[3.12] gh-111380: Show SyntaxWarnings only once when parsing if invalid syntax is encouintered (GH-111381) (#111382)

gh-111380: Show SyntaxWarnings only once when parsing if invalid syntax is encouintered (GH-111381)
(cherry picked from commit 3d2f1f0b830d86f16f42c42b54d3ea4453dac318)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/test/test_string_literals.py b/Lib/test/test_string_literals.py
index 9b663c0..371e819 100644
--- a/Lib/test/test_string_literals.py
+++ b/Lib/test/test_string_literals.py
@@ -131,6 +131,18 @@ class TestLiterals(unittest.TestCase):
         self.assertEqual(exc.lineno, 1)
         self.assertEqual(exc.offset, 1)
 
+        # Check that the warning is raised ony once if there are syntax errors
+
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter('always', category=SyntaxWarning)
+            with self.assertRaises(SyntaxError) as cm:
+                eval("'\\e' $")
+            exc = cm.exception
+        self.assertEqual(len(w), 1)
+        self.assertEqual(w[0].category, SyntaxWarning)
+        self.assertRegex(str(w[0].message), 'invalid escape sequence')
+        self.assertEqual(w[0].filename, '<string>')
+
     def test_eval_str_invalid_octal_escape(self):
         for i in range(0o400, 0o1000):
             with self.assertWarns(SyntaxWarning):