Merge pull request python#60 from mgmacias95/fix_nested_bug

Author: pablogsal

Lib/test/test_fstring.py

@@ -511,6 +511,11 @@ def test_mismatched_parens(self):
                             ])
         self.assertRaises(SyntaxError, eval, "f'{" + "("*500 + "}'")
 
+    def test_fstring_nested_too_deeply(self):
+        self.assertAllRaise(SyntaxError,
+                            "f-string: expressions nested too deeply",
+                            ['f"{1+2:{1+2:{1+1:{1}}}}"'])
+
     def test_double_braces(self):
         self.assertEqual(f'{{', '{')
         self.assertEqual(f'a{{', 'a{')
@@ -741,6 +746,7 @@ def test_parens_in_expressions(self):
         self.assertAllRaise(SyntaxError, 'unterminated string literal',
                             ["f'{\n}'",
                              ])
+
     def test_newlines_before_syntax_error(self):
         self.assertAllRaise(SyntaxError, "invalid syntax",
                 ["f'{.}'", "\nf'{.}'", "\n\nf'{.}'"])
@@ -1390,7 +1396,6 @@ def __repr__(self):
         #self.assertEqual(f'X{x =}Y', 'Xx\t='+repr(x)+'Y')
         #self.assertEqual(f'X{x =       }Y', 'Xx\t=\t'+repr(x)+'Y')
 
-
     def test_walrus(self):
         x = 20
         # This isn't an assignment expression, it's 'x', with a format

Parser/tokenizer.c

@@ -2458,6 +2458,10 @@ tok_get_fstring_mode(struct tok_state *tok, tokenizer_mode* current_tok, struct
 
     if ((start_char == '{' && peek1 != '{') || (start_char == '}' && peek1 != '}')) {
         if (start_char == '{') {
+            if (current_tok->bracket_mark_index >= MAX_EXPR_NEXTING) {
+                return MAKE_TOKEN(syntaxerror(tok, "f-string: expressions nested too deeply"));
+            }
+
             current_tok->bracket_mark[++current_tok->bracket_mark_index] = current_tok->bracket_stack;
         }
         tok->tok_mode_stack[tok->tok_mode_stack_index].kind = TOK_REGULAR_MODE;