From dfa352838861c60c1d011d4b073a105c8f9f183c Mon Sep 17 00:00:00 2001
From: Elijah Allen <56412012+eaallen@users.noreply.github.com>
Date: Tue, 21 Jul 2026 16:49:47 -0600
Subject: [PATCH] fix: support SQL-standard doubled quotes in string literals

MySQL/SQL allow escaping a quote inside a string by doubling it
(e.g. 'O''Hare'). The lexer only recognized backslash escapes, so
these literals were split into multiple STRING tokens and failed to
parse.

Update the STRING lexer rules to accept '' and "" inside quoted
strings, matching https://dev.mysql.com/doc/refman/5.7/en/string-literals.html

Co-authored-by: Cursor <cursoragent@cursor.com>
---
 src/sqlParser.jison |  4 ++--
 test/main.test.js   | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/sqlParser.jison b/src/sqlParser.jison
index 271c94a..8cc99ff 100644
--- a/src/sqlParser.jison
+++ b/src/sqlParser.jison
@@ -119,8 +119,8 @@ UNION                                                             return 'UNION'
 "}"                                                               return '}'
 ";"                                                               return ';'
 
-['](\\.|[^'])*[']                                                 return 'STRING'
-["](\\.|[^"])*["]                                                 return 'STRING'
+['](['][']|\\.|[^'])*[']                                          return 'STRING'
+["](["]["]|\\.|[^"])*["]                                          return 'STRING'
 [0][x][0-9a-fA-F]+                                                return 'HEX_NUMERIC'
 [-]?[0-9]+(\.[0-9]+)?                                             return 'NUMERIC'
 [-]?[0-9]+(\.[0-9]+)?[eE][-][0-9]+(\.[0-9]+)?                     return 'EXPONENT_NUMERIC'
diff --git a/test/main.test.js b/test/main.test.js
index 4bf50b6..13d8893 100644
--- a/test/main.test.js
+++ b/test/main.test.js
@@ -468,4 +468,15 @@ describe('select grammar support', function () {
     SELECT one.name, group_concat(j.value, ', ') FROM one, json_each(one.stringArray) AS j GROUP BY one.id
     `)
   })
+
+  it('support SQL-standard doubled quotes inside string literals', function () {
+    const ast = testParser("select * from t where name = 'O''Hare'");
+    assert.equal(ast.value.where.right.value, "'O''Hare'");
+
+    const astDouble = testParser('select * from t where name = "say ""hi"""');
+    assert.equal(astDouble.value.where.right.value, '"say ""hi"""');
+
+    // empty string and backslash escapes should keep working
+    testParser("select * from t where a = '' and b = 'O\\'Hare'");
+  })
 });