From d66bc9e8a7a8d6774d912a4b9d151885c4d8de1d Mon Sep 17 00:00:00 2001
From: Lysandros Nikolaou <lisandrosnik@gmail.com>
Date: Tue, 15 Aug 2023 14:26:42 +0300
Subject: [PATCH] gh-107967: Fix infinite recursion on invalid escape sequence
 warning (#107968)

---
 Lib/test/test_fstring.py | 10 ++++++++++
 Parser/tokenizer.c       |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
index cb14bba2602..16f01973f99 100644
--- a/Lib/test/test_fstring.py
+++ b/Lib/test/test_fstring.py
@@ -1673,5 +1673,15 @@ print(f'''{{
         self.assertEqual(stdout.decode('utf-8').strip().replace('\r\n', '\n').replace('\r', '\n'),
                          "3\n=3")
 
+    def test_syntax_warning_infinite_recursion_in_file(self):
+        with temp_cwd():
+            script = 'script.py'
+            with open(script, 'w') as f:
+                f.write(r"print(f'\{1}')")
+
+            _, stdout, stderr = assert_python_ok(script)
+            self.assertIn(rb'\1', stdout)
+            self.assertEqual(len(stderr.strip().splitlines()), 2)
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Parser/tokenizer.c b/Parser/tokenizer.c
index 5a42f6f3573..b10c9f1f8ea 100644
--- a/Parser/tokenizer.c
+++ b/Parser/tokenizer.c
@@ -1539,6 +1539,9 @@ error:
 static int
 warn_invalid_escape_sequence(struct tok_state *tok, int first_invalid_escape_char)
 {
+    if (!tok->report_warnings) {
+        return 0;
+    }
 
     PyObject *msg = PyUnicode_FromFormat(
         "invalid escape sequence '\\%c'",