gh-115122: Add --bisect option to regrtest (#115123)

* test.bisect_cmd now exit with code 0 on success, and code 1 on
  failure. Before, it was the opposite.
* test.bisect_cmd now runs the test worker process with
  -X faulthandler.
* regrtest RunTests: Add create_python_cmd() and bisect_cmd()
  methods.

Lib/test/test_regrtest.py

@@ -399,7 +399,7 @@ class ParseArgsTestCase(unittest.TestCase):
         self.checkError(['--unknown-option'],
                         'unrecognized arguments: --unknown-option')
 
-    def check_ci_mode(self, args, use_resources, rerun=True):
+    def create_regrtest(self, args):
         ns = cmdline._parse_args(args)
 
         # Check Regrtest attributes which are more reliable than Namespace
@@ -411,6 +411,10 @@ class ParseArgsTestCase(unittest.TestCase):
 
             regrtest = main.Regrtest(ns)
 
+        return regrtest
+
+    def check_ci_mode(self, args, use_resources, rerun=True):
+        regrtest = self.create_regrtest(args)
         self.assertEqual(regrtest.num_workers, -1)
         self.assertEqual(regrtest.want_rerun, rerun)
         self.assertTrue(regrtest.randomize)
@@ -455,6 +459,11 @@ class ParseArgsTestCase(unittest.TestCase):
         ns = cmdline._parse_args(args)
         self.assertFalse(ns._add_python_opts)
 
+    def test_bisect(self):
+        args = ['--bisect']
+        regrtest = self.create_regrtest(args)
+        self.assertTrue(regrtest.want_bisect)
+
 
 @dataclasses.dataclass(slots=True)
 class Rerun:
@@ -1192,6 +1201,47 @@ class ArgsTestCase(BaseTestCase):
     def test_huntrleaks_mp(self):
         self.check_huntrleaks(run_workers=True)
 
+    @unittest.skipUnless(support.Py_DEBUG, 'need a debug build')
+    def test_huntrleaks_bisect(self):
+        # test --huntrleaks --bisect
+        code = textwrap.dedent("""
+            import unittest
+
+            GLOBAL_LIST = []
+
+            class RefLeakTest(unittest.TestCase):
+                def test1(self):
+                    pass
+
+                def test2(self):
+                    pass
+
+                def test3(self):
+                    GLOBAL_LIST.append(object())
+
+                def test4(self):
+                    pass
+        """)
+
+        test = self.create_test('huntrleaks', code=code)
+
+        filename = 'reflog.txt'
+        self.addCleanup(os_helper.unlink, filename)
+        cmd = ['--huntrleaks', '3:3:', '--bisect', test]
+        output = self.run_tests(*cmd,
+                                exitcode=EXITCODE_BAD_TEST,
+                                stderr=subprocess.STDOUT)
+
+        self.assertIn(f"Bisect {test}", output)
+        self.assertIn(f"Bisect {test}: exit code 0", output)
+
+        # test3 is the one which leaks
+        self.assertIn("Bisection completed in", output)
+        self.assertIn(
+            "Tests (1):\n"
+            f"* {test}.RefLeakTest.test3\n",
+            output)
+
     @unittest.skipUnless(support.Py_DEBUG, 'need a debug build')
     def test_huntrleaks_fd_leak(self):
         # test --huntrleaks for file descriptor leak