Sync pre-release CPython 3.15 branch from GitHub (2026-05-27)

Summary:
Imported python/cpython `3.15.0b1+` from upstream rev [`f216c89`](https://www.github.com/python/cpython/commit/f216c8963139bf858415e2d09cf938d3e29558df) (committed 2026-05-27 21:47:03+00:00).

# Commit Info

- Base: (`3.15.0b1+`) - [`528356e`](https://www.github.com/python/cpython/commit/528356eac0adf70fed0cf37dbb04c8fd529672d8) (commit date: 2026-05-26 19:46:16+00:00)
- Imported: (`3.15.0b1+`) - [`f216c89`](https://www.github.com/python/cpython/commit/f216c8963139bf858415e2d09cf938d3e29558df) (commit date: 2026-05-27 21:47:03+00:00)

# Noteworthy file changes

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

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GKATbSjgTT7ZlgMKAIdnxsR05dULbr0LAAAz

Differential Revision: D106605961

fbshipit-source-id: f2f8e2f0db848426a9e4cf3817f91860ae84965c

Author: generatedunixname1734921407115435

Doc/reference/compound_stmts.rst

@@ -620,7 +620,7 @@ The match statement is used for pattern matching.  Syntax:
    match_stmt: 'match' `subject_expr` ":" NEWLINE INDENT `case_block`+ DEDENT
    subject_expr: `flexible_expression` "," [`flexible_expression_list` [',']]
                : | `assignment_expression`
-   case_block: 'case' `patterns` [`guard`] ":" `!block`
+   case_block: 'case' `patterns` [`guard`] ":" `suite`
 
 .. note::
    This section uses single quotes to denote

Lib/test/test_perf_profiler.py

@@ -34,6 +34,21 @@ def supports_trampoline_profiling():
     raise unittest.SkipTest("perf trampoline profiling not supported")
 
 
+def _perf_env(**env_vars):
+    env = os.environ.copy()
+    # Keep perf's output stable regardless of the builder's perf config.
+    env.update(
+        {
+            "DEBUGINFOD_URLS": "",
+            "PERF_CONFIG": os.devnull,
+        }
+    )
+    if env_vars:
+        env.update(env_vars)
+    env["PYTHON_JIT"] = "0"
+    return env
+
+
 class TestPerfTrampoline(unittest.TestCase):
     def setUp(self):
         super().setUp()
@@ -63,13 +78,12 @@ def baz():
                 """
         with temp_dir() as script_dir:
             script = make_script(script_dir, "perftest", code)
-            env = {**os.environ, "PYTHON_JIT": "0"}
             with subprocess.Popen(
                 [sys.executable, "-Xperf", script],
                 text=True,
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE,
-                env=env,
+                env=_perf_env(),
             ) as process:
                 stdout, stderr = process.communicate()
 
@@ -132,13 +146,12 @@ def baz():
                 """
         with temp_dir() as script_dir:
             script = make_script(script_dir, "perftest", code)
-            env = {**os.environ, "PYTHON_JIT": "0"}
             with subprocess.Popen(
                 [sys.executable, "-Xperf", script],
                 text=True,
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE,
-                env=env,
+                env=_perf_env(),
             ) as process:
                 stdout, stderr = process.communicate()
 
@@ -198,13 +211,12 @@ def test_trampoline_works_after_fork_with_many_code_objects(self):
                 """
         with temp_dir() as script_dir:
             script = make_script(script_dir, "perftest", code)
-            env = {**os.environ, "PYTHON_JIT": "0"}
             with subprocess.Popen(
                 [sys.executable, "-Xperf", script],
                 text=True,
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE,
-                env=env,
+                env=_perf_env(),
             ) as process:
                 stdout, stderr = process.communicate()
 
@@ -242,13 +254,12 @@ def baz():
                 code = set_eval_hook + code
             with temp_dir() as script_dir:
                 script = make_script(script_dir, "perftest", code)
-                env = {**os.environ, "PYTHON_JIT": "0"}
                 with subprocess.Popen(
                     [sys.executable, script],
                     text=True,
                     stderr=subprocess.PIPE,
                     stdout=subprocess.PIPE,
-                    env=env,
+                    env=_perf_env(),
                 ) as process:
                     stdout, stderr = process.communicate()
 
@@ -345,9 +356,12 @@ def perf_command_works():
                 "-c",
                 'print("hello")',
             )
-            env = {**os.environ, "PYTHON_JIT": "0"}
             stdout = subprocess.check_output(
-                cmd, cwd=script_dir, text=True, stderr=subprocess.STDOUT, env=env
+                cmd,
+                cwd=script_dir,
+                text=True,
+                stderr=subprocess.STDOUT,
+                env=_perf_env(),
             )
         except (subprocess.SubprocessError, OSError):
             return False
@@ -359,43 +373,49 @@ def perf_command_works():
 
 
 def run_perf(cwd, *args, use_jit=False, **env_vars):
-    env = os.environ.copy()
-    if env_vars:
-        env.update(env_vars)
-    env["PYTHON_JIT"] = "0"
+    env = _perf_env(**env_vars)
     output_file = cwd + "/perf_output.perf"
-    if not use_jit:
-        base_cmd = (
-            "perf",
-            "record",
-            "--no-buildid",
-            "--no-buildid-cache",
-            "-g",
-            "--call-graph=fp",
-            "-o", output_file,
-            "--"
-        )
+    base_cmd = [
+        "perf",
+        "record",
+        "--no-buildid",
+        "--no-buildid-cache",
+        "-g",
+        "--call-graph=dwarf,65528" if use_jit else "--call-graph=fp",
+    ]
+    if use_jit:
+        perf_commands = []
+        # Some builders have low perf_event_mlock_kb limits.
+        mmap_sizes = ("4M", "2M", "1M", "512K", "256K", "128K", None)
+        for mmap_size in mmap_sizes:
+            command = base_cmd.copy()
+            if mmap_size is not None:
+                command += ["-F99", "-k1", "-m", mmap_size]
+            else:
+                command += ["-F99", "-k1"]
+            command += ["-o", output_file, "--"]
+            perf_commands.append(command)
     else:
-        base_cmd = (
-            "perf",
-            "record",
-            "--no-buildid",
-            "--no-buildid-cache",
-            "-g",
-            "--call-graph=dwarf,65528",
-            "-F99",
-            "-k1",
-            "-o",
-            output_file,
-            "--",
+        perf_commands = [base_cmd + ["-o", output_file, "--"]]
+
+    mmap_pages_error = "try again with a smaller value of -m/--mmap_pages"
+    for index, base_cmd in enumerate(perf_commands):
+        proc = subprocess.run(
+            base_cmd + list(args),
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            env=env,
+            text=True,
         )
-    proc = subprocess.run(
-        base_cmd + args,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE,
-        env=env,
-        text=True,
-    )
+        if (
+            proc.returncode
+            and use_jit
+            and index != len(perf_commands) - 1
+            and mmap_pages_error in proc.stderr
+        ):
+            continue
+        break
+
     if proc.returncode:
         print(proc.stderr, file=sys.stderr)
         raise ValueError(f"Perf failed with return code {proc.returncode}")
@@ -425,54 +445,77 @@ def run_perf(cwd, *args, use_jit=False, **env_vars):
 
 
 class TestPerfProfilerMixin:
-    def run_perf(self, script_dir, perf_mode, script):
+    PERF_CAPTURE_ATTEMPTS = 3
+
+    def run_perf(self, script_dir, script, activate_trampoline=True):
         raise NotImplementedError()
 
+    def run_perf_with_retries(
+        self, script_dir, script, expected_symbols=(), activate_trampoline=True
+    ):
+        stdout = stderr = ""
+        for _ in range(self.PERF_CAPTURE_ATTEMPTS):
+            stdout, stderr = self.run_perf(
+                script_dir, script, activate_trampoline=activate_trampoline
+            )
+            if activate_trampoline and any(
+                symbol not in stdout for symbol in expected_symbols
+            ):
+                continue
+            break
+        return stdout, stderr
+
     def test_python_calls_appear_in_the_stack_if_perf_activated(self):
         with temp_dir() as script_dir:
             code = """if 1:
+                from itertools import repeat
+
                 def foo(n):
-                    x = 0
-                    for i in range(n):
-                        x += i
+                    for _ in repeat(None, n):
+                        pass
 
                 def bar(n):
                     foo(n)
 
                 def baz(n):
                     bar(n)
 
-                baz(10000000)
+                baz(40000000)
                 """
             script = make_script(script_dir, "perftest", code)
-            stdout, stderr = self.run_perf(script_dir, script)
-            self.assertEqual(stderr, "")
+            expected_symbols = [
+                f"py::foo:{script}",
+                f"py::bar:{script}",
+                f"py::baz:{script}",
+            ]
+            stdout, _ = self.run_perf_with_retries(
+                script_dir, script, expected_symbols
+            )
 
-            self.assertIn(f"py::foo:{script}", stdout)
-            self.assertIn(f"py::bar:{script}", stdout)
-            self.assertIn(f"py::baz:{script}", stdout)
+            for expected_symbol in expected_symbols:
+                self.assertIn(expected_symbol, stdout)
 
     def test_python_calls_do_not_appear_in_the_stack_if_perf_deactivated(self):
         with temp_dir() as script_dir:
             code = """if 1:
+                from itertools import repeat
+
                 def foo(n):
-                    x = 0
-                    for i in range(n):
-                        x += i
+                    for _ in repeat(None, n):
+                        pass
 
                 def bar(n):
                     foo(n)
 
                 def baz(n):
                     bar(n)
 
-                baz(10000000)
+                baz(40000000)
                 """
             script = make_script(script_dir, "perftest", code)
-            stdout, stderr = self.run_perf(
+            stdout, _ = self.run_perf_with_retries(
                 script_dir, script, activate_trampoline=False
             )
-            self.assertEqual(stderr, "")
 
             self.assertNotIn(f"py::foo:{script}", stdout)
             self.assertNotIn(f"py::bar:{script}", stdout)
@@ -542,13 +585,12 @@ def compile_trampolines_for_all_functions():
 
         with temp_dir() as script_dir:
             script = make_script(script_dir, "perftest", code)
-            env = {**os.environ, "PYTHON_JIT": "0"}
             with subprocess.Popen(
                 [sys.executable, "-Xperf", script],
                 universal_newlines=True,
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE,
-                env=env,
+                env=_perf_env(),
             ) as process:
                 stdout, stderr = process.communicate()
 

Lib/test/test_xml_etree.py

@@ -3657,6 +3657,32 @@ def test_basic(self):
         doc = ET.XML("<root>a&amp;<sub>b&amp;</sub>c&amp;</root>")
         self.assertEqual(''.join(doc.itertext()), 'a&b&c&')
 
+    def test_comment(self):
+        e = ET.Element('root')
+        e.text = 'before'
+        comment = ET.Comment('comment')
+        self.assertEqual(comment.text, 'comment')
+        comment.tail = 'after'
+        e.append(comment)
+        self.assertEqual(''.join(e.itertext()), 'beforeafter')
+        self.assertEqual(list(e.iter()), [e, comment])
+        self.assertEqual(list(e.iter('root')), [e])
+        self.assertEqual(''.join(comment.itertext()), '')
+        self.assertEqual(list(comment.iter()), [comment])
+
+    def test_processinginstruction(self):
+        e = ET.Element('root')
+        e.text = 'before'
+        pi = ET.PI('test', 'instruction')
+        self.assertEqual(pi.text, 'test instruction')
+        pi.tail = 'after'
+        e.append(pi)
+        self.assertEqual(''.join(e.itertext()), 'beforeafter')
+        self.assertEqual(list(e.iter()), [e, pi])
+        self.assertEqual(list(e.iter('root')), [e])
+        self.assertEqual(''.join(pi.itertext()), '')
+        self.assertEqual(list(pi.iter()), [pi])
+
     def test_corners(self):
         # single root, no subelements
         a = ET.Element('a')

Lib/test/test_zipfile/test_core.py

@@ -3640,29 +3640,23 @@ def test_read_with_unsuitable_metadata_encoding(self):
 
     def test_read_after_append(self):
         newname = '\u56db'  # Han 'four'
-        expected_names = [name.encode('shift_jis').decode('cp437')
-                          for name in self.file_names[:2]] + self.file_names[2:]
-        expected_names.append(newname)
-        expected_content = (*self.file_content, b"newcontent")
+        newname2 = 'fünf'  # representable in cp437, but still stored as UTF-8
+        expected_names = [*self.file_names, newname, newname2]
+        mojibake_expected_names = [name.encode('shift_jis').decode('cp437')
+                                   if i < 2 else name
+                                   for i, name in enumerate(expected_names)]
+        expected_content = (*self.file_content, b"newcontent", b"newcontent2")
 
         with zipfile.ZipFile(TESTFN, "a") as zipfp:
             zipfp.writestr(newname, "newcontent")
-            self.assertEqual(sorted(zipfp.namelist()), sorted(expected_names))
+            zipfp.writestr(newname2, "newcontent2")
+            self.assertEqual(sorted(zipfp.namelist()), sorted(mojibake_expected_names))
 
         with zipfile.ZipFile(TESTFN, "r") as zipfp:
-            self._test_read(zipfp, expected_names, expected_content)
+            self._test_read(zipfp, mojibake_expected_names, expected_content)
 
         with zipfile.ZipFile(TESTFN, "r", metadata_encoding='shift_jis') as zipfp:
-            self.assertEqual(sorted(zipfp.namelist()), sorted(expected_names))
-            for i, (name, content) in enumerate(zip(expected_names, expected_content)):
-                info = zipfp.getinfo(name)
-                self.assertEqual(info.filename, name)
-                self.assertEqual(info.file_size, len(content))
-                if i < 2:
-                    with self.assertRaises(zipfile.BadZipFile):
-                        zipfp.read(name)
-                else:
-                    self.assertEqual(zipfp.read(name), content)
+            self._test_read(zipfp, expected_names, expected_content)
 
     def test_write_with_metadata_encoding(self):
         ZF = zipfile.ZipFile
@@ -3671,6 +3665,20 @@ def test_write_with_metadata_encoding(self):
                                         "^metadata_encoding is only"):
                 ZF("nonesuch.zip", mode, metadata_encoding="shift_jis")
 
+    def test_add_comment(self):
+        with zipfile.ZipFile(TESTFN, "r") as zipfp:
+            mojibake_expected_names = zipfp.namelist()
+
+        with zipfile.ZipFile(TESTFN, "a") as zipfp:
+            zipfp.comment = b'comment'
+            self.assertEqual(zipfp.namelist(), mojibake_expected_names)
+
+        with zipfile.ZipFile(TESTFN, "r") as zipfp:
+            self._test_read(zipfp, mojibake_expected_names, self.file_content)
+
+        with zipfile.ZipFile(TESTFN, "r", metadata_encoding='shift_jis') as zipfp:
+            self._test_read(zipfp, self.file_names, self.file_content)
+
     def test_cli_with_metadata_encoding(self):
         errmsg = "Non-conforming encodings not supported with -c."
         args = ["--metadata-encoding=shift_jis", "-c", "nonesuch", "nonesuch"]