Add test for NULL values in INTO SQL() - confirms issue exists

Co-authored-by: mathiasrw <[email protected]>

Author: Copilot

test/test042_null_issue.js

@@ -0,0 +1,73 @@
+if (typeof exports === 'object') {
+	var assert = require('assert');
+	var alasql = require('..');
+}
+
+describe('Test 042 - NULL values in INTO SQL()', function () {
+	it('1. Should output NULL for null values', function (done) {
+		var data = [
+			{a: 1, b: 'test', c: null, d: 3},
+			{a: 2, b: null, c: 4, d: null},
+			{a: null, b: 'value', c: null, d: null},
+		];
+		var res = alasql('SELECT * INTO SQL({tableid:"test_table"}) FROM ?', [data]);
+		
+		console.log('Generated SQL:');
+		console.log(res);
+		
+		// Check that NULL appears in the output instead of empty values
+		assert(res.indexOf('NULL') > -1, 'Output should contain NULL keyword');
+		
+		// Check that we don't have consecutive commas (,,) which indicate missing values
+		assert(res.indexOf(',,') === -1, 'Output should not contain consecutive commas (,,)');
+		
+		// Verify specific patterns for NULL values
+		// First row: c should be NULL
+		assert(res.indexOf('(1,\'test\',NULL,3)') > -1, 'First row should have NULL for c');
+		
+		// Second row: b and d should be NULL
+		assert(res.indexOf('(2,NULL,4,NULL)') > -1, 'Second row should have NULL for b and d');
+		
+		// Third row: a, c, and d should be NULL
+		assert(res.indexOf('(NULL,\'value\',NULL,NULL)') > -1, 'Third row should have NULL for a, c, and d');
+		
+		done();
+	});
+	
+	it('2. Should handle undefined values as NULL', function (done) {
+		var data = [
+			{a: 1, b: 'test'},
+			{a: 2, b: undefined, c: 4},
+		];
+		var res = alasql('SELECT * INTO SQL({tableid:"test_table"}) FROM ?', [data]);
+		
+		console.log('Generated SQL with undefined:');
+		console.log(res);
+		
+		// Check that NULL appears in the output
+		assert(res.indexOf('NULL') > -1, 'Output should contain NULL keyword for undefined values');
+		
+		// Check that we don't have consecutive commas
+		assert(res.indexOf(',,') === -1, 'Output should not contain consecutive commas (,,)');
+		
+		done();
+	});
+	
+	it('3. Should handle mixed NULL, undefined, and empty strings', function (done) {
+		var data = [
+			{a: 1, b: '', c: null, d: undefined},
+		];
+		var res = alasql('SELECT * INTO SQL({tableid:"test_table"}) FROM ?', [data]);
+		
+		console.log('Generated SQL with mixed values:');
+		console.log(res);
+		
+		// Empty string should remain as empty string
+		assert(res.indexOf("''") > -1, 'Empty string should be preserved as \'\'');
+		
+		// null and undefined should become NULL
+		assert(res.indexOf('NULL') > -1, 'null and undefined should become NULL');
+		
+		done();
+	});
+});