Merge branch 'main' into pythongh-114847

Doc/library/datetime.rst

@@ -1079,6 +1079,24 @@ Other constructors, all class methods:
    time tuple.  See also :ref:`strftime-strptime-behavior` and
    :meth:`datetime.fromisoformat`.
 
+   .. versionchanged:: 3.13
+
+      If *format* specifies a day of month without a year a
+      :exc:`DeprecationWarning` is now emitted.  This is to avoid a quadrennial
+      leap year bug in code seeking to parse only a month and day as the
+      default year used in absence of one in the format is not a leap year.
+      Such *format* values may raise an error as of Python 3.15.  The
+      workaround is to always include a year in your *format*.  If parsing
+      *date_string* values that do not have a year, explicitly add a year that
+      is a leap year before parsing:
+
+      .. doctest::
+
+         >>> from datetime import datetime
+         >>> date_string = "02/29"
+         >>> when = datetime.strptime(f"{date_string};1984", "%m/%d;%Y")  # Avoids leap year bug.
+         >>> when.strftime("%B %d")  # doctest: +SKIP
+         'February 29'
 
 
 Class attributes:
@@ -2657,6 +2675,25 @@ Notes:
    for  formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, and ``%V``. Format ``%y`` does require a leading zero.
 
+(10)
+   When parsing a month and day using :meth:`~.datetime.strptime`, always
+   include a year in the format.  If the value you need to parse lacks a year,
+   append an explicit dummy leap year.  Otherwise your code will raise an
+   exception when it encounters leap day because the default year used by the
+   parser is not a leap year.  Users run into this bug every four years...
+
+   .. doctest::
+
+      >>> month_day = "02/29"
+      >>> datetime.strptime(f"{month_day};1984", "%m/%d;%Y")  # No leap year bug.
+      datetime.datetime(1984, 2, 29, 0, 0)
+
+   .. deprecated-removed:: 3.13 3.15
+      :meth:`~.datetime.strptime` calls using a format string containing
+      a day of month without a year now emit a
+      :exc:`DeprecationWarning`. In 3.15 or later we may change this into
+      an error or change the default year to a leap year. See :gh:`70647`.
+
 .. rubric:: Footnotes
 
 .. [#] If, that is, we ignore the effects of Relativity

Doc/library/unittest.rst

@@ -1880,8 +1880,8 @@ Loading and running tests
       Python identifiers) will be loaded.
 
       All test modules must be importable from the top level of the project. If
-      the start directory is not the top level directory then the top level
-      directory must be specified separately.
+      the start directory is not the top level directory then *top_level_dir*
+      must be specified separately.
 
       If importing a module fails, for example due to a syntax error, then
       this will be recorded as a single error and discovery will continue.  If
@@ -1901,9 +1901,11 @@ Loading and running tests
       package.
 
       The pattern is deliberately not stored as a loader attribute so that
-      packages can continue discovery themselves. *top_level_dir* is stored so
-      ``load_tests`` does not need to pass this argument in to
-      ``loader.discover()``.
+      packages can continue discovery themselves.
+
+      *top_level_dir* is stored internally, and used as a default to any
+      nested calls to ``discover()``. That is, if a package's ``load_tests``
+      calls ``loader.discover()``, it does not need to pass this argument.
 
       *start_dir* can be a dotted module name as well as a directory.
 
@@ -1930,6 +1932,9 @@ Loading and running tests
          *start_dir* can not be a :term:`namespace packages <namespace package>`.
          It has been broken since Python 3.7 and Python 3.11 officially remove it.
 
+      .. versionchanged:: 3.13
+         *top_level_dir* is only stored for the duration of *discover* call.
+
 
    The following attributes of a :class:`TestLoader` can be configured either by
    subclassing or assignment on an instance:

Include/internal/pycore_bytes_methods.h

@@ -32,8 +32,12 @@ extern PyObject *_Py_bytes_rfind(const char *str, Py_ssize_t len, PyObject *args
 extern PyObject *_Py_bytes_rindex(const char *str, Py_ssize_t len, PyObject *args);
 extern PyObject *_Py_bytes_count(const char *str, Py_ssize_t len, PyObject *args);
 extern int _Py_bytes_contains(const char *str, Py_ssize_t len, PyObject *arg);
-extern PyObject *_Py_bytes_startswith(const char *str, Py_ssize_t len, PyObject *args);
-extern PyObject *_Py_bytes_endswith(const char *str, Py_ssize_t len, PyObject *args);
+extern PyObject *_Py_bytes_startswith(const char *str, Py_ssize_t len,
+                                      PyObject *subobj, Py_ssize_t start,
+                                      Py_ssize_t end);
+extern PyObject *_Py_bytes_endswith(const char *str, Py_ssize_t len,
+                                    PyObject *subobj, Py_ssize_t start,
+                                    Py_ssize_t end);
 
 /* The maketrans() static method. */
 extern PyObject* _Py_bytes_maketrans(Py_buffer *frm, Py_buffer *to);

Lib/_strptime.py

@@ -10,6 +10,7 @@
     strptime -- Calculates the time struct represented by the passed-in string
 
 """
+import os
 import time
 import locale
 import calendar
@@ -250,12 +251,30 @@ def pattern(self, format):
         format = regex_chars.sub(r"\\\1", format)
         whitespace_replacement = re_compile(r'\s+')
         format = whitespace_replacement.sub(r'\\s+', format)
+        year_in_format = False
+        day_of_month_in_format = False
         while '%' in format:
             directive_index = format.index('%')+1
+            format_char = format[directive_index]
             processed_format = "%s%s%s" % (processed_format,
                                            format[:directive_index-1],
-                                           self[format[directive_index]])
+                                           self[format_char])
             format = format[directive_index+1:]
+            match format_char:
+                case 'Y' | 'y' | 'G':
+                    year_in_format = True
+                case 'd':
+                    day_of_month_in_format = True
+        if day_of_month_in_format and not year_in_format:
+            import warnings
+            warnings.warn("""\
+Parsing dates involving a day of month without a year specified is ambiguious
+and fails to parse leap day. The default behavior will change in Python 3.15
+to either always raise an exception or to use a different default year (TBD).
+To avoid trouble, add a specific year to the input & format.
+See https://github.com/python/cpython/issues/70647.""",
+                          DeprecationWarning,
+                          skip_file_prefixes=(os.path.dirname(__file__),))
         return "%s%s" % (processed_format, format)
 
     def compile(self, format):

Lib/collections/__init__.py

@@ -1038,9 +1038,9 @@ def __repr__(self):
         return f'{self.__class__.__name__}({", ".join(map(repr, self.maps))})'
 
     @classmethod
-    def fromkeys(cls, iterable, *args):
-        'Create a ChainMap with a single dict created from the iterable.'
-        return cls(dict.fromkeys(iterable, *args))
+    def fromkeys(cls, iterable, value=None, /):
+        'Create a new ChainMap with keys from iterable and values set to value.'
+        return cls(dict.fromkeys(iterable, value))
 
     def copy(self):
         'New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]'

Lib/ntpath.py

@@ -857,16 +857,19 @@ def commonpath(paths):
         drivesplits = [splitroot(p.replace(altsep, sep).lower()) for p in paths]
         split_paths = [p.split(sep) for d, r, p in drivesplits]
 
-        if len({r for d, r, p in drivesplits}) != 1:
-            raise ValueError("Can't mix absolute and relative paths")
-
         # Check that all drive letters or UNC paths match. The check is made only
         # now otherwise type errors for mixing strings and bytes would not be
         # caught.
         if len({d for d, r, p in drivesplits}) != 1:
             raise ValueError("Paths don't have the same drive")
 
         drive, root, path = splitroot(paths[0].replace(altsep, sep))
+        if len({r for d, r, p in drivesplits}) != 1:
+            if drive:
+                raise ValueError("Can't mix absolute and relative paths")
+            else:
+                raise ValueError("Can't mix rooted and not-rooted paths")
+
         common = path.split(sep)
         common = [c for c in common if c and c != curdir]
 

Lib/test/datetimetester.py

@@ -2793,6 +2793,19 @@ def test_strptime_single_digit(self):
                 newdate = strptime(string, format)
                 self.assertEqual(newdate, target, msg=reason)
 
+    def test_strptime_leap_year(self):
+        # GH-70647: warns if parsing a format with a day and no year.
+        with self.assertRaises(ValueError):
+            # The existing behavior that GH-70647 seeks to change.
+            self.theclass.strptime('02-29', '%m-%d')
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'.*day of month without a year.*'):
+            self.theclass.strptime('03-14.159265', '%m-%d.%f')
+        with self._assertNotWarns(DeprecationWarning):
+            self.theclass.strptime('20-03-14.159265', '%y-%m-%d.%f')
+        with self._assertNotWarns(DeprecationWarning):
+            self.theclass.strptime('02-29,2024', '%m-%d,%Y')
+
     def test_more_timetuple(self):
         # This tests fields beyond those tested by the TestDate.test_timetuple.
         t = self.theclass(2004, 12, 31, 6, 22, 33)

Lib/test/string_tests.py

@@ -1513,9 +1513,9 @@ def test_find_etc_raise_correct_error_messages(self):
                                 x, None, None, None)
         self.assertRaisesRegex(TypeError, r'^count\(', s.count,
                                 x, None, None, None)
-        self.assertRaisesRegex(TypeError, r'^startswith\(', s.startswith,
+        self.assertRaisesRegex(TypeError, r'^startswith\b', s.startswith,
                                 x, None, None, None)
-        self.assertRaisesRegex(TypeError, r'^endswith\(', s.endswith,
+        self.assertRaisesRegex(TypeError, r'^endswith\b', s.endswith,
                                 x, None, None, None)
 
         # issue #15534

Lib/test/support/__init__.py

@@ -1168,6 +1168,10 @@ def requires_limited_api(test):
         return unittest.skip('needs _testcapi and _testlimitedcapi modules')(test)
     return test
 
+
+TEST_MODULES_ENABLED = sysconfig.get_config_var('TEST_MODULES') == 'yes'
+
+
 def requires_specialization(test):
     return unittest.skipUnless(
         _opcode.ENABLE_SPECIALIZATION, "requires specialization")(test)

Lib/test/support/interpreters/__init__.py

@@ -73,7 +73,7 @@ def __str__(self):
 
 def create():
     """Return a new (idle) Python interpreter."""
-    id = _interpreters.create(isolated=True)
+    id = _interpreters.create(reqrefs=True)
     return Interpreter(id)
 
 
@@ -109,13 +109,13 @@ def __new__(cls, id, /):
             assert hasattr(self, '_ownsref')
         except KeyError:
             # This may raise InterpreterNotFoundError:
-            _interpreters._incref(id)
+            _interpreters.incref(id)
             try:
                 self = super().__new__(cls)
                 self._id = id
                 self._ownsref = True
             except BaseException:
-                _interpreters._deccref(id)
+                _interpreters.decref(id)
                 raise
             _known[id] = self
         return self
@@ -142,7 +142,7 @@ def _decref(self):
             return
         self._ownsref = False
         try:
-            _interpreters._decref(self.id)
+            _interpreters.decref(self.id)
         except InterpreterNotFoundError:
             pass
 

Lib/test/test__xxsubinterpreters.py

@@ -584,7 +584,7 @@ def f():
     def test_create_daemon_thread(self):
         with self.subTest('isolated'):
             expected = 'spam spam spam spam spam'
-            subinterp = interpreters.create(isolated=True)
+            subinterp = interpreters.create('isolated')
             script, file = _captured_script(f"""
                 import threading
                 def f():
@@ -604,7 +604,7 @@ def f():
             self.assertEqual(out, expected)
 
         with self.subTest('not isolated'):
-            subinterp = interpreters.create(isolated=False)
+            subinterp = interpreters.create('legacy')
             script, file = _captured_script("""
                 import threading
                 def f():

Lib/test/test_audit.py

@@ -89,6 +89,7 @@ def test_excepthook(self):
         )
 
     def test_unraisablehook(self):
+        import_helper.import_module("_testcapi")
         returncode, events, stderr = self.run_python("test_unraisablehook")
         if returncode:
             self.fail(stderr)