Sync pre-release CPython main branch from GitHub (2026-06-16)

Summary:
Imported python/cpython `3.16.0a0` from upstream rev [`11f032f`](https://www.github.com/python/cpython/commit/11f032f904c8019b332a3c367f335e05cde63628) (committed 2026-06-16 04:51:39+00:00).

# Commit Info

- Base: (`3.16.0a0`) - [`d63c994`](https://www.github.com/python/cpython/commit/d63c9940f0bcc5497c42c6ac2768cdab02300e10) (commit date: 2026-06-14 19:17:45+00:00)
- Imported: (`3.16.0a0`) - [`11f032f`](https://www.github.com/python/cpython/commit/11f032f904c8019b332a3c367f335e05cde63628) (commit date: 2026-06-16 04:51:39+00:00)

# Noteworthy file changes

- Low-signal files (4 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GB6Fux96Df_zYSQFAIvSbAVtys1Ebr0LAAAz

Differential Revision: D108709491

fbshipit-source-id: 788e39065e47524d74e1f1ddb6d7c11b7e66f3ce

Author: generatedunixname1734921407115435

.editorconfig

@@ -1,11 +1,11 @@
 root = true
 
-[*.{py,c,cpp,h,js,rst,md,yml,yaml,gram}]
+[*.{py,c,cpp,h,js,rst,md,yml,yaml,toml,gram}]
 trim_trailing_whitespace = true
 insert_final_newline = true
 indent_style = space
 
-[*.{py,c,cpp,h,gram}]
+[*.{py,c,cpp,h,toml,gram}]
 indent_size = 4
 
 [*.rst]

Doc/library/mimetypes.rst

@@ -39,8 +39,8 @@ the information :func:`init` sets up.
    (e.g. :program:`compress` or :program:`gzip`). The encoding is suitable for use
    as a :mailheader:`Content-Encoding` header, **not** as a
    :mailheader:`Content-Transfer-Encoding` header. The mappings are table driven.
-   Encoding suffixes are case sensitive; type suffixes are first tried case
-   sensitively, then case insensitively.
+   Encoding suffixes are case-sensitive. Suffix mappings and type suffixes are
+   first tried case-sensitively, then case-insensitively.
 
    The optional *strict* argument is a flag specifying whether the list of known MIME types
    is limited to only the official types `registered with IANA
@@ -131,6 +131,8 @@ behavior of the module.
    is already known the extension will be added to the list of known extensions.
    Valid extensions are empty or start with a ``'.'``.
 
+   Registered lower-case extensions are matched case-insensitively.
+
    When *strict* is ``True`` (the default), the mapping will be added to the
    official MIME types, otherwise to the non-standard ones.
 
@@ -312,6 +314,8 @@ than one MIME-type database; it provides an interface similar to the one of the
       extension is already known, the new type will replace the old one. When the type
       is already known the extension will be added to the list of known extensions.
 
+      Registered lower-case extensions are matched case-insensitively.
+
       When *strict* is ``True`` (the default), the mapping will be added to the
       official MIME types, otherwise to the non-standard ones.
 

Include/internal/pycore_interp_structs.h

@@ -308,8 +308,6 @@ struct _import_runtime_state {
            Modules are added there and looked up in _imp.find_extension(). */
         struct _Py_hashtable_t *hashtable;
     } extensions;
-    /* Package context -- the full module name for package imports */
-    const char * pkgcontext;
 };
 
 struct _import_state {

Include/internal/pycore_object.h

@@ -830,9 +830,14 @@ _PyObject_IS_GC(PyObject *obj)
             && (type->tp_is_gc == NULL || type->tp_is_gc(obj)));
 }
 
-// Fast inlined version of PyObject_Hash()
-static inline Py_hash_t
-_PyObject_HashFast(PyObject *op)
+// Fast inlined version of PyObject_Hash(). Dictionaries are very
+// likely to include string keys (class and instance attributes,
+// json, ...) so we include a fast path for strings.
+// This function should not be used in a collection if str is not
+// very likely, since it is slower than PyObject_Hash() on types
+// other than str. See gh-137759.
+static inline Py_ALWAYS_INLINE Py_hash_t
+_PyObject_HashDictKey(PyObject *op)
 {
     if (PyUnicode_CheckExact(op)) {
         Py_hash_t hash = PyUnstable_Unicode_GET_CACHED_HASH(op);

Lib/mimetypes.py

@@ -86,6 +86,9 @@ def add_type(self, type, ext, strict=True):
         is already known the extension will be added
         to the list of known extensions.
 
+        Registered lower-case extensions are matched
+        case-insensitively.
+
         If strict is true, information will be added to
         list of standard types, else to the list of non-standard
         types.
@@ -172,23 +175,33 @@ def guess_file_type(self, path, *, strict=True):
 
     def _guess_file_type(self, path, strict, splitext):
         base, ext = splitext(path)
-        while (ext_lower := ext.lower()) in self.suffix_map:
-            base, ext = splitext(base + self.suffix_map[ext_lower])
+        while True:
+            if ext in self.suffix_map:
+                suffix = self.suffix_map[ext]
+            elif (ext_lower := ext.lower()) in self.suffix_map:
+                suffix = self.suffix_map[ext_lower]
+            else:
+                break
+            base, ext = splitext(base + suffix)
         # encodings_map is case sensitive
         if ext in self.encodings_map:
             encoding = self.encodings_map[ext]
             base, ext = splitext(base)
         else:
             encoding = None
-        ext = ext.lower()
+        ext_lower = ext.lower()
         types_map = self.types_map[True]
         if ext in types_map:
             return types_map[ext], encoding
+        if ext_lower in types_map:
+            return types_map[ext_lower], encoding
         elif strict:
             return None, encoding
         types_map = self.types_map[False]
         if ext in types_map:
             return types_map[ext], encoding
+        if ext_lower in types_map:
+            return types_map[ext_lower], encoding
         else:
             return None, encoding
 
@@ -386,6 +399,9 @@ def add_type(type, ext, strict=True):
     is already known the extension will be added
     to the list of known extensions.
 
+    Registered lower-case extensions are matched
+    case-insensitively.
+
     If strict is true, information will be added to
     list of standard types, else to the list of non-standard
     types.

Lib/site.py

@@ -505,6 +505,11 @@ def _exec_imports(self):
         # batch.  In that case, PEP 829 says the import lines are
         # suppressed in favor of the .start's entry points.
         for filename, imports in self._importexecs.items():
+            # Inject 'sitedir' local variable in the current frame for
+            # compatibility with Python 3.14. Especially, "-nspkg.pth" files
+            # generated by setuptools use: sys._getframe(1).f_locals['sitedir'].
+            sitedir = os.path.dirname(filename)
+
             # Given "/path/to/foo.pth", check whether "/path/to/foo.start" was
             # registered in this same batch.
             name, dot, pth = filename.rpartition(".")

Lib/test/support/__init__.py

@@ -3159,7 +3159,7 @@ def in_systemd_nspawn_sync_suppressed() -> bool:
         with open("/run/systemd/container", "rb") as fp:
             if fp.read().rstrip() != b"systemd-nspawn":
                 return False
-    except FileNotFoundError:
+    except (FileNotFoundError, PermissionError):
         return False
 
     # If systemd-nspawn is used, O_SYNC flag will immediately

Lib/test/test_asyncio/test_ssl.py

@@ -1544,6 +1544,9 @@ async def client(addr):
             # This triggers bug gh-115514, also tested using mocks in
             # test.test_asyncio.test_selector_events.SelectorSocketTransportTests.test_write_buffer_after_close
             socket_transport = writer.transport._ssl_protocol._transport
+            # connection_lost may have already cleared _transport.
+            if socket_transport is None:
+                return
 
             class SocketWrapper:
                 def __init__(self, sock) -> None:

Lib/test/test_ctypes/test_as_parameter.py

@@ -5,7 +5,7 @@
                     c_short, c_int, c_long, c_longlong,
                     c_byte, c_wchar, c_float, c_double,
                     ArgumentError)
-from test.support import import_helper, skip_if_sanitizer
+from test.support import import_helper, skip_if_sanitizer, skip_emscripten_stack_overflow
 _ctypes_test = import_helper.import_module("_ctypes_test")
 
 
@@ -193,6 +193,7 @@ class S8I(Structure):
                              (9*2, 8*3, 7*4, 6*5, 5*6, 4*7, 3*8, 2*9))
 
     @skip_if_sanitizer('requires deep stack', thread=True)
+    @skip_emscripten_stack_overflow()
     def test_recursive_as_param(self):
         class A:
             pass

Lib/test/test_ctypes/test_structures.py

@@ -299,9 +299,16 @@ class X(Structure):
         self.assertEqual(s.first, got.first)
         self.assertEqual(s.second, got.second)
 
+    @unittest.skipIf(support.is_wasm32, "wasm ABI is incompatible with test expectations")
     def _test_issue18060(self, Vector):
         # Regression tests for gh-62260
 
+        # This test passes a struct of two doubles by value to atan2(), whose C
+        # signature is atan2(double, double), so it only works on platforms
+        # where the abi of a function that takes a struct with two doubles
+        # matches the abi of a function that takes two doubles. The wasm32 ABI
+        # does not satisfy this condition and the test breaks.
+
         # The call to atan2() should succeed if the
         # class fields were correctly cloned in the
         # subclasses. Otherwise, it will segfault.