `CREATE PAGE ` + pageName + ` (
+		Title: 'DataGrid Check Test',
+		Layout: Atlas_Core.Atlas_Default
+	) {
+		LAYOUTGRID mainGrid {
+			ROW row1 {
+				COLUMN col1 (DesktopWidth: 12) {
+					DATAGRID dg (DataSource: DATABASE ` + entityName + `) {
+						COLUMN colName (Attribute: Name, Caption: 'Name')
+						COLUMN colDesc (Attribute: Description, Caption: 'Description')
+						COLUMN colActive (Attribute: Active, Caption: 'Active')
+					}
+				}
+			}
+		}
+	}`
+
+	if err := env.executeMDL(createPageMDL); err != nil {
+		t.Fatalf("Failed to create page with DATAGRID: %v", err)
+	}
+
+	// Disconnect to flush changes before mx check
+	env.executor.Execute(&ast.DisconnectStmt{})
+
+	// Run mx check
+	output, err := runMxCheck(t, env.projectPath)
+	if err != nil {
+		if strings.Contains(output, "error") || strings.Contains(output, "Error") {
+			t.Errorf("mx check found errors for DATAGRID page:\n%s", output)
+		} else {
+			t.Logf("mx check output:\n%s", output)
+		}
+	} else {
+		t.Logf("mx check passed for DATAGRID page:\n%s", output)
+	}
+}
+
+// TestMxCheck_DataGridNoColumns creates a DATAGRID without explicit columns
+// (uses template defaults) and verifies the page is created successfully.
+// Note: template default columns reference attributes that don't exist on the
+// test entity, so mx check will report CE errors about missing attributes.
+// The key validation is that the page is created without placeholder ID leaks.
+func TestMxCheck_DataGridNoColumns(t *testing.T) {
+	if !mxCheckAvailable() {
+		t.Skip("mx command not available")
+	}
+
+	env := setupTestEnv(t)
+	defer env.teardown()
+
+	entityName := testModule + ".MxCheckDGNoColItem"
+	env.registerCleanup("entity", entityName)
+
+	if err := env.executeMDL(`CREATE OR MODIFY PERSISTENT ENTITY ` + entityName + ` (
+		Code: String(50),
+		Value: Integer
+	);`); err != nil {
+		t.Fatalf("Failed to create entity: %v", err)
+	}
+
+	pageName := testModule + ".MxCheckDGNoColPage"
+	env.registerCleanup("page", pageName)
+
+	createPageMDL := `CREATE PAGE ` + pageName + ` (
+		Title: 'DataGrid No Columns Test',
+		Layout: Atlas_Core.Atlas_Default
+	) {
+		LAYOUTGRID mainGrid {
+			ROW row1 {
+				COLUMN col1 (DesktopWidth: 12) {
+					DATAGRID dg (DataSource: DATABASE ` + entityName + `)
+				}
+			}
+		}
+	}`
+
+	if err := env.executeMDL(createPageMDL); err != nil {
+		t.Fatalf("Failed to create page with DATAGRID (no columns): %v", err)
+	}
+
+	// Disconnect to flush changes before mx check
+	env.executor.Execute(&ast.DisconnectStmt{})
+
+	// Run mx check — template default columns won't match the entity's attributes,
+	// so CE errors about missing attributes are expected. But placeholder ID leaks
+	// or structural errors (CE0463) would indicate a regression.
+	output, err := runMxCheck(t, env.projectPath)
+	if err != nil {
+		if strings.Contains(output, "placeholder") || strings.Contains(output, "CE0463") {
+			t.Errorf("mx check found structural errors (possible placeholder leak):\n%s", output)
+		} else {
+			t.Logf("mx check output (attribute errors expected for template defaults):\n%s", output)
+		}
+	} else {
+		t.Logf("mx check passed for DATAGRID (no columns) page:\n%s", output)
+	}
+}