Iissue fixed #1740

src/50expression.js

@@ -689,14 +689,27 @@
 		}
 
 		toString() {
-			let s = this.columnid;
+			let s;
 
-			if (this.columnid == +this.columnid) {
+			// Check if columnid is an object with val and wrap properties (e.g., from bracket notation)
+			const isBracketedColumnId =
+				typeof this.columnid === 'object' &&
+				this.columnid !== null &&
+				this.columnid.val !== undefined;
+
+			if (isBracketedColumnId) {
+				const wrap = this.columnid.wrap;
+				const closeWrap = wrap === '[' ? ']' : '`';
+				s = wrap + this.columnid.val + closeWrap;
+			} else if (this.columnid == +this.columnid) {
 				s = '[' + this.columnid + ']';
+			} else {
+				s = this.columnid;
 			}
 
 			if (this.tableid) {
-				s = this.tableid + (this.columnid === +this.columnid ? '' : '.') + s;
+				const isNumericColumnId = this.columnid === +this.columnid;
+				s = this.tableid + (isNumericColumnId || isBracketedColumnId ? '' : '.') + s;
 
 				if (this.databaseid) {
 					s = this.databaseid + '.' + s;

src/alasqlparser.jison

@@ -356,7 +356,7 @@ Literal
 			else $$ = $1.toLowerCase();
 		}
 	| BRALITERAL
-		{ $$ = {val:doubleq($1.substr(1,$1.length-2)), wrap:$1.substr(0,1)}; }
+		{ $$ = {val:doubleq($1.substr(1,$1.length-2)), wrap:$1.substr(0,1)}; }
 	| error NonReserved
 		{ $$ = $2.toLowerCase() }
 	;

test/test1740.js

@@ -0,0 +1,44 @@
+if (typeof exports === 'object') {
+	var assert = require('assert');
+	var alasql = require('..');
+}
+
+describe('Test 1740 - Parse() then AST.toString() should restore square brackets on column names', function () {
+	const test = '1740';
+
+	it('A) Column name with space should preserve square brackets', function () {
+		var ast = alasql.parse('SELECT [Foo Bar] FROM tbl');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT [Foo Bar] FROM tbl');
+	});
+
+	it('B) Column name with period should preserve square brackets', function () {
+		var ast = alasql.parse('SELECT [Foo.Bar] FROM tbl');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT [Foo.Bar] FROM tbl');
+	});
+
+	it('C) Regular column name should not get square brackets', function () {
+		var ast = alasql.parse('SELECT FooBar FROM tbl');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT FooBar FROM tbl');
+	});
+
+	it('D) Multiple bracketed columns should all preserve square brackets', function () {
+		var ast = alasql.parse('SELECT [First Name], [Last Name], Age FROM users');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT [First Name], [Last Name], Age FROM users');
+	});
+
+	it('E) Bracketed column with special characters should preserve square brackets', function () {
+		var ast = alasql.parse('SELECT [Column!@#] FROM tbl');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT [Column!@#] FROM tbl');
+	});
+
+	it('F) Column name with backticks should preserve backticks', function () {
+		var ast = alasql.parse('SELECT `Foo Bar` FROM tbl');
+		var result = ast.toString();
+		assert.strictEqual(result, 'SELECT `Foo Bar` FROM tbl');
+	});
+});