gh-100050: Fix an assertion error when raising unclosed parenthesis errors in the tokenizer (GH-100065)

(cherry picked from commit 97e7004)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
Automerge-Triggered-By: GH:pablogsal

Author: miss-islington

Lib/test/test_syntax.py

@@ -2095,6 +2095,22 @@ def test_error_parenthesis(self):
         for paren in ")]}":
             self._check_error(paren + "1 + 2", f"unmatched '\\{paren}'")
 
+        # Some more complex examples:
+        code = """\
+func(
+    a=["unclosed], # Need a quote in this comment: "
+    b=2,
+)
+"""
+        self._check_error(code, "parenthesis '\\)' does not match opening parenthesis '\\['")
+
+    def test_error_string_literal(self):
+
+        self._check_error("'blech", "unterminated string literal")
+        self._check_error('"blech', "unterminated string literal")
+        self._check_error("'''blech", "unterminated triple-quoted string literal")
+        self._check_error('"""blech', "unterminated triple-quoted string literal")
+
     def test_invisible_characters(self):
         self._check_error('print\x17("Hello")', "invalid non-printable character")
 

Misc/NEWS.d/next/Core and Builtins/2022-12-06-22-24-01.gh-issue-100050.lcrPqQ.rst

@@ -0,0 +1,2 @@
+Honor existing errors obtained when searching for mismatching parentheses in
+the tokenizer. Patch by Pablo Galindo

Parser/pegen_errors.c

@@ -170,6 +170,10 @@ _PyPegen_tokenize_full_source_to_check_for_errors(Parser *p) {
         const char *end;
         switch (_PyTokenizer_Get(p->tok, &start, &end)) {
             case ERRORTOKEN:
+                if (PyErr_Occurred()) {
+                    ret = -1;
+                    goto exit;
+                }
                 if (p->tok->level != 0) {
                     int error_lineno = p->tok->parenlinenostack[p->tok->level-1];
                     if (current_err_line > error_lineno) {