manifest: delay import of `typing.ByteString` for py 3.14 support (issue6940) Since Python 2.7 and 3.5, `typing.ByteString` was defined as an alias for `bytes | bytearray | memoryview`, and `bytes` was also accepted as a shorthand for this, so we have `bytes` sprinkled all over the codebase. But then PEP-688 reversed all of that by deprecating `typing.ByteString` and its successor `collections.abc.ByteString` in Python 3.12 (as well as the `bytes` shorthand)[1], and removing it completely in Python 3.14. That leaves us with a couple of problems, namely defining something useful that spans py3.8-py3.13 and keeps pytype happy, and finding all of the instances where `bytes` doesn't really mean `bytes`. The current successor to all of this is `collections.abc.Buffer` in Python 3.12 (or `typing_extensions.Buffer` in previous versions). However, the current CI does type checking using Python 3.11 (so the former is not avaiable), and pytype has issues with importing `typing_extensions.Buffer`[2]. The good news is we don't need to deal with this mess immediately, since the type annotation evaluation is delayed to the type checking phase, and we're making no effort at supporting it in all supported versions of Python. So by delaying the import of this particular symbol, we can still use it for type checking purposes, but can start assessing Python 3.14 problems without doing a lot of extra work. Putting this on stable will allow people interested in 3.14 to work on it 4-5 extra months earlier (and apparently there's some interest). [1] https://peps.python.org/pep-0688/#no-special-meaning-for-bytes [2] https://github.com/google/pytype/issues/1772

--- a/mercurial/manifest.py	Wed Nov 27 00:13:27 2024 -0500
+++ b/mercurial/manifest.py	Mon Nov 25 18:56:39 2024 -0500
@@ -10,10 +10,10 @@
 import heapq
 import itertools
 import struct
+import typing
 import weakref
 
 from typing import (
-    ByteString,
     Callable,
     Collection,
     Dict,
@@ -51,6 +51,12 @@
     constants as revlog_constants,
 )
 
+if typing.TYPE_CHECKING:
+    from typing import (
+        ByteString,
+    )
+
+
 parsers = policy.importmod('parsers')
 propertycache = util.propertycache