# Source code for nose2.plugins.mp

    import logging
    import multiprocessing
    import multiprocessing.connection as connection
    import os
    import select
    import sys
    import unittest
    from collections.abc import Sequence

    from nose2 import events, loader, result, runner, session, util

    log = logging.getLogger(__name__)

    # Python 3.14: Change in multiprocessing API
    # https://docs.python.org/3/library/multiprocessing.html
    # #multiprocessing-start-methods
    # On POSIX platforms the default start method was changed from fork to
    # forkserver to retain the performance but avoid common multithreaded
    # process incompatibilities.
    # [...]
    # set_start_method() should not be used more than once in the program.
    multiprocessing.set_start_method("fork")

    class MultiProcess(events.Plugin):
        configSection = "multiprocess"

        def __init__(self):
            self.addArgument(
                self.setProcs,
                "N",
                "processes",
                "Number of processes used to run tests (0 = auto)",
            )
            self.testRunTimeout = self.config.as_float("test-run-timeout", 60.0)
            self._procs = self.config.as_int("processes", 0)
            self.setAddress(self.config.as_str("bind_address", None))

            self.cases = {}

        @property
        def procs(self):
            """Get the appropriate number of procs for self.procs if self._procs is
            0."""

            if self._procs == 0:
                try:
                    self._procs = multiprocessing.cpu_count()
                except NotImplementedError:
                    self._procs = 1
            return self._procs

        @procs.setter
        def procs(self, value):
            """Setter for procs property"""
            if value < 0:
                raise ValueError("Number of processes cannot be less than 0")
            self._procs = value

        def setProcs(self, num):
            self.procs = int(num[0])  # FIXME merge n fix
            self.register()

        def setAddress(self, address):
            if address is None or address.strip() == "":
                address = []
            else:
                address = [x.strip() for x in address.split(":")[:2]]

            # Background:  On Windows, select.select only works on sockets.  So the
            # ability to select a bindable address and optionally port for the mp
            # plugin was added.  Pipes should support a form of select, but this
            # would require using pywin32.  There are alternatives but all have
            # some kind of downside.  An alternative might be creating a connection
            # like object using a shared queue for incomings events.
            self.bind_host = None
            self.bind_port = 0

            if sys.platform == "win32" or address:
                self.bind_host = "127.116.157.163"
                if address and address[0]:
                    self.bind_host = address[0]

                self.bind_port = 0
                if len(address) >= 2:
                    self.bind_port = int(address[1])

        def pluginsLoaded(self, event):
            self.addMethods("registerInSubprocess", "startSubprocess", "stopSubprocess")

        def startTestRun(self, event):
            event.executeTests = self._runmp

        def beforeInteraction(self, event):
            # prevent interactive plugins from running
            event.handled = True
            return False

        def _runmp(self, test, result):
            # flatten technically modifies a hash of test cases, let's
            # only run it once per run.
            flat = list(self._flatten(test))

            # do not send import failures to the subprocesses, which will mangle them
            # but 'run' them in the main process.
            failed_import_id = "nose2.loader.LoadTestsFailure"
            result_ = self.session.testResult
            for testid in flat:
                if testid.startswith(failed_import_id):
                    self.cases[testid].run(result_)

            # XXX Process-Handling: The length of the filtered list needs to be
            # known for _startProcs, until this can be cleaned up.  This
            # wasn't the best way to deal with too few tests
            flat = [x for x in flat if not x.startswith(failed_import_id)]
            procs = self._startProcs(len(flat))

            # send one initial task to each process
            for _proc, conn in procs:
                if not flat:
                    break
                caseid = flat.pop(0)
                # NOTE: it throws errors on broken pipes and bad serialization
                conn.send(caseid)

            rdrs = [conn for proc, conn in procs if proc.is_alive()]
            while flat or rdrs:
                ready, _, _ = select.select(rdrs, [], [], self.testRunTimeout)
                for conn in ready:
                    # XXX Process-Handling: If we get an EOFError on receive the
                    # process finished= or we lost the process and the test it was
                    # working on.  Also do we rebuild the process?
                    try:
                        remote_events = conn.recv()
                    except EOFError:
                        # probably dead/12
                        log.warning("Subprocess connection closed unexpectedly")
                        continue

                    # If remote_events is None, the process exited normally,
                    # which should mean that we didn't any more tests for it.
                    if remote_events is None:
                        log.debug("Conn closed %s", conn)
                        rdrs.remove(conn)
                        continue

                    # replay events
                    testid, events = remote_events
                    log.debug("Received results for %s", testid)
                    for hook, event in events:
                        log.debug("Received %s(%s)", hook, event)
                        self._localize(event)
                        getattr(self.session.hooks, hook)(event)

                    # Send the next test_id
                    # NOTE: send throws errors on broken pipes and bad serialization
                    if not flat:
                        # If there are no more, send None - it's the 'done' flag
                        conn.send(None)
                        continue
                    caseid = flat.pop(0)
                    conn.send(caseid)

            for _, conn in procs:
                conn.close()

            # ensure we wait until all processes are done before
            # exiting, to allow plugins running there to finalize
            for proc, _ in procs:
                proc.join()

        def _prepConns(self):
            """
            If the ``bind_host`` is not ``None``, return:
                (multiprocessing.connection.Listener, (address, port, authkey))
            else:
                (parent_connection, child_connection)

            For the former case: ``accept`` must be called on the listener. In order
            to get a ``Connection`` object for the socket.
            """
            if self.bind_host is not None:
                # prevent "accidental" wire crossing
                authkey = os.urandom(20)
                address = (self.bind_host, self.bind_port)
                listener = connection.Listener(address, authkey=authkey)
                return (listener, listener.address + (authkey,))
            else:
                return multiprocessing.Pipe()

        def _acceptConns(self, parent_conn):
            """
            When listener is is a :class:`connection.Listener` instance: accept the next
            incoming connection.  However, a timeout mechanism is needed.  Since
            this functionality was added to support mp over inet sockets, this method
            assumes a Socket-based listen, and will accept the private _socket
            member to get a low_level socket to do a select on.
            """
            if isinstance(parent_conn, connection.Listener):
                # ick private interface
                rdrs = [parent_conn._listener._socket]
                readable, _, _ = select.select(rdrs, [], [], self.testRunTimeout)
                if readable:
                    return parent_conn.accept()
                else:
                    raise RuntimeError("MP: Socket Connection Failed")
            else:
                return parent_conn

        def _startProcs(self, test_count):
            # Create session export
            session_export = self._exportSession()
            procs = []
            count = min(test_count, self.procs)
            log.debug("Creating %i worker processes", count)
            for _ in range(0, count):
                parent_conn, child_conn = self._prepConns()
                proc = multiprocessing.Process(
                    target=procserver, args=(session_export, child_conn)
                )
                proc.daemon = True
                proc.start()
                parent_conn = self._acceptConns(parent_conn)
                procs.append((proc, parent_conn))
            return procs

        def _flatten(self, suite):
            """
            Flatten test-suite into list of IDs, AND record all test case
            into self.cases

            CAVEAT:  Due to current limitation of the MP plugin, examine the suite
                     tests to find out if they have class or module fixtures and
                     group them that way into name of test classes or module.
                     This is aid in their dispatch.
            """
            log.debug("Flattening test into list of IDs")
            mods = {}
            classes = {}
            stack = [suite]
            while stack:
                suite = stack.pop()
                for test in suite:
                    if isinstance(test, unittest.TestSuite):
                        stack.append(test)
                    else:
                        testid = util.test_name(test)
                        self.cases[testid] = test
                        if util.has_module_fixtures(test):
                            mods.setdefault(test.__class__.__module__, []).append(testid)
                        elif util.has_class_fixtures(test):
                            # testclasses support
                            if test.__class__.__name__ == "_MethodTestCase":
                                test = test.obj
                            classes.setdefault(
                                "%s.%s"
                                % (test.__class__.__module__, test.__class__.__name__),
                                [],
                            ).append(testid)
                        else:
                            yield testid

            yield from sorted(classes.keys())
            yield from sorted(mods.keys())

        def _localize(self, event):
            # XXX set loader, case, result etc to local ones, if present in event
            # (event case will be just the id)
            # (traceback in exc_info if any won't be real!)
            if hasattr(event, "result"):
                event.result = self.session.testResult
            if hasattr(event, "loader"):
                event.loader = self.session.testLoader
            if hasattr(event, "runner"):
                event.runner = self.session.testRunner
            if hasattr(event, "test") and isinstance(event.test, str):
                # remote event.case is the test id
                try:
                    event.test = self.cases[event.test]
                except KeyError:
                    # this happens when _flatten augments the test suite
                    # due to a class or module fixture being present
                    event.test = self.session.testLoader.loadTestsFromName(
                        event.test
                    )._tests[0]
                # subtest support
                if "subtest" in event.metadata:
                    message, params = event.metadata.pop("subtest")
                    # XXX the sentinel value does not survive the pickle
                    # round-trip and must be reset by hand
                    if type(message) == type(object()):  # noqa: E721
                        message = unittest.case._subtest_msg_sentinel
                    event.test = unittest.case._SubTest(event.test, message, params)

        def _exportSession(self):
            """
            Generate the session information passed to work process.

            CAVEAT: The entire contents of which *MUST* be pickleable
            and safe to use in the subprocess.

            This probably includes:
            * No argparse namespaces/named-tuples
            * No plugin instances
            * No hokes
            :return:
            """
            export = {
                "config": self.session.config,
                "verbosity": self.session.verbosity,
                "startDir": self.session.startDir,
                "topLevelDir": self.session.topLevelDir,
                "logLevel": self.session.logLevel,
                "pluginClasses": [],
            }
            event = RegisterInSubprocessEvent()
            # fire registerInSubprocess on plugins -- add those plugin classes
            # CAVEAT: classes must be pickleable!
            self.session.hooks.registerInSubprocess(event)
            export["pluginClasses"].extend(event.pluginClasses)
            return export

    def procserver(session_export, conn):
        # init logging system
        rlog = multiprocessing.log_to_stderr()
        rlog.setLevel(session_export["logLevel"])

        # make a real session from the "session" we got
        ssn = import_session(rlog, session_export)

        if isinstance(conn, Sequence):
            conn = connection.Client(conn[:2], authkey=conn[2])

        event = SubprocessEvent(
            ssn.testLoader, ssn.testResult, ssn.testRunner, ssn.plugins, conn
        )
        res = ssn.hooks.startSubprocess(event)
        if event.handled and not res:
            conn.send(None)
            conn.close()
            ssn.hooks.stopSubprocess(event)
            return
        # receive and run tests
        executor = event.executeTests
        for testid in gentests(conn):
            if testid is None:
                break
            # XXX to handle weird cases like layers, need to
            # deal with the case that testid is something other
            # than a simple string.
            test = event.loader.loadTestsFromName(testid)
            # XXX If there a need to protect the loop? try/except?
            rlog.debug("Execute test %s (%s)", testid, test)
            executor(test, event.result)
            events = list(ssn.hooks.flush())
            try:
                conn.send((testid, events))
                rlog.debug("Log for %s returned", testid)
            except Exception:
                rlog.exception(f"Fail sending event {testid}: {events}")
                # Send empty event list to unblock the conn.recv on main process.
                conn.send((testid, []))
        conn.send(None)
        conn.close()
        ssn.hooks.stopSubprocess(event)

    def import_session(rlog, session_export):
        ssn = session.Session()
        ssn.config = session_export["config"]
        ssn.hooks = RecordingPluginInterface()
        ssn.verbosity = session_export["verbosity"]
        ssn.startDir = session_export["startDir"]
        ssn.topLevelDir = session_export["topLevelDir"]
        ssn.prepareSysPath()
        loader_ = loader.PluggableTestLoader(ssn)
        ssn.testLoader = loader_
        result_ = result.PluggableTestResult(ssn)
        ssn.testResult = result_
        runner_ = runner.PluggableTestRunner(ssn)  # needed??
        ssn.testRunner = runner_
        # load and register plugins, forcing multiprocess to the end
        ssn.plugins = [
            plugin(session=ssn)
            for plugin in session_export["pluginClasses"]
            if plugin is not MultiProcess
        ]
        rlog.debug("Plugins loaded: %s", ssn.plugins)

        for plugin in ssn.plugins:
            plugin.register()
            rlog.debug("Registered %s in subprocess", plugin)

        # instantiating the plugin will register it.
        ssn.plugins.append(MultiProcess(session=ssn))
        rlog.debug("Registered %s in subprocess", MultiProcess)
        ssn.plugins[-1].pluginsLoaded(events.PluginsLoadedEvent(ssn.plugins))
        return ssn

    # test generator
    def gentests(conn):
        while True:
            try:
                testid = conn.recv()
                if testid is None:
                    return
                yield testid
            except EOFError:
                return

    # custom event classes

    class SubprocessEvent(events.Event):
        """Event fired at start and end of subprocess execution.

        .. attribute :: loader

           Test loader instance

        .. attribute :: result

           Test result

        .. attribute :: plugins

           List of plugins loaded in the subprocess.

        .. attribute :: connection

           The :class:`multiprocessing.Connection` instance that the
           subprocess uses for communication with the main process.

        .. attribute :: executeTests

           Callable that will be used to execute tests.  Plugins may set
           this attribute to wrap or otherwise change test execution. The
           callable must match the signature::

             def execute(suite, result):
                 ...

        """

        def __init__(self, loader, result, runner, plugins, connection, **metadata):
            self.loader = loader
            self.result = result
            self.runner = runner
            self.plugins = plugins
            self.connection = connection
            self.executeTests = lambda test, result: test(result)
            super().__init__(**metadata)

    class RegisterInSubprocessEvent(events.Event):
        """Event fired to notify plugins that multiprocess testing will occur

        .. attribute :: pluginClasses

           Add a plugin class to this list to cause the plugin to be
           instantiated in each test-running subprocess. The most common
           thing to do, for plugins that need to run in subprocesses, is::

             def registerInSubprocess(self, event):
                 event.pluginClasses.append(self.__class__)

        """

        def __init__(self, **metadata):
            self.pluginClasses = []
            super().__init__(**metadata)

    # custom hook system that records calls and events
    class RecordingHook(events.Hook):
        def __init__(self, method, interface):
            super().__init__(method)
            self.interface = interface

        def __call__(self, event):
            res = super().__call__(event)
            self.interface.log(self.method, event)
            return res

    class RecordingPluginInterface(events.PluginInterface):
        hookClass = RecordingHook
        noLogMethods = {
            "getTestCaseNames",
            "startSubprocess",
            "stopSubprocess",
            "registerInSubprocess",
            "moduleLoadedSuite",
            "getTestMethodNames",
        }

        def __init__(self):
            super().__init__()
            self.events = []

        def log(self, method, event):
            self.events.append((method, event))

        def flush(self):
            events = self.events[:]
            self.events = []
            return events

        def register(self, method, plugin):
            """Register a plugin for a method.

            :param method: A method name
            :param plugin: A plugin instance

            """
            self._hookForMethod(method).append(plugin)

        def __getattr__(self, attr):
            if attr.startswith("__"):
                raise AttributeError(f"No {attr} in {self}")
            return self._hookForMethod(attr)

        def _hookForMethod(self, method):
            # return recording hook for most hooks, normal hook for those
            # (like test loading and subprocess events) that we don't want
            # to send back to the main process.
            try:
                return self.hooks[method]
            except KeyError:
                if method in self.noLogMethods or method.startswith("loadTest"):
                    hook = events.Hook(method)
                else:
                    hook = self.hookClass(method, self)
            self.hooks[method] = hook
            return hook