gh-109162: Refactor libregrtest WorkerJob (#109171)

* Rename --worker-args command line option to --worker-json.
* Rename _parse_worker_args() to _parse_worker_json().
* WorkerJob:

  * Add runtests attribute
  * Remove test_name and rerun attribute

* Rename run_test_in_subprocess() to create_worker_process().
* Rename run_tests_worker() to worker_process().
* create_worker_process() uses json.dump(): write directly JSON to
  stdout.
* Convert MultiprocessResult to a frozen dataclass.
* Rename RunTests.match_tests to RunTests.match_tests_dict.

5 files changed, 48 insertions, 41 deletions

diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index bbac980..c08b3be 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -170,6 +170,7 @@ class Namespace(argparse.Namespace):
         self.ignore_tests = None
         self.pgo = False
         self.pgo_extended = False
+        self.worker_json = None
 
         super().__init__(**kwargs)
 
@@ -205,7 +206,7 @@ def _create_parser():
     group.add_argument('--wait', action='store_true',
                        help='wait for user input, e.g., allow a debugger '
                             'to be attached')
-    group.add_argument('--worker-args', metavar='ARGS')
+    group.add_argument('--worker-json', metavar='ARGS')
     group.add_argument('-S', '--start', metavar='START',
                        help='the name of the test at which to start.' +
                             more_details)
diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index 13500fa..cd053c5 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -336,7 +336,7 @@ class Regrtest:
 
         # Get tests to re-run
         tests = [result.test_name for result in need_rerun]
-        match_tests = self.get_rerun_match(need_rerun)
+        match_tests_dict = self.get_rerun_match(need_rerun)
 
         # Clear previously failed tests
         self.rerun_bad.extend(self.bad)
@@ -346,7 +346,7 @@ class Regrtest:
         # Re-run failed tests
         self.log(f"Re-running {len(tests)} failed tests in verbose mode in subprocesses")
         runtests = runtests.copy(tests=tuple(tests),
-                                 match_tests=match_tests,
+                                 match_tests_dict=match_tests_dict,
                                  rerun=True,
                                  forever=False)
         self.set_tests(runtests)
@@ -742,7 +742,7 @@ class Regrtest:
         self.tmp_dir = os.path.abspath(self.tmp_dir)
 
     def is_worker(self):
-        return (self.ns.worker_args is not None)
+        return (self.ns.worker_json is not None)
 
     def create_temp_dir(self):
         os.makedirs(self.tmp_dir, exist_ok=True)
@@ -870,8 +870,8 @@ class Regrtest:
 
     def _main(self):
         if self.is_worker():
-            from test.libregrtest.runtest_mp import run_tests_worker
-            run_tests_worker(self.ns.worker_args)
+            from test.libregrtest.runtest_mp import worker_process
+            worker_process(self.ns.worker_json)
             return
 
         if self.want_wait:
diff --git a/Lib/test/libregrtest/runtest.py b/Lib/test/libregrtest/runtest.py
index 5fcbb77..ea5d056 100644
--- a/Lib/test/libregrtest/runtest.py
+++ b/Lib/test/libregrtest/runtest.py
@@ -208,7 +208,7 @@ class TestResult:
 @dataclasses.dataclass(slots=True, frozen=True)
 class RunTests:
     tests: TestTuple
-    match_tests: FilterDict | None = None
+    match_tests_dict: FilterDict | None = None
     rerun: bool = False
     forever: bool = False
 
@@ -218,8 +218,8 @@ class RunTests:
         return RunTests(**state)
 
     def get_match_tests(self, test_name) -> FilterTuple | None:
-        if self.match_tests is not None:
-            return self.match_tests.get(test_name, None)
+        if self.match_tests_dict is not None:
+            return self.match_tests_dict.get(test_name, None)
         else:
             return None
 
diff --git a/Lib/test/libregrtest/runtest_mp.py b/Lib/test/libregrtest/runtest_mp.py
index 2ecdfca..45db24f 100644
--- a/Lib/test/libregrtest/runtest_mp.py
+++ b/Lib/test/libregrtest/runtest_mp.py
@@ -46,9 +46,8 @@ USE_PROCESS_GROUP = (hasattr(os, "setsid") and hasattr(os, "killpg"))
 
 @dataclasses.dataclass(slots=True)
 class WorkerJob:
-    test_name: str
+    runtests: RunTests
     namespace: Namespace
-    rerun: bool = False
     match_tests: FilterTuple | None = None
 
 
@@ -70,6 +69,7 @@ class _EncodeWorkerJob(json.JSONEncoder):
 def _decode_worker_job(d: dict[str, Any]) -> WorkerJob | dict[str, Any]:
     if "__worker_job__" in d:
         d.pop('__worker_job__')
+        d['runtests'] = RunTests(**d['runtests'])
         return WorkerJob(**d)
     if "__namespace__" in d:
         d.pop('__namespace__')
@@ -78,17 +78,16 @@ def _decode_worker_job(d: dict[str, Any]) -> WorkerJob | dict[str, Any]:
         return d
 
 
-def _parse_worker_args(worker_json: str) -> tuple[Namespace, str]:
-    return json.loads(worker_json,
-                      object_hook=_decode_worker_job)
+def _parse_worker_json(worker_json: str) -> tuple[Namespace, str]:
+    return json.loads(worker_json, object_hook=_decode_worker_job)
 
 
-def run_test_in_subprocess(worker_job: WorkerJob,
-                           output_file: TextIO,
-                           tmp_dir: str | None = None) -> subprocess.Popen:
+def create_worker_process(worker_job: WorkerJob,
+                          output_file: TextIO,
+                          tmp_dir: str | None = None) -> subprocess.Popen:
     ns = worker_job.namespace
     python = ns.python
-    worker_args = json.dumps(worker_job, cls=_EncodeWorkerJob)
+    worker_json = json.dumps(worker_job, cls=_EncodeWorkerJob)
 
     if python is not None:
         executable = python
@@ -97,7 +96,7 @@ def run_test_in_subprocess(worker_job: WorkerJob,
     cmd = [*executable, *support.args_from_interpreter_flags(),
            '-u',    # Unbuffered stdout and stderr
            '-m', 'test.regrtest',
-           '--worker-args', worker_args]
+           '--worker-json', worker_json]
 
     env = dict(os.environ)
     if tmp_dir is not None:
@@ -122,16 +121,16 @@ def run_test_in_subprocess(worker_job: WorkerJob,
     return subprocess.Popen(cmd, **kw)
 
 
-def run_tests_worker(worker_json: str) -> NoReturn:
-    worker_job = _parse_worker_args(worker_json)
+def worker_process(worker_json: str) -> NoReturn:
+    worker_job = _parse_worker_json(worker_json)
+    runtests = worker_job.runtests
     ns = worker_job.namespace
-    test_name = worker_job.test_name
-    rerun = worker_job.rerun
-    match_tests = worker_job.match_tests
+    test_name = runtests.tests[0]
+    match_tests: FilterTuple | None = worker_job.match_tests
 
     setup_tests(ns)
 
-    if rerun:
+    if runtests.rerun:
         if match_tests:
             matching = "matching: " + ", ".join(match_tests)
             print(f"Re-running {test_name} in verbose mode ({matching})", flush=True)
@@ -139,14 +138,15 @@ def run_tests_worker(worker_json: str) -> NoReturn:
             print(f"Re-running {test_name} in verbose mode", flush=True)
         ns.verbose = True
 
-    if match_tests is not None:
-        ns.match_tests = match_tests
+        if match_tests is not None:
+            ns.match_tests = match_tests
 
     result = runtest(ns, test_name)
     print()   # Force a newline (just in case)
 
     # Serialize TestResult as dict in JSON
-    print(json.dumps(result, cls=EncodeTestResult), flush=True)
+    json.dump(result, sys.stdout, cls=EncodeTestResult)
+    sys.stdout.flush()
     sys.exit(0)
 
 
@@ -173,7 +173,8 @@ class MultiprocessIterator:
             self.tests_iter = None
 
 
-class MultiprocessResult(NamedTuple):
+@dataclasses.dataclass(slots=True, frozen=True)
+class MultiprocessResult:
     result: TestResult
     # bpo-45410: stderr is written into stdout to keep messages order
     worker_stdout: str | None = None
@@ -198,7 +199,6 @@ class TestWorkerProcess(threading.Thread):
         self.ns = runner.ns
         self.timeout = runner.worker_timeout
         self.regrtest = runner.regrtest
-        self.rerun = runner.rerun
         self.current_test_name = None
         self.start_time = None
         self._popen = None
@@ -264,9 +264,8 @@ class TestWorkerProcess(threading.Thread):
 
     def _run_process(self, worker_job, output_file: TextIO,
                      tmp_dir: str | None = None) -> int:
-        self.current_test_name = worker_job.test_name
         try:
-            popen = run_test_in_subprocess(worker_job, output_file, tmp_dir)
+            popen = create_worker_process(worker_job, output_file, tmp_dir)
 
             self._killed = False
             self._popen = popen
@@ -316,6 +315,8 @@ class TestWorkerProcess(threading.Thread):
             self.current_test_name = None
 
     def _runtest(self, test_name: str) -> MultiprocessResult:
+        self.current_test_name = test_name
+
         if sys.platform == 'win32':
             # gh-95027: When stdout is not a TTY, Python uses the ANSI code
             # page for the sys.stdout encoding. If the main process runs in a
@@ -324,15 +325,20 @@ class TestWorkerProcess(threading.Thread):
         else:
             encoding = sys.stdout.encoding
 
-        match_tests = self.runtests.get_match_tests(test_name)
+        tests = (test_name,)
+        if self.runtests.rerun:
+            match_tests = self.runtests.get_match_tests(test_name)
+        else:
+            match_tests = None
+        worker_runtests = self.runtests.copy(tests=tests)
+        worker_job = WorkerJob(
+            worker_runtests,
+            namespace=self.ns,
+            match_tests=match_tests)
 
         # gh-94026: Write stdout+stderr to a tempfile as workaround for
         # non-blocking pipes on Emscripten with NodeJS.
         with tempfile.TemporaryFile('w+', encoding=encoding) as stdout_file:
-            worker_job = WorkerJob(test_name,
-                                   namespace=self.ns,
-                                   rerun=self.rerun,
-                                   match_tests=match_tests)
             # gh-93353: Check for leaked temporary files in the parent process,
             # since the deletion of temporary files can happen late during
             # Python finalization: too late for libregrtest.
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index ece8c1f..8cced1f 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -75,10 +75,10 @@ class ParseArgsTestCase(unittest.TestCase):
         ns = libregrtest._parse_args(['--wait'])
         self.assertTrue(ns.wait)
 
-    def test_worker_args(self):
-        ns = libregrtest._parse_args(['--worker-args', '[[], {}]'])
-        self.assertEqual(ns.worker_args, '[[], {}]')
-        self.checkError(['--worker-args'], 'expected one argument')
+    def test_worker_json(self):
+        ns = libregrtest._parse_args(['--worker-json', '[[], {}]'])
+        self.assertEqual(ns.worker_json, '[[], {}]')
+        self.checkError(['--worker-json'], 'expected one argument')
 
     def test_start(self):
         for opt in '-S', '--start':