gh-121645: Add PyBytes_Join() function (#121646)

* Replace _PyBytes_Join() with PyBytes_Join().
* Keep _PyBytes_Join() as an alias to PyBytes_Join().

1 files changed, 40 insertions, 0 deletions

diff --git a/Lib/test/test_capi/test_bytes.py b/Lib/test/test_capi/test_bytes.py
index d5f047b..5908d79 100644
--- a/Lib/test/test_capi/test_bytes.py
+++ b/Lib/test/test_capi/test_bytes.py
@@ -249,6 +249,46 @@ class CAPITest(unittest.TestCase):
         # CRASHES resize(NULL, 0, False)
         # CRASHES resize(NULL, 3, False)
 
+    def test_join(self):
+        """Test PyBytes_Join()"""
+        bytes_join = _testcapi.bytes_join
+
+        self.assertEqual(bytes_join(b'', []), b'')
+        self.assertEqual(bytes_join(b'sep', []), b'')
+
+        self.assertEqual(bytes_join(b'', [b'a', b'b', b'c']), b'abc')
+        self.assertEqual(bytes_join(b'-', [b'a', b'b', b'c']), b'a-b-c')
+        self.assertEqual(bytes_join(b' - ', [b'a', b'b', b'c']), b'a - b - c')
+        self.assertEqual(bytes_join(b'-', [bytearray(b'abc'),
+                                           memoryview(b'def')]),
+                         b'abc-def')
+
+        self.assertEqual(bytes_join(b'-', iter([b'a', b'b', b'c'])), b'a-b-c')
+
+        # invalid 'sep' argument
+        with self.assertRaises(TypeError):
+            bytes_join(bytearray(b'sep'), [])
+        with self.assertRaises(TypeError):
+            bytes_join(memoryview(b'sep'), [])
+        with self.assertRaises(TypeError):
+            bytes_join('', [])  # empty Unicode string
+        with self.assertRaises(TypeError):
+            bytes_join('unicode', [])
+        with self.assertRaises(TypeError):
+            bytes_join(123, [])
+        with self.assertRaises(SystemError):
+            self.assertEqual(bytes_join(NULL, [b'a', b'b', b'c']), b'abc')
+
+        # invalid 'iterable' argument
+        with self.assertRaises(TypeError):
+            bytes_join(b'', [b'bytes', 'unicode'])
+        with self.assertRaises(TypeError):
+            bytes_join(b'', [b'bytes', 123])
+        with self.assertRaises(TypeError):
+            bytes_join(b'', 123)
+        with self.assertRaises(SystemError):
+            bytes_join(b'', NULL)
+
 
 if __name__ == "__main__":
     unittest.main()