gh-104016: Fixed off by 1 error in f string tokenizer (#104047)

Co-authored-by: sunmy2019 <59365878+sunmy2019@users.noreply.github.com>
Co-authored-by: Ken Jin <kenjin@python.org>
Co-authored-by: Pablo Galindo <pablogsal@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
index 5e94c99..5c5176d 100644
--- a/Lib/test/test_fstring.py
+++ b/Lib/test/test_fstring.py
@@ -565,7 +565,23 @@ x = (
         self.assertAllRaise(SyntaxError,
                             "f-string: expressions nested too deeply",
                             ['f"{1+2:{1+2:{1+1:{1}}}}"'])
+        
+        def create_nested_fstring(n):
+            if n == 0:
+                return "1+1"
+            prev = create_nested_fstring(n-1)
+            return f'f"{{{prev}}}"'
 
+        self.assertAllRaise(SyntaxError,
+                            "too many nested f-strings",
+                            [create_nested_fstring(160)])
+    
+    def test_syntax_error_in_nested_fstring(self):
+        # See gh-104016 for more information on this crash
+        self.assertAllRaise(SyntaxError,
+                            "invalid syntax",
+                            ['f"{1 1:' + ('{f"1:' * 199)])
+    
     def test_double_braces(self):
         self.assertEqual(f'{{', '{')
         self.assertEqual(f'a{{', 'a{')