[3.6] bpo-29104: Fixed parsing backslashes in f-strings. (GH-490) (#1812)

(cherry picked from commit 0cd7a3f)

1 files changed, 14 insertions, 0 deletions

diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
index 708ed25b52..25730029ae 100644
--- a/Lib/test/test_fstring.py
+++ b/Lib/test/test_fstring.py
@@ -361,6 +361,20 @@ f'{a * x()}'"""
         self.assertEqual(f'2\x203', '2 3')
         self.assertEqual(f'\x203', ' 3')
 
+        with self.assertWarns(DeprecationWarning):  # invalid escape sequence
+            value = eval(r"f'\{6*7}'")
+        self.assertEqual(value, '\\42')
+        self.assertEqual(f'\\{6*7}', '\\42')
+        self.assertEqual(fr'\{6*7}', '\\42')
+
+        AMPERSAND = 'spam'
+        # Get the right unicode character (&), or pick up local variable
+        # depending on the number of backslashes.
+        self.assertEqual(f'\N{AMPERSAND}', '&')
+        self.assertEqual(f'\\N{AMPERSAND}', '\\Nspam')
+        self.assertEqual(fr'\N{AMPERSAND}', '\\Nspam')
+        self.assertEqual(f'\\\N{AMPERSAND}', '\\&')
+
     def test_misformed_unicode_character_name(self):
         # These test are needed because unicode names are parsed
         # differently inside f-strings.