improvements

Author: AlexWaygood

Lib/_collections_abc.py

@@ -1168,5 +1168,6 @@ def __getattr__(attr):
     if attr == "ByteString":
         import warnings
         warnings._deprecated("collections.abc.ByteString", remove=(3, 17))
+        globals()["ByteString"] = _deprecated_ByteString
         return _deprecated_ByteString
     raise AttributeError(f"module 'collections.abc' has no attribute {attr!r}")

Lib/test/libregrtest/refleak.py

@@ -96,7 +96,8 @@ def runtest_refleak(test_name, test_func,
     # `ByteString` is not included in `collections.abc.__all__`
     with warnings.catch_warnings(action='ignore', category=DeprecationWarning):
         ByteString = collections.abc.ByteString
-    for obj in ByteString.__subclasses__() + [ByteString]:
+    # Mypy doesn't even think `ByteString` is a class, hence the `type: ignore`
+    for obj in ByteString.__subclasses__() + [ByteString]:  # type: ignore[attr-defined]
         abcs[obj] = _get_dump(obj)[0]
 
     # bpo-31217: Integer pool to get a single integer object for the same

Lib/test/test_collections.py

@@ -1936,6 +1936,12 @@ def assert_index_same(seq1, seq2, index_args):
                             nativeseq, seqseq, (letter, start, stop))
 
     def test_ByteString(self):
+        previous_sys_modules = sys.modules.copy()
+        self.addCleanup(sys.modules.update, previous_sys_modules)
+
+        for module in "collections", "_collections_abc", "collections.abc":
+            sys.modules.pop(module, None)
+
         with self.assertWarns(DeprecationWarning):
             from collections.abc import ByteString
         for sample in [bytes, bytearray]:

Lib/typing.py

@@ -3783,7 +3783,14 @@ def __getattr__(attr):
     elif attr == "ByteString":
         import warnings
 
-        warnings._deprecated("typing.ByteString", remove=(3, 17))
+        warnings._deprecated(
+            "typing.ByteString",
+            message=(
+                "{name!r} and 'collections.abc.ByteString' are deprecated "
+                "and slated for removal in Python {remove}"
+            ),
+            remove=(3, 17)
+        )
 
         class _DeprecatedGenericAlias(_SpecialGenericAlias, _root=True):
             def __init__(