Sync pre-release CPython 3.15 branch from GitHub (2026-06-22)

Summary:
Imported python/cpython `3.15.0b2+dev` from upstream rev [`a940f93`](https://www.github.com/python/cpython/commit/a940f933af981a90efbd81912091def59c8c2018) (committed 2026-06-22 00:29:07+00:00).

# Commit Info

- Base: (`3.15.0b2+dev`) - [`b83a217`](https://www.github.com/python/cpython/commit/b83a217558ee30c48a3aa08f0cb7c869f9c75e96) (commit date: 2026-06-19 23:31:12+00:00)
- Imported: (`3.15.0b2+dev`) - [`a940f93`](https://www.github.com/python/cpython/commit/a940f933af981a90efbd81912091def59c8c2018) (commit date: 2026-06-22 00:29:07+00:00)

# Noteworthy file changes

- Test files (3 added)
- Low-signal files (2 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GHebASlRhais1WkFADnU5_JYN-ANbr0LAAAz

Differential Revision: D109269832

fbshipit-source-id: bd221efe7947d2bdbce657312ac545499672959a

Author: generatedunixname1734921407115435

.readthedocs.yml

@@ -11,19 +11,21 @@ build:
   os: ubuntu-24.04
   tools:
     python: "3"
+  apt_packages:
+    - jq
 
   jobs:
-    post_checkout:
+    post_system_dependencies:
       # https://docs.readthedocs.com/platform/stable/guides/build/skip-build.html#skip-builds-based-on-conditions
       #
-      # Cancel building pull requests when there aren't changes in the Doc
+      # Cancel building pull requests when there are no changes in the Doc
       # directory or RTD configuration, or if we can't cleanly merge the base
       # branch.
       - |
         set -eEux;
         if [ "$READTHEDOCS_VERSION_TYPE" = "external" ];
         then
-          base_branch=main;
+          base_branch=$(wget -qO- "https://api.github.com/repos/python/cpython/pulls/$READTHEDOCS_VERSION" | jq -er ".base.ref");
           git fetch --depth=50 origin $base_branch:origin-$base_branch;
           for attempt in $(seq 10);
           do

Doc/glossary.rst

@@ -96,21 +96,24 @@ Glossary
       :meth:`~object.__aexit__` methods.  Introduced by :pep:`492`.
 
    asynchronous generator
-      A function which returns an :term:`asynchronous generator iterator`.  It
-      looks like a coroutine function defined with :keyword:`async def` except
-      that it contains :keyword:`yield` expressions for producing a series of
-      values usable in an :keyword:`async for` loop.
-
-      Usually refers to an asynchronous generator function, but may refer to an
-      *asynchronous generator iterator* in some contexts.  In cases where the
-      intended meaning isn't clear, using the full terms avoids ambiguity.
+      Informally used to mean either an :term:`asynchronous generator
+      function` or an :term:`asynchronous generator iterator`, depending on
+      context.  The formal terms :term:`asynchronous generator function` and
+      :term:`asynchronous generator iterator` are uncommon in practice;
+      "asynchronous generator" alone is almost always sufficient.
+
+   asynchronous generator function
+      A function which returns an :term:`asynchronous generator iterator`.
+      It looks like a coroutine function defined with :keyword:`async def`
+      except that it contains :keyword:`yield` expressions for producing a
+      series of values usable in an :keyword:`async for` loop.  See :pep:`525`.
 
       An asynchronous generator function may contain :keyword:`await`
       expressions as well as :keyword:`async for`, and :keyword:`async with`
       statements.
 
    asynchronous generator iterator
-      An object created by an :term:`asynchronous generator` function.
+      An object created by an :term:`asynchronous generator function`.
 
       This is an :term:`asynchronous iterator` which when called using the
       :meth:`~object.__anext__` method returns an awaitable object which will execute
@@ -641,23 +644,33 @@ Glossary
       .. index:: single: generator
 
    generator
-      A function which returns a :term:`generator iterator`.  It looks like a
-      normal function except that it contains :keyword:`yield` expressions
-      for producing a series of values usable in a for-loop or that can be
-      retrieved one at a time with the :func:`next` function.
+      Informally used to mean either a :term:`generator function` or a
+      :term:`generator iterator`, depending on context.  The formal terms
+      :term:`generator function` and :term:`generator iterator` are uncommon
+      in practice; "generator" alone is almost always sufficient.
 
-      Usually refers to a generator function, but may refer to a
-      *generator iterator* in some contexts.  In cases where the intended
-      meaning isn't clear, using the full terms avoids ambiguity.
+      .. index:: single: generator function
+
+   generator function
+      A function which returns a :term:`generator` object.  It looks like a
+      normal function except that it contains :keyword:`yield` expressions
+      for producing a series of values usable in a :keyword:`for`\-loop or
+      that can be retrieved one at a time with the :func:`next` function.
+      See :ref:`yieldexpr`.
 
    generator iterator
-      An object created by a :term:`generator` function.
+      An object created by a :term:`generator function` or a
+      :term:`generator expression`.
 
       Each :keyword:`yield` temporarily suspends processing, remembering the
-      execution state (including local variables and pending
-      try-statements).  When the *generator iterator* resumes, it picks up where
-      it left off (in contrast to functions which start fresh on every
-      invocation).
+      execution state (including local variables and pending try-statements).
+      When the *generator iterator* resumes, it picks up where it left off
+      (in contrast to functions which start fresh on every invocation).
+
+      Generator iterators also implement the :meth:`~generator.send` method
+      to send a value into the suspended generator, and the
+      :meth:`~generator.throw` method to raise an exception at the point
+      where the generator was paused.  See :ref:`generator-methods`.
 
       .. index:: single: generator expression
 

Doc/library/dialog.rst

@@ -15,16 +15,31 @@ The :mod:`!tkinter.simpledialog` module contains convenience classes and
 functions for creating simple modal dialogs to get a value from the user.
 
 
-.. function:: askfloat(title, prompt, **kw)
-              askinteger(title, prompt, **kw)
-              askstring(title, prompt, **kw)
+.. function:: askfloat(title, prompt, *, initialvalue=None, minvalue=None, maxvalue=None, parent=None)
+              askinteger(title, prompt, *, initialvalue=None, minvalue=None, maxvalue=None, parent=None)
+              askstring(title, prompt, *, initialvalue=None, show=None, parent=None)
 
-   The above three functions provide dialogs that prompt the user to enter a value
-   of the desired type.
+   Prompt the user to enter a value of the desired type and return it, or
+   ``None`` if the dialog is cancelled.
+
+   *title* is the dialog title and *prompt* the message shown above the entry.
+   *initialvalue* is the value initially placed in the entry.
+   *parent* is the window over which the dialog is shown.
+   :func:`askinteger` and :func:`askfloat` also accept *minvalue* and
+   *maxvalue*, which bound the accepted value.
+   :func:`askstring` also accepts *show*, a character used to mask the entered
+   text, for example ``'*'`` to hide a password.
 
 .. class:: Dialog(parent, title=None)
 
    The base class for custom dialogs.
+   Instantiating it shows the dialog modally and returns once the user closes
+   it; the entered value is then available in the :attr:`!result` attribute.
+
+   .. attribute:: result
+
+      The value produced by :meth:`apply`, or ``None`` if the dialog was
+      cancelled.
 
    .. method:: body(master)
 
@@ -46,7 +61,8 @@ functions for creating simple modal dialogs to get a value from the user.
 
    .. method:: apply()
 
-      Process the data entered by the user.
+      Process the data entered by the user, for example by storing it in the
+      :attr:`!result` attribute.
       Called after :meth:`validate` succeeds and just before the dialog is
       destroyed.
       The default implementation does nothing; override it to act on or store

Lib/_pydatetime.py

@@ -55,7 +55,7 @@ def _days_before_year(year):
 
 def _days_in_month(year, month):
     "year, month -> number of days in that month in that year."
-    assert 1 <= month <= 12, month
+    assert 1 <= month <= 12, f"month must be in 1..12, not {month}"
     if month == 2 and _is_leap(year):
         return 29
     return _DAYS_IN_MONTH[month]
@@ -1987,7 +1987,7 @@ def fromisoformat(cls, date_string):
                 if became_next_day:
                     year, month, day = date_components
                     # Only wrap day/month when it was previously valid
-                    if month <= 12 and day <= (days_in_month := _days_in_month(year, month)):
+                    if 1 <= month <= 12 and day <= (days_in_month := _days_in_month(year, month)):
                         # Calculate midnight of the next day
                         day += 1
                         if day > days_in_month:

Lib/inspect.py

@@ -2720,6 +2720,10 @@ def __init__(self, name, kind, *, default=_empty, annotation=_empty):
                 raise ValueError(msg)
             self._kind = _POSITIONAL_ONLY
             name = 'implicit{}'.format(name[1:])
+        elif name == '.format':
+            # gh-151665: Hidden parameter of compiler-generated annotation and type
+            # alias/typevar evaluators. Show it as "format".
+            name = 'format'
 
         # It's possible for C functions to have a positional-only parameter
         # where the name is a keyword, so for compatibility we'll allow it.

Lib/test/datetimetester.py

@@ -3773,6 +3773,7 @@ def test_fromisoformat_fails_datetime_valueerror(self):
             "2009-04-01T12:30:90",          # Second out of range
             "2009-04-01T12:90:45",          # Minute out of range
             "2009-04-01T25:30:45",          # Hour out of range
+            "2009-00-01T24:00:00",          # Month below range
             "2009-13-01T24:00:00",          # Month out of range
             "9999-12-31T24:00:00",          # Year out of range
         ]

Lib/test/test_tkinter/test_dnd.py

@@ -0,0 +1,98 @@
+import unittest
+import tkinter
+from tkinter import dnd
+from test.support import requires
+from test.test_tkinter.support import setUpModule  # noqa: F401
+from test.test_tkinter.support import AbstractTkTest
+
+requires('gui')
+
+
+class Target:
+    def __init__(self, widget, log):
+        self.widget = widget
+        self.log = log
+        widget.dnd_accept = self.dnd_accept
+
+    def dnd_accept(self, source, event):
+        self.log.append('accept')
+        return self
+
+    def dnd_enter(self, source, event):
+        self.log.append('enter')
+
+    def dnd_motion(self, source, event):
+        self.log.append('motion')
+
+    def dnd_leave(self, source, event):
+        self.log.append('leave')
+
+    def dnd_commit(self, source, event):
+        self.log.append('commit')
+
+
+class Source:
+    def __init__(self, log):
+        self.log = log
+
+    def dnd_end(self, target, event):
+        self.log.append('end')
+
+
+class FakeEvent:
+    def __init__(self, widget, num=1):
+        self.num = num
+        self.widget = widget
+        self.x = self.y = self.x_root = self.y_root = 0
+
+
+class DndTest(AbstractTkTest, unittest.TestCase):
+
+    def setUp(self):
+        super().setUp()
+        self.canvas = tkinter.Canvas(self.root)
+        self.canvas.pack()
+        # on_motion() locates the target with winfo_containing().  Bypass that
+        # real screen lookup, which depends on the window being visible and
+        # unobscured, so the test does not hinge on the window manager.
+        self.canvas.winfo_containing = lambda x, y: self.canvas
+        self.log = []
+        self.source = Source(self.log)
+        self.target = Target(self.canvas, self.log)
+
+    def test_drag_and_drop(self):
+        handler = dnd.dnd_start(self.source, FakeEvent(self.canvas))
+        self.assertIsNotNone(handler)
+        handler.on_motion(FakeEvent(self.canvas))  # Enter the target.
+        handler.on_motion(FakeEvent(self.canvas))  # Move within the target.
+        handler.on_release(FakeEvent(self.canvas))  # Drop on the target.
+        self.assertEqual(self.log,
+                         ['accept', 'enter', 'accept', 'motion', 'commit', 'end'])
+
+    def test_cancel(self):
+        handler = dnd.dnd_start(self.source, FakeEvent(self.canvas))
+        handler.on_motion(FakeEvent(self.canvas))  # Enter the target.
+        handler.cancel()  # Leaves the target without committing.
+        self.assertEqual(self.log, ['accept', 'enter', 'leave', 'end'])
+
+    def test_no_target(self):
+        # Nothing under the pointer accepts the drag.
+        self.canvas.winfo_containing = lambda x, y: None
+        handler = dnd.dnd_start(self.source, FakeEvent(self.canvas))
+        handler.on_motion(FakeEvent(self.canvas))
+        handler.on_release(FakeEvent(self.canvas))
+        self.assertEqual(self.log, ['end'])
+
+    def test_no_recursive_start(self):
+        handler = dnd.dnd_start(self.source, FakeEvent(self.canvas))
+        self.assertIsNotNone(handler)
+        # A drag is already in progress, so a second start is ignored.
+        self.assertIsNone(dnd.dnd_start(self.source, FakeEvent(self.canvas)))
+        handler.cancel()
+
+    def test_high_button_number_ignored(self):
+        self.assertIsNone(dnd.dnd_start(self.source, FakeEvent(self.canvas, num=6)))
+
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_tkinter/test_filedialog.py

@@ -0,0 +1,73 @@
+import os
+import unittest
+from tkinter import filedialog
+from tkinter.commondialog import Dialog
+from test.support import requires, swap_attr
+from test.test_tkinter.support import setUpModule  # noqa: F401
+from test.test_tkinter.support import AbstractTkTest
+
+requires('gui')
+
+
+class NativeDialogTest(AbstractTkTest, unittest.TestCase):
+    # Open, SaveAs and Directory wrap modal native dialogs.  The _test_callback
+    # seam is called by show() just before the dialog would open; replacing it
+    # with a function that raises exercises show() without blocking on the
+    # dialog.
+
+    def check(self, dialog_class, command):
+        self.assertEqual(dialog_class.command, command)
+        master = None
+        def test_callback(dialog, parent):
+            nonlocal master
+            master = parent
+            raise ZeroDivisionError
+        with swap_attr(Dialog, '_test_callback', test_callback):
+            d = dialog_class(self.root, title='Test')
+            self.assertRaises(ZeroDivisionError, d.show)
+        self.assertIs(master, self.root)
+
+    def test_open(self):
+        self.check(filedialog.Open, 'tk_getOpenFile')
+
+    def test_saveas(self):
+        self.check(filedialog.SaveAs, 'tk_getSaveFile')
+
+    def test_directory(self):
+        self.check(filedialog.Directory, 'tk_chooseDirectory')
+
+
+class FileDialogTest(AbstractTkTest, unittest.TestCase):
+    # The pure-Python FileDialog runs its own modal loop in go(); its logic is
+    # exercised here without entering the loop.
+
+    def test_selection(self):
+        d = filedialog.FileDialog(self.root)
+        d.directory = os.path.abspath(os.sep)
+        d.set_selection('spam.txt')
+        self.assertEqual(os.path.basename(d.get_selection()), 'spam.txt')
+
+    def test_filter(self):
+        d = filedialog.FileDialog(self.root)
+        d.set_filter(os.getcwd(), '*.py')
+        self.assertEqual(d.get_filter(), (os.getcwd(), '*.py'))
+
+    def test_ok_cancel(self):
+        d = filedialog.FileDialog(self.root)
+        d.directory = os.getcwd()
+        d.set_selection('spam.txt')
+        d.ok_command()  # Accepts the current selection.
+        self.assertEqual(os.path.basename(d.how), 'spam.txt')
+        d.cancel_command()  # Returns no selection.
+        self.assertIsNone(d.how)
+
+    def test_subclasses(self):
+        for cls in filedialog.LoadFileDialog, filedialog.SaveFileDialog:
+            with self.subTest(cls=cls.__name__):
+                d = cls(self.root)
+                self.assertIsInstance(d, filedialog.FileDialog)
+                self.assertEqual(d.top.title(), cls.title)
+
+
+if __name__ == "__main__":
+    unittest.main()