fix LIKE ESCAPE with backslash

src/15utility.js

@@ -1196,6 +1196,15 @@ var domEmptyChildren = (utils.domEmptyChildren = function (container) {
  */
 var patternCache = {};
 var like = (utils.like = function (pattern, value, escape = '') {
+	// Normalize the escape character: the SQL ESCAPE clause specifies a single
+	// character, but due to JavaScript string escaping layers in the parser
+	// pipeline, a backslash escape can arrive as multiple backslash characters
+	// (e.g. '\\\\' for '\\', etc.). If the escape string consists entirely
+	// of backslashes, collapse it to a single '\\'.
+	if (escape.length > 1 && /^\\+$/.test(escape)) {
+		escape = '\\';
+	}
+
 	if (!patternCache[pattern]) {
 		var regexStr = '^'; // Start regex pattern to match from the beginning.
 		var i = 0; // Index for traversing the pattern string.
@@ -1205,7 +1214,7 @@ var like = (utils.like = function (pattern, value, escape = '') {
 			var nextChar = i < pattern.length - 1 ? pattern[i + 1] : '';
 
 			// Handle escape character.
-			if (currentChar === escape) {
+			if (escape && currentChar === escape) {
 				regexStr += '\\' + nextChar;
 				i++; // Skip next character as it's escaped.
 			}

test/test1978.js

@@ -0,0 +1,98 @@
+if (typeof exports === 'object') {
+	var assert = require('assert');
+	var alasql = require('..');
+} else {
+	__dirname = '.';
+}
+
+describe('Test 1978 - LIKE ESCAPE with backslash', function () {
+	it('supports backslash as ESCAPE character in utils.like', function (done) {
+		// Single backslash escape (the correct runtime value)
+		assert(alasql.utils.like('%\\%%', '100%', '\\'));
+		assert(!alasql.utils.like('%\\%%', '100', '\\'));
+
+		// Double backslash (arrives from parser escaping layer)
+		assert(alasql.utils.like('%\\%%', '100%', '\\\\'));
+		assert(!alasql.utils.like('%\\%%', '1000', '\\\\'));
+
+		// Triple and quadruple backslashes (additional escaping layers)
+		assert(alasql.utils.like('%\\%%', '100%', '\\\\\\'));
+		assert(!alasql.utils.like('%\\%%', '1000', '\\\\\\'));
+
+		assert(alasql.utils.like('%\\%%', '100%', '\\\\\\\\'));
+		assert(!alasql.utils.like('%\\%%', '1000', '\\\\\\\\'));
+
+		// Underscore wildcard escaping with backslash
+		assert(alasql.utils.like('%\\_%', '100_', '\\'));
+		assert(!alasql.utils.like('%\\_%', '1000', '\\'));
+
+		assert(alasql.utils.like('%\\_%', '100_', '\\\\'));
+		assert(!alasql.utils.like('%\\_%', '1000', '\\\\'));
+
+		done();
+	});
+
+	it('supports non-backslash ESCAPE characters in utils.like', function (done) {
+		// Caret escape
+		assert(alasql.utils.like('%^%%', '100%', '^'));
+		assert(!alasql.utils.like('%^%%', '100', '^'));
+
+		// Exclamation mark escape
+		assert(alasql.utils.like('%!%%', '100%', '!'));
+		assert(!alasql.utils.like('%!%%', '100', '!'));
+
+		// Tilde escape
+		assert(alasql.utils.like('%~_%', '100_', '~'));
+		assert(!alasql.utils.like('%~_%', '1000', '~'));
+
+		done();
+	});
+
+	it('supports backslash ESCAPE in SQL queries', function (done) {
+		alasql('CREATE TABLE cities1978 (city string, population string)');
+
+		alasql(
+			"INSERT INTO cities1978 VALUES ('%','1'), ('1%','2'), ('%1','3'), ('1%1','4'), ('_1','5'), ('1^1','6'), ('1!1','7')"
+		);
+
+		// Using backslash ESCAPE in SQL with two LIKE columns (the original issue)
+		var res = alasql(
+			"SELECT * FROM cities1978 WHERE (city LIKE '%\\%%' ESCAPE '\\\\') OR (population LIKE '2\\%' ESCAPE '\\\\') ORDER BY population DESC"
+		);
+
+		assert.deepStrictEqual(res, [
+			{city: '1%1', population: '4'},
+			{city: '%1', population: '3'},
+			{city: '1%', population: '2'},
+			{city: '%', population: '1'},
+		]);
+
+		// Also verify with quadruple backslashes in SQL ESCAPE
+		var resQuad = alasql(
+			"SELECT * FROM cities1978 WHERE (city LIKE '%\\%%' ESCAPE '\\\\\\\\') OR (population LIKE '2\\%' ESCAPE '\\\\\\\\') ORDER BY population DESC"
+		);
+
+		assert.deepStrictEqual(resQuad, [
+			{city: '1%1', population: '4'},
+			{city: '%1', population: '3'},
+			{city: '1%', population: '2'},
+			{city: '%', population: '1'},
+		]);
+
+		// Using caret ESCAPE (should also work with multiple LIKE columns)
+		var res2 = alasql(
+			"SELECT * FROM cities1978 WHERE (city LIKE '%^%%' ESCAPE '^') OR (population LIKE '2^%' ESCAPE '^') ORDER BY population DESC"
+		);
+
+		assert.deepStrictEqual(res2, [
+			{city: '1%1', population: '4'},
+			{city: '%1', population: '3'},
+			{city: '1%', population: '2'},
+			{city: '%', population: '1'},
+		]);
+
+		alasql('DROP TABLE cities1978');
+
+		done();
+	});
+});