thirdparty: remove Python 2-specific selectors2 copy

The selectors module was added in Python 3.4. Because we require Python 3.6, it
will always be available. Therefore the selectors2 module is not imported.

I’ve verified that the selectors2-specific workaround in commandserver.py is not
necessary with the selectors module from the standard library. It returns an
empty list if timeout was exceeded.

The pytype directive was needed to silence the following error:

File "/tmp/mercurial-ci/mercurial/worker.py", line 299, in _posixworker: No attribute 'close' on int [attribute-error]
  In Union[_typeshed.HasFileno, int]
File "/tmp/mercurial-ci/mercurial/worker.py", line 299, in _posixworker: No attribute 'close' on _typeshed.HasFileno [attribute-error]
  In Union[_typeshed.HasFileno, int]

mercurial/commandserver.py

@@ -1,770 +1,756 b''
 # commandserver.py - communicate with Mercurial's API over a pipe
 #
 #  Copyright Olivia Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 
 import errno
 import gc
 import os
 import random
+import selectors
 import signal
 import socket
 import struct
 import traceback
 
-try:
-    import selectors
-
-    selectors.BaseSelector
-except ImportError:
-    from .thirdparty import selectors2 as selectors
-
 from .i18n import _
 from .pycompat import getattr
 from . import (
     encoding,
     error,
     loggingutil,
     pycompat,
     repocache,
     util,
     vfs as vfsmod,
 )
 from .utils import (
     cborutil,
     procutil,
 )
 
 
 class channeledoutput:
     """
     Write data to out in the following format:
 
     data length (unsigned int),
     data
     """
 
     def __init__(self, out, channel):
         self.out = out
         self.channel = channel
 
     @property
     def name(self):
         return b'<%c-channel>' % self.channel
 
     def write(self, data):
         if not data:
             return
         # single write() to guarantee the same atomicity as the underlying file
         self.out.write(struct.pack(b'>cI', self.channel, len(data)) + data)
         self.out.flush()
 
     def __getattr__(self, attr):
         if attr in ('isatty', 'fileno', 'tell', 'seek'):
             raise AttributeError(attr)
         return getattr(self.out, attr)
 
 
 class channeledmessage:
     """
     Write encoded message and metadata to out in the following format:
 
     data length (unsigned int),
     encoded message and metadata, as a flat key-value dict.
 
     Each message should have 'type' attribute. Messages of unknown type
     should be ignored.
     """
 
     # teach ui that write() can take **opts
     structured = True
 
     def __init__(self, out, channel, encodename, encodefn):
         self._cout = channeledoutput(out, channel)
         self.encoding = encodename
         self._encodefn = encodefn
 
     def write(self, data, **opts):
         opts = pycompat.byteskwargs(opts)
         if data is not None:
             opts[b'data'] = data
         self._cout.write(self._encodefn(opts))
 
     def __getattr__(self, attr):
         return getattr(self._cout, attr)
 
 
 class channeledinput:
     """
     Read data from in_.
 
     Requests for input are written to out in the following format:
     channel identifier - 'I' for plain input, 'L' line based (1 byte)
     how many bytes to send at most (unsigned int),
 
     The client replies with:
     data length (unsigned int), 0 meaning EOF
     data
     """
 
     maxchunksize = 4 * 1024
 
     def __init__(self, in_, out, channel):
         self.in_ = in_
         self.out = out
         self.channel = channel
 
     @property
     def name(self):
         return b'<%c-channel>' % self.channel
 
     def read(self, size=-1):
         if size < 0:
             # if we need to consume all the clients input, ask for 4k chunks
             # so the pipe doesn't fill up risking a deadlock
             size = self.maxchunksize
             s = self._read(size, self.channel)
             buf = s
             while s:
                 s = self._read(size, self.channel)
                 buf += s
 
             return buf
         else:
             return self._read(size, self.channel)
 
     def _read(self, size, channel):
         if not size:
             return b''
         assert size > 0
 
         # tell the client we need at most size bytes
         self.out.write(struct.pack(b'>cI', channel, size))
         self.out.flush()
 
         length = self.in_.read(4)
         length = struct.unpack(b'>I', length)[0]
         if not length:
             return b''
         else:
             return self.in_.read(length)
 
     def readline(self, size=-1):
         if size < 0:
             size = self.maxchunksize
             s = self._read(size, b'L')
             buf = s
             # keep asking for more until there's either no more or
             # we got a full line
             while s and not s.endswith(b'\n'):
                 s = self._read(size, b'L')
                 buf += s
 
             return buf
         else:
             return self._read(size, b'L')
 
     def __iter__(self):
         return self
 
     def next(self):
         l = self.readline()
         if not l:
             raise StopIteration
         return l
 
     __next__ = next
 
     def __getattr__(self, attr):
         if attr in ('isatty', 'fileno', 'tell', 'seek'):
             raise AttributeError(attr)
         return getattr(self.in_, attr)
 
 
 _messageencoders = {
     b'cbor': lambda v: b''.join(cborutil.streamencode(v)),
 }
 
 
 def _selectmessageencoder(ui):
     encnames = ui.configlist(b'cmdserver', b'message-encodings')
     for n in encnames:
         f = _messageencoders.get(n)
         if f:
             return n, f
     raise error.Abort(
         b'no supported message encodings: %s' % b' '.join(encnames)
     )
 
 
 class server:
     """
     Listens for commands on fin, runs them and writes the output on a channel
     based stream to fout.
     """
 
     def __init__(self, ui, repo, fin, fout, prereposetups=None):
         self.cwd = encoding.getcwd()
 
         if repo:
             # the ui here is really the repo ui so take its baseui so we don't
             # end up with its local configuration
             self.ui = repo.baseui
             self.repo = repo
             self.repoui = repo.ui
         else:
             self.ui = ui
             self.repo = self.repoui = None
         self._prereposetups = prereposetups
 
         self.cdebug = channeledoutput(fout, b'd')
         self.cerr = channeledoutput(fout, b'e')
         self.cout = channeledoutput(fout, b'o')
         self.cin = channeledinput(fin, fout, b'I')
         self.cresult = channeledoutput(fout, b'r')
 
         if self.ui.config(b'cmdserver', b'log') == b'-':
             # switch log stream of server's ui to the 'd' (debug) channel
             # (don't touch repo.ui as its lifetime is longer than the server)
             self.ui = self.ui.copy()
             setuplogging(self.ui, repo=None, fp=self.cdebug)
 
         self.cmsg = None
         if ui.config(b'ui', b'message-output') == b'channel':
             encname, encfn = _selectmessageencoder(ui)
             self.cmsg = channeledmessage(fout, b'm', encname, encfn)
 
         self.client = fin
 
         # If shutdown-on-interrupt is off, the default SIGINT handler is
         # removed so that client-server communication wouldn't be interrupted.
         # For example, 'runcommand' handler will issue three short read()s.
         # If one of the first two read()s were interrupted, the communication
         # channel would be left at dirty state and the subsequent request
         # wouldn't be parsed. So catching KeyboardInterrupt isn't enough.
         self._shutdown_on_interrupt = ui.configbool(
             b'cmdserver', b'shutdown-on-interrupt'
         )
         self._old_inthandler = None
         if not self._shutdown_on_interrupt:
             self._old_inthandler = signal.signal(signal.SIGINT, signal.SIG_IGN)
 
     def cleanup(self):
         """release and restore resources taken during server session"""
         if not self._shutdown_on_interrupt:
             signal.signal(signal.SIGINT, self._old_inthandler)
 
     def _read(self, size):
         if not size:
             return b''
 
         data = self.client.read(size)
 
         # is the other end closed?
         if not data:
             raise EOFError
 
         return data
 
     def _readstr(self):
         """read a string from the channel
 
         format:
         data length (uint32), data
         """
         length = struct.unpack(b'>I', self._read(4))[0]
         if not length:
             return b''
         return self._read(length)
 
     def _readlist(self):
         """read a list of NULL separated strings from the channel"""
         s = self._readstr()
         if s:
             return s.split(b'\0')
         else:
             return []
 
     def _dispatchcommand(self, req):
         from . import dispatch  # avoid cycle
 
         if self._shutdown_on_interrupt:
             # no need to restore SIGINT handler as it is unmodified.
             return dispatch.dispatch(req)
 
         try:
             signal.signal(signal.SIGINT, self._old_inthandler)
             return dispatch.dispatch(req)
         except error.SignalInterrupt:
             # propagate SIGBREAK, SIGHUP, or SIGTERM.
             raise
         except KeyboardInterrupt:
             # SIGINT may be received out of the try-except block of dispatch(),
             # so catch it as last ditch. Another KeyboardInterrupt may be
             # raised while handling exceptions here, but there's no way to
             # avoid that except for doing everything in C.
             pass
         finally:
             signal.signal(signal.SIGINT, signal.SIG_IGN)
         # On KeyboardInterrupt, print error message and exit *after* SIGINT
         # handler removed.
         req.ui.error(_(b'interrupted!\n'))
         return -1
 
     def runcommand(self):
         """reads a list of \0 terminated arguments, executes
         and writes the return code to the result channel"""
         from . import dispatch  # avoid cycle
 
         args = self._readlist()
 
         # copy the uis so changes (e.g. --config or --verbose) don't
         # persist between requests
         copiedui = self.ui.copy()
         uis = [copiedui]
         if self.repo:
             self.repo.baseui = copiedui
             # clone ui without using ui.copy because this is protected
             repoui = self.repoui.__class__(self.repoui)
             repoui.copy = copiedui.copy  # redo copy protection
             uis.append(repoui)
             self.repo.ui = self.repo.dirstate._ui = repoui
             self.repo.invalidateall()
 
         for ui in uis:
             ui.resetstate()
             # any kind of interaction must use server channels, but chg may
             # replace channels by fully functional tty files. so nontty is
             # enforced only if cin is a channel.
             if not util.safehasattr(self.cin, b'fileno'):
                 ui.setconfig(b'ui', b'nontty', b'true', b'commandserver')
 
         req = dispatch.request(
             args[:],
             copiedui,
             self.repo,
             self.cin,
             self.cout,
             self.cerr,
             self.cmsg,
             prereposetups=self._prereposetups,
         )
 
         try:
             ret = self._dispatchcommand(req) & 255
             # If shutdown-on-interrupt is off, it's important to write the
             # result code *after* SIGINT handler removed. If the result code
             # were lost, the client wouldn't be able to continue processing.
             self.cresult.write(struct.pack(b'>i', int(ret)))
         finally:
             # restore old cwd
             if b'--cwd' in args:
                 os.chdir(self.cwd)
 
     def getencoding(self):
         """writes the current encoding to the result channel"""
         self.cresult.write(encoding.encoding)
 
     def serveone(self):
         cmd = self.client.readline()[:-1]
         if cmd:
             handler = self.capabilities.get(cmd)
             if handler:
                 handler(self)
             else:
                 # clients are expected to check what commands are supported by
                 # looking at the servers capabilities
                 raise error.Abort(_(b'unknown command %s') % cmd)
 
         return cmd != b''
 
     capabilities = {b'runcommand': runcommand, b'getencoding': getencoding}
 
     def serve(self):
         hellomsg = b'capabilities: ' + b' '.join(sorted(self.capabilities))
         hellomsg += b'\n'
         hellomsg += b'encoding: ' + encoding.encoding
         hellomsg += b'\n'
         if self.cmsg:
             hellomsg += b'message-encoding: %s\n' % self.cmsg.encoding
         hellomsg += b'pid: %d' % procutil.getpid()
         if util.safehasattr(os, b'getpgid'):
             hellomsg += b'\n'
             hellomsg += b'pgid: %d' % os.getpgid(0)
 
         # write the hello msg in -one- chunk
         self.cout.write(hellomsg)
 
         try:
             while self.serveone():
                 pass
         except EOFError:
             # we'll get here if the client disconnected while we were reading
             # its request
             return 1
 
         return 0
 
 
 def setuplogging(ui, repo=None, fp=None):
     """Set up server logging facility
 
     If cmdserver.log is '-', log messages will be sent to the given fp.
     It should be the 'd' channel while a client is connected, and otherwise
     is the stderr of the server process.
     """
     # developer config: cmdserver.log
     logpath = ui.config(b'cmdserver', b'log')
     if not logpath:
         return
     # developer config: cmdserver.track-log
     tracked = set(ui.configlist(b'cmdserver', b'track-log'))
 
     if logpath == b'-' and fp:
         logger = loggingutil.fileobjectlogger(fp, tracked)
     elif logpath == b'-':
         logger = loggingutil.fileobjectlogger(ui.ferr, tracked)
     else:
         logpath = util.abspath(util.expandpath(logpath))
         # developer config: cmdserver.max-log-files
         maxfiles = ui.configint(b'cmdserver', b'max-log-files')
         # developer config: cmdserver.max-log-size
         maxsize = ui.configbytes(b'cmdserver', b'max-log-size')
         vfs = vfsmod.vfs(os.path.dirname(logpath))
         logger = loggingutil.filelogger(
             vfs,
             os.path.basename(logpath),
             tracked,
             maxfiles=maxfiles,
             maxsize=maxsize,
         )
 
     targetuis = {ui}
     if repo:
         targetuis.add(repo.baseui)
         targetuis.add(repo.ui)
     for u in targetuis:
         u.setlogger(b'cmdserver', logger)
 
 
 class pipeservice:
     def __init__(self, ui, repo, opts):
         self.ui = ui
         self.repo = repo
 
     def init(self):
         pass
 
     def run(self):
         ui = self.ui
         # redirect stdio to null device so that broken extensions or in-process
         # hooks will never cause corruption of channel protocol.
         with ui.protectedfinout() as (fin, fout):
             sv = server(ui, self.repo, fin, fout)
             try:
                 return sv.serve()
             finally:
                 sv.cleanup()
 
 
 def _initworkerprocess():
     # use a different process group from the master process, in order to:
     # 1. make the current process group no longer "orphaned" (because the
     #    parent of this process is in a different process group while
     #    remains in a same session)
     #    according to POSIX 2.2.2.52, orphaned process group will ignore
     #    terminal-generated stop signals like SIGTSTP (Ctrl+Z), which will
     #    cause trouble for things like ncurses.
     # 2. the client can use kill(-pgid, sig) to simulate terminal-generated
     #    SIGINT (Ctrl+C) and process-exit-generated SIGHUP. our child
     #    processes like ssh will be killed properly, without affecting
     #    unrelated processes.
     os.setpgid(0, 0)
     # change random state otherwise forked request handlers would have a
     # same state inherited from parent.
     random.seed()
 
 
 def _serverequest(ui, repo, conn, createcmdserver, prereposetups):
     fin = conn.makefile('rb')
     fout = conn.makefile('wb')
     sv = None
     try:
         sv = createcmdserver(repo, conn, fin, fout, prereposetups)
         try:
             sv.serve()
         # handle exceptions that may be raised by command server. most of
         # known exceptions are caught by dispatch.
         except error.Abort as inst:
             ui.error(_(b'abort: %s\n') % inst.message)
         except IOError as inst:
             if inst.errno != errno.EPIPE:
                 raise
         except KeyboardInterrupt:
             pass
         finally:
             sv.cleanup()
     except:  # re-raises
         # also write traceback to error channel. otherwise client cannot
         # see it because it is written to server's stderr by default.
         if sv:
             cerr = sv.cerr
         else:
             cerr = channeledoutput(fout, b'e')
         cerr.write(encoding.strtolocal(traceback.format_exc()))
         raise
     finally:
         fin.close()
         try:
             fout.close()  # implicit flush() may cause another EPIPE
         except IOError as inst:
             if inst.errno != errno.EPIPE:
                 raise
 
 
 class unixservicehandler:
     """Set of pluggable operations for unix-mode services
 
     Almost all methods except for createcmdserver() are called in the main
     process. You can't pass mutable resource back from createcmdserver().
     """
 
     pollinterval = None
 
     def __init__(self, ui):
         self.ui = ui
 
     def bindsocket(self, sock, address):
         util.bindunixsocket(sock, address)
         sock.listen(socket.SOMAXCONN)
         self.ui.status(_(b'listening at %s\n') % address)
         self.ui.flush()  # avoid buffering of status message
 
     def unlinksocket(self, address):
         os.unlink(address)
 
     def shouldexit(self):
         """True if server should shut down; checked per pollinterval"""
         return False
 
     def newconnection(self):
         """Called when main process notices new connection"""
 
     def createcmdserver(self, repo, conn, fin, fout, prereposetups):
         """Create new command server instance; called in the process that
         serves for the current connection"""
         return server(self.ui, repo, fin, fout, prereposetups)
 
 
 class unixforkingservice:
     """
     Listens on unix domain socket and forks server per connection
     """
 
     def __init__(self, ui, repo, opts, handler=None):
         self.ui = ui
         self.repo = repo
         self.address = opts[b'address']
         if not util.safehasattr(socket, b'AF_UNIX'):
             raise error.Abort(_(b'unsupported platform'))
         if not self.address:
             raise error.Abort(_(b'no socket path specified with --address'))
         self._servicehandler = handler or unixservicehandler(ui)
         self._sock = None
         self._mainipc = None
         self._workeripc = None
         self._oldsigchldhandler = None
         self._workerpids = set()  # updated by signal handler; do not iterate
         self._socketunlinked = None
         # experimental config: cmdserver.max-repo-cache
         maxlen = ui.configint(b'cmdserver', b'max-repo-cache')
         if maxlen < 0:
             raise error.Abort(_(b'negative max-repo-cache size not allowed'))
         self._repoloader = repocache.repoloader(ui, maxlen)
         # attempt to avoid crash in CoreFoundation when using chg after fix in
         # a89381e04c58
         if pycompat.isdarwin:
             procutil.gui()
 
     def init(self):
         self._sock = socket.socket(socket.AF_UNIX)
         # IPC channel from many workers to one main process; this is actually
         # a uni-directional pipe, but is backed by a DGRAM socket so each
         # message can be easily separated.
         o = socket.socketpair(socket.AF_UNIX, socket.SOCK_DGRAM)
         self._mainipc, self._workeripc = o
         self._servicehandler.bindsocket(self._sock, self.address)
         if util.safehasattr(procutil, b'unblocksignal'):
             procutil.unblocksignal(signal.SIGCHLD)
         o = signal.signal(signal.SIGCHLD, self._sigchldhandler)
         self._oldsigchldhandler = o
         self._socketunlinked = False
         self._repoloader.start()
 
     def _unlinksocket(self):
         if not self._socketunlinked:
             self._servicehandler.unlinksocket(self.address)
             self._socketunlinked = True
 
     def _cleanup(self):
         signal.signal(signal.SIGCHLD, self._oldsigchldhandler)
         self._sock.close()
         self._mainipc.close()
         self._workeripc.close()
         self._unlinksocket()
         self._repoloader.stop()
         # don't kill child processes as they have active clients, just wait
         self._reapworkers(0)
 
     def run(self):
         try:
             self._mainloop()
         finally:
             self._cleanup()
 
     def _mainloop(self):
         exiting = False
         h = self._servicehandler
         selector = selectors.DefaultSelector()
         selector.register(
             self._sock, selectors.EVENT_READ, self._acceptnewconnection
         )
         selector.register(
             self._mainipc, selectors.EVENT_READ, self._handlemainipc
         )
         while True:
             if not exiting and h.shouldexit():
                 # clients can no longer connect() to the domain socket, so
                 # we stop queuing new requests.
                 # for requests that are queued (connect()-ed, but haven't been
                 # accept()-ed), handle them before exit. otherwise, clients
                 # waiting for recv() will receive ECONNRESET.
                 self._unlinksocket()
                 exiting = True
-            try:
                 events = selector.select(timeout=h.pollinterval)
-            except OSError as inst:
-                # selectors2 raises ETIMEDOUT if timeout exceeded while
-                # handling signal interrupt. That's probably wrong, but
-                # we can easily get around it.
-                if inst.errno != errno.ETIMEDOUT:
-                    raise
-                events = []
             if not events:
                 # only exit if we completed all queued requests
                 if exiting:
                     break
                 continue
             for key, _mask in events:
                 key.data(key.fileobj, selector)
         selector.close()
 
     def _acceptnewconnection(self, sock, selector):
         h = self._servicehandler
         try:
             conn, _addr = sock.accept()
         except socket.error as inst:
             if inst.args[0] == errno.EINTR:
                 return
             raise
 
         # Future improvement: On Python 3.7, maybe gc.freeze() can be used
         # to prevent COW memory from being touched by GC.
         # https://instagram-engineering.com/
         #   copy-on-write-friendly-python-garbage-collection-ad6ed5233ddf
         pid = os.fork()
         if pid:
             try:
                 self.ui.log(
                     b'cmdserver', b'forked worker process (pid=%d)\n', pid
                 )
                 self._workerpids.add(pid)
                 h.newconnection()
             finally:
                 conn.close()  # release handle in parent process
         else:
             try:
                 selector.close()
                 sock.close()
                 self._mainipc.close()
                 self._runworker(conn)
                 conn.close()
                 self._workeripc.close()
                 os._exit(0)
             except:  # never return, hence no re-raises
                 try:
                     self.ui.traceback(force=True)
                 finally:
                     os._exit(255)
 
     def _handlemainipc(self, sock, selector):
         """Process messages sent from a worker"""
         try:
             path = sock.recv(32768)  # large enough to receive path
         except socket.error as inst:
             if inst.args[0] == errno.EINTR:
                 return
             raise
         self._repoloader.load(path)
 
     def _sigchldhandler(self, signal, frame):
         self._reapworkers(os.WNOHANG)
 
     def _reapworkers(self, options):
         while self._workerpids:
             try:
                 pid, _status = os.waitpid(-1, options)
             except OSError as inst:
                 if inst.errno == errno.EINTR:
                     continue
                 if inst.errno != errno.ECHILD:
                     raise
                 # no child processes at all (reaped by other waitpid()?)
                 self._workerpids.clear()
                 return
             if pid == 0:
                 # no waitable child processes
                 return
             self.ui.log(b'cmdserver', b'worker process exited (pid=%d)\n', pid)
             self._workerpids.discard(pid)
 
     def _runworker(self, conn):
         signal.signal(signal.SIGCHLD, self._oldsigchldhandler)
         _initworkerprocess()
         h = self._servicehandler
         try:
             _serverequest(
                 self.ui,
                 self.repo,
                 conn,
                 h.createcmdserver,
                 prereposetups=[self._reposetup],
             )
         finally:
             gc.collect()  # trigger __del__ since worker process uses os._exit
 
     def _reposetup(self, ui, repo):
         if not repo.local():
             return
 
         class unixcmdserverrepo(repo.__class__):
             def close(self):
                 super(unixcmdserverrepo, self).close()
                 try:
                     self._cmdserveripc.send(self.root)
                 except socket.error:
                     self.ui.log(
                         b'cmdserver', b'failed to send repo root to master\n'
                     )
 
         repo.__class__ = unixcmdserverrepo
         repo._cmdserveripc = self._workeripc
 
         cachedrepo = self._repoloader.get(repo.root)
         if cachedrepo is None:
             return
         repo.ui.log(b'repocache', b'repo from cache: %s\n', repo.root)
         repocache.copycache(cachedrepo, repo)

mercurial/worker.py

@@ -1,473 +1,469 b''
 # worker.py - master-slave parallelism support
 #
 # Copyright 2013 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 
 import errno
 import os
 import pickle
+import selectors
 import signal
 import sys
 import threading
 import time
 
-try:
-    import selectors
-
-    selectors.BaseSelector
-except ImportError:
-    from .thirdparty import selectors2 as selectors
-
 from .i18n import _
 from . import (
     encoding,
     error,
     pycompat,
     scmutil,
 )
 
 
 def countcpus():
     '''try to count the number of CPUs on the system'''
 
     # posix
     try:
         n = int(os.sysconf('SC_NPROCESSORS_ONLN'))
         if n > 0:
             return n
     except (AttributeError, ValueError):
         pass
 
     # windows
     try:
         n = int(encoding.environ[b'NUMBER_OF_PROCESSORS'])
         if n > 0:
             return n
     except (KeyError, ValueError):
         pass
 
     return 1
 
 
 def _numworkers(ui):
     s = ui.config(b'worker', b'numcpus')
     if s:
         try:
             n = int(s)
             if n >= 1:
                 return n
         except ValueError:
             raise error.Abort(_(b'number of cpus must be an integer'))
     return min(max(countcpus(), 4), 32)
 
 
 def ismainthread():
     return threading.current_thread() == threading.main_thread()
 
 
 class _blockingreader:
     """Wrap unbuffered stream such that pickle.load() works with it.
 
     pickle.load() expects that calls to read() and readinto() read as many
     bytes as requested. On EOF, it is fine to read fewer bytes. In this case,
     pickle.load() raises an EOFError.
     """
 
     def __init__(self, wrapped):
         self._wrapped = wrapped
 
     def readline(self):
         return self._wrapped.readline()
 
     def readinto(self, buf):
         pos = 0
         size = len(buf)
 
         with memoryview(buf) as view:
             while pos < size:
                 with view[pos:] as subview:
                     ret = self._wrapped.readinto(subview)
                 if not ret:
                     break
                 pos += ret
 
         return pos
 
     # issue multiple reads until size is fulfilled (or EOF is encountered)
     def read(self, size=-1):
         if size < 0:
             return self._wrapped.readall()
 
         buf = bytearray(size)
         n_read = self.readinto(buf)
         del buf[n_read:]
         return bytes(buf)
 
 
 if pycompat.isposix or pycompat.iswindows:
     _STARTUP_COST = 0.01
     # The Windows worker is thread based. If tasks are CPU bound, threads
     # in the presence of the GIL result in excessive context switching and
     # this overhead can slow down execution.
     _DISALLOW_THREAD_UNSAFE = pycompat.iswindows
 else:
     _STARTUP_COST = 1e30
     _DISALLOW_THREAD_UNSAFE = False
 
 
 def worthwhile(ui, costperop, nops, threadsafe=True):
     """try to determine whether the benefit of multiple processes can
     outweigh the cost of starting them"""
 
     if not threadsafe and _DISALLOW_THREAD_UNSAFE:
         return False
 
     linear = costperop * nops
     workers = _numworkers(ui)
     benefit = linear - (_STARTUP_COST * workers + linear / workers)
     return benefit >= 0.15
 
 
 def worker(
     ui, costperarg, func, staticargs, args, hasretval=False, threadsafe=True
 ):
     """run a function, possibly in parallel in multiple worker
     processes.
 
     returns a progress iterator
 
     costperarg - cost of a single task
 
     func - function to run. It is expected to return a progress iterator.
 
     staticargs - arguments to pass to every invocation of the function
 
     args - arguments to split into chunks, to pass to individual
     workers
 
     hasretval - when True, func and the current function return an progress
     iterator then a dict (encoded as an iterator that yield many (False, ..)
     then a (True, dict)). The dicts are joined in some arbitrary order, so
     overlapping keys are a bad idea.
 
     threadsafe - whether work items are thread safe and can be executed using
     a thread-based worker. Should be disabled for CPU heavy tasks that don't
     release the GIL.
     """
     enabled = ui.configbool(b'worker', b'enabled')
     if enabled and _platformworker is _posixworker and not ismainthread():
         # The POSIX worker has to install a handler for SIGCHLD.
         # Python up to 3.9 only allows this in the main thread.
         enabled = False
 
     if enabled and worthwhile(ui, costperarg, len(args), threadsafe=threadsafe):
         return _platformworker(ui, func, staticargs, args, hasretval)
     return func(*staticargs + (args,))
 
 
 def _posixworker(ui, func, staticargs, args, hasretval):
     workers = _numworkers(ui)
     oldhandler = signal.getsignal(signal.SIGINT)
     signal.signal(signal.SIGINT, signal.SIG_IGN)
     pids, problem = set(), [0]
 
     def killworkers():
         # unregister SIGCHLD handler as all children will be killed. This
         # function shouldn't be interrupted by another SIGCHLD; otherwise pids
         # could be updated while iterating, which would cause inconsistency.
         signal.signal(signal.SIGCHLD, oldchldhandler)
         # if one worker bails, there's no good reason to wait for the rest
         for p in pids:
             try:
                 os.kill(p, signal.SIGTERM)
             except OSError as err:
                 if err.errno != errno.ESRCH:
                     raise
 
     def waitforworkers(blocking=True):
         for pid in pids.copy():
             p = st = 0
             while True:
                 try:
                     p, st = os.waitpid(pid, (0 if blocking else os.WNOHANG))
                     break
                 except OSError as e:
                     if e.errno == errno.EINTR:
                         continue
                     elif e.errno == errno.ECHILD:
                         # child would already be reaped, but pids yet been
                         # updated (maybe interrupted just after waitpid)
                         pids.discard(pid)
                         break
                     else:
                         raise
             if not p:
                 # skip subsequent steps, because child process should
                 # be still running in this case
                 continue
             pids.discard(p)
             st = _exitstatus(st)
             if st and not problem[0]:
                 problem[0] = st
 
     def sigchldhandler(signum, frame):
         waitforworkers(blocking=False)
         if problem[0]:
             killworkers()
 
     oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler)
     ui.flush()
     parentpid = os.getpid()
     pipes = []
     retval = {}
     for pargs in partition(args, min(workers, len(args))):
         # Every worker gets its own pipe to send results on, so we don't have to
         # implement atomic writes larger than PIPE_BUF. Each forked process has
         # its own pipe's descriptors in the local variables, and the parent
         # process has the full list of pipe descriptors (and it doesn't really
         # care what order they're in).
         rfd, wfd = os.pipe()
         pipes.append((rfd, wfd))
         # make sure we use os._exit in all worker code paths. otherwise the
         # worker may do some clean-ups which could cause surprises like
         # deadlock. see sshpeer.cleanup for example.
         # override error handling *before* fork. this is necessary because
         # exception (signal) may arrive after fork, before "pid =" assignment
         # completes, and other exception handler (dispatch.py) can lead to
         # unexpected code path without os._exit.
         ret = -1
         try:
             pid = os.fork()
             if pid == 0:
                 signal.signal(signal.SIGINT, oldhandler)
                 signal.signal(signal.SIGCHLD, oldchldhandler)
 
                 def workerfunc():
                     for r, w in pipes[:-1]:
                         os.close(r)
                         os.close(w)
                     os.close(rfd)
                     with os.fdopen(wfd, 'wb') as wf:
                         for result in func(*(staticargs + (pargs,))):
                             pickle.dump(result, wf)
                             wf.flush()
                     return 0
 
                 ret = scmutil.callcatch(ui, workerfunc)
         except:  # parent re-raises, child never returns
             if os.getpid() == parentpid:
                 raise
             exctype = sys.exc_info()[0]
             force = not issubclass(exctype, KeyboardInterrupt)
             ui.traceback(force=force)
         finally:
             if os.getpid() != parentpid:
                 try:
                     ui.flush()
                 except:  # never returns, no re-raises
                     pass
                 finally:
                     os._exit(ret & 255)
         pids.add(pid)
     selector = selectors.DefaultSelector()
     for rfd, wfd in pipes:
         os.close(wfd)
         # The stream has to be unbuffered. Otherwise, if all data is read from
         # the raw file into the buffer, the selector thinks that the FD is not
         # ready to read while pickle.load() could read from the buffer. This
         # would delay the processing of readable items.
         selector.register(os.fdopen(rfd, 'rb', 0), selectors.EVENT_READ)
 
     def cleanup():
         signal.signal(signal.SIGINT, oldhandler)
         waitforworkers()
         signal.signal(signal.SIGCHLD, oldchldhandler)
         selector.close()
         return problem[0]
 
     try:
         openpipes = len(pipes)
         while openpipes > 0:
             for key, events in selector.select():
                 try:
                     # The pytype error likely goes away on a modern version of
                     # pytype having a modern typeshed snapshot.
                     # pytype: disable=wrong-arg-types
                     res = pickle.load(_blockingreader(key.fileobj))
                     # pytype: enable=wrong-arg-types
                     if hasretval and res[0]:
                         retval.update(res[1])
                     else:
                         yield res
                 except EOFError:
                     selector.unregister(key.fileobj)
+                    # pytype: disable=attribute-error
                     key.fileobj.close()
+                    # pytype: enable=attribute-error
                     openpipes -= 1
                 except IOError as e:
                     if e.errno == errno.EINTR:
                         continue
                     raise
     except:  # re-raises
         killworkers()
         cleanup()
         raise
     status = cleanup()
     if status:
         if status < 0:
             os.kill(os.getpid(), -status)
         raise error.WorkerError(status)
     if hasretval:
         yield True, retval
 
 
 def _posixexitstatus(code):
     """convert a posix exit status into the same form returned by
     os.spawnv
 
     returns None if the process was stopped instead of exiting"""
     if os.WIFEXITED(code):
         return os.WEXITSTATUS(code)
     elif os.WIFSIGNALED(code):
         return -(os.WTERMSIG(code))
 
 
 def _windowsworker(ui, func, staticargs, args, hasretval):
     class Worker(threading.Thread):
         def __init__(
             self, taskqueue, resultqueue, func, staticargs, *args, **kwargs
         ):
             threading.Thread.__init__(self, *args, **kwargs)
             self._taskqueue = taskqueue
             self._resultqueue = resultqueue
             self._func = func
             self._staticargs = staticargs
             self._interrupted = False
             self.daemon = True
             self.exception = None
 
         def interrupt(self):
             self._interrupted = True
 
         def run(self):
             try:
                 while not self._taskqueue.empty():
                     try:
                         args = self._taskqueue.get_nowait()
                         for res in self._func(*self._staticargs + (args,)):
                             self._resultqueue.put(res)
                             # threading doesn't provide a native way to
                             # interrupt execution. handle it manually at every
                             # iteration.
                             if self._interrupted:
                                 return
                     except pycompat.queue.Empty:
                         break
             except Exception as e:
                 # store the exception such that the main thread can resurface
                 # it as if the func was running without workers.
                 self.exception = e
                 raise
 
     threads = []
 
     def trykillworkers():
         # Allow up to 1 second to clean worker threads nicely
         cleanupend = time.time() + 1
         for t in threads:
             t.interrupt()
         for t in threads:
             remainingtime = cleanupend - time.time()
             t.join(remainingtime)
             if t.is_alive():
                 # pass over the workers joining failure. it is more
                 # important to surface the inital exception than the
                 # fact that one of workers may be processing a large
                 # task and does not get to handle the interruption.
                 ui.warn(
                     _(
                         b"failed to kill worker threads while "
                         b"handling an exception\n"
                     )
                 )
                 return
 
     workers = _numworkers(ui)
     resultqueue = pycompat.queue.Queue()
     taskqueue = pycompat.queue.Queue()
     retval = {}
     # partition work to more pieces than workers to minimize the chance
     # of uneven distribution of large tasks between the workers
     for pargs in partition(args, workers * 20):
         taskqueue.put(pargs)
     for _i in range(workers):
         t = Worker(taskqueue, resultqueue, func, staticargs)
         threads.append(t)
         t.start()
     try:
         while len(threads) > 0:
             while not resultqueue.empty():
                 res = resultqueue.get()
                 if hasretval and res[0]:
                     retval.update(res[1])
                 else:
                     yield res
             threads[0].join(0.05)
             finishedthreads = [_t for _t in threads if not _t.is_alive()]
             for t in finishedthreads:
                 if t.exception is not None:
                     raise t.exception
                 threads.remove(t)
     except (Exception, KeyboardInterrupt):  # re-raises
         trykillworkers()
         raise
     while not resultqueue.empty():
         res = resultqueue.get()
         if hasretval and res[0]:
             retval.update(res[1])
         else:
             yield res
     if hasretval:
         yield True, retval
 
 
 if pycompat.iswindows:
     _platformworker = _windowsworker
 else:
     _platformworker = _posixworker
     _exitstatus = _posixexitstatus
 
 
 def partition(lst, nslices):
     """partition a list into N slices of roughly equal size
 
     The current strategy takes every Nth element from the input. If
     we ever write workers that need to preserve grouping in input
     we should consider allowing callers to specify a partition strategy.
 
     olivia is not a fan of this partitioning strategy when files are involved.
     In his words:
 
         Single-threaded Mercurial makes a point of creating and visiting
         files in a fixed order (alphabetical). When creating files in order,
         a typical filesystem is likely to allocate them on nearby regions on
         disk. Thus, when revisiting in the same order, locality is maximized
         and various forms of OS and disk-level caching and read-ahead get a
         chance to work.
 
         This effect can be quite significant on spinning disks. I discovered it
         circa Mercurial v0.4 when revlogs were named by hashes of filenames.
         Tarring a repo and copying it to another disk effectively randomized
         the revlog ordering on disk by sorting the revlogs by hash and suddenly
         performance of my kernel checkout benchmark dropped by ~10x because the
         "working set" of sectors visited no longer fit in the drive's cache and
         the workload switched from streaming to random I/O.
 
         What we should really be doing is have workers read filenames from a
         ordered queue. This preserves locality and also keeps any worker from
         getting more than one file out of balance.
     """
     for i in range(nslices):
         yield lst[i::nslices]