bpo-42986: Fix parser crash when reporting syntax errors in f-string with newlines (pythonGH-24279)

Author: pablogsal

Lib/test/test_fstring.py

@@ -664,6 +664,9 @@ 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'{.}'"])
 
     def test_backslashes_in_string_part(self):
         self.assertEqual(f'\t', '\t')

Misc/NEWS.d/next/Core and Builtins/2021-01-20-23-44-15.bpo-42986.sWoaGf.rst

@@ -0,0 +1,2 @@
+Fix parser crash when reporting syntax errors in f-string with newlines.
+Patch by Pablo Galindo.

Parser/pegen.c

@@ -454,7 +454,7 @@ _PyPegen_raise_error_known_location(Parser *p, PyObject *errtype,
            does not physically exist */
         assert(p->tok->fp == NULL || p->tok->fp == stdin || p->tok->done == E_EOF);
 
-        if (p->tok->lineno == lineno) {
+        if (p->tok->lineno <= lineno) {
             Py_ssize_t size = p->tok->inp - p->tok->buf;
             error_line = PyUnicode_DecodeUTF8(p->tok->buf, size, "replace");
         }