typing: add basic type hints to vfs.py

Again, there's a lot more that could be done, but this sticks to the obviously
correct stuff that is related to primitives or `vfs` objects.  Hopefully this
helps smoke out more path related bytes vs str issues in TortoiseHg.

PyCharm seems smart enough to apply hints from annotated superclass functions,
but pytype isn't (according to the *.pyi file generated), so those are annotated
too.

There was some discussion about changing the default path arg from `None` to
`b''` in order to avoid the more verbose `Optional` declarations.  This would be
more in line with `os.path.join()` (which rejects `None`, but ignores empty
strings), and still not change the behavior for callers still passing `None`
(because the check is `if path` instead of an explicit check for `None`).  But I
didn't want to hold this up while discussing that, so this documents what _is_.

mercurial/vfs.py

@@ -1,768 +1,788 b''
 # vfs.py - Mercurial 'vfs' classes
 #
 #  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 contextlib
 import os
 import shutil
 import stat
 import threading
 
+from typing import (
+    Optional,
+)
+
 from .i18n import _
 from .pycompat import (
     delattr,
     getattr,
     setattr,
 )
 from . import (
     encoding,
     error,
     pathutil,
     pycompat,
     util,
 )
 
 
-def _avoidambig(path, oldstat):
+def _avoidambig(path: bytes, oldstat):
     """Avoid file stat ambiguity forcibly
 
     This function causes copying ``path`` file, if it is owned by
     another (see issue5418 and issue5584 for detail).
     """
 
     def checkandavoid():
         newstat = util.filestat.frompath(path)
         # return whether file stat ambiguity is (already) avoided
         return not newstat.isambig(oldstat) or newstat.avoidambig(path, oldstat)
 
     if not checkandavoid():
         # simply copy to change owner of path to get privilege to
         # advance mtime (see issue5418)
         util.rename(util.mktempcopy(path), path)
         checkandavoid()
 
 
 class abstractvfs:
     """Abstract base class; cannot be instantiated"""
 
     # default directory separator for vfs
     #
     # Other vfs code always use `/` and this works fine because python file API
     # abstract the use of `/` and make it work transparently. For consistency
     # vfs will always use `/` when joining. This avoid some confusion in
     # encoded vfs (see issue6546)
     _dir_sep = b'/'
 
     def __init__(self, *args, **kwargs):
         '''Prevent instantiation; don't call this from subclasses.'''
         raise NotImplementedError('attempted instantiating ' + str(type(self)))
 
-    def __call__(self, path, mode=b'rb', **kwargs):
+    # TODO: type return, which is util.posixfile wrapped by a proxy
+    def __call__(self, path: bytes, mode: bytes = b'rb', **kwargs):
         raise NotImplementedError
 
-    def _auditpath(self, path, mode):
+    def _auditpath(self, path: bytes, mode: bytes):
         raise NotImplementedError
 
-    def join(self, path, *insidef):
+    def join(self, path: Optional[bytes], *insidef: bytes) -> bytes:
         raise NotImplementedError
 
-    def tryread(self, path):
+    def tryread(self, path: bytes) -> bytes:
         '''gracefully return an empty string for missing files'''
         try:
             return self.read(path)
         except FileNotFoundError:
             pass
         return b""
 
-    def tryreadlines(self, path, mode=b'rb'):
+    def tryreadlines(self, path: bytes, mode: bytes = b'rb'):
         '''gracefully return an empty array for missing files'''
         try:
             return self.readlines(path, mode=mode)
         except FileNotFoundError:
             pass
         return []
 
     @util.propertycache
     def open(self):
         """Open ``path`` file, which is relative to vfs root.
 
         Newly created directories are marked as "not to be indexed by
         the content indexing service", if ``notindexed`` is specified
         for "write" mode access.
         """
         return self.__call__
 
-    def read(self, path):
+    def read(self, path: bytes) -> bytes:
         with self(path, b'rb') as fp:
             return fp.read()
 
-    def readlines(self, path, mode=b'rb'):
+    def readlines(self, path: bytes, mode: bytes = b'rb'):
         with self(path, mode=mode) as fp:
             return fp.readlines()
 
-    def write(self, path, data, backgroundclose=False, **kwargs):
+    def write(
+        self, path: bytes, data: bytes, backgroundclose=False, **kwargs
+    ) -> int:
         with self(path, b'wb', backgroundclose=backgroundclose, **kwargs) as fp:
             return fp.write(data)
 
-    def writelines(self, path, data, mode=b'wb', notindexed=False):
+    def writelines(
+        self, path: bytes, data: bytes, mode: bytes = b'wb', notindexed=False
+    ) -> None:
         with self(path, mode=mode, notindexed=notindexed) as fp:
             return fp.writelines(data)
 
-    def append(self, path, data):
+    def append(self, path: bytes, data: bytes) -> int:
         with self(path, b'ab') as fp:
             return fp.write(data)
 
-    def basename(self, path):
+    def basename(self, path: bytes) -> bytes:
         """return base element of a path (as os.path.basename would do)
 
         This exists to allow handling of strange encoding if needed."""
         return os.path.basename(path)
 
-    def chmod(self, path, mode):
+    def chmod(self, path: bytes, mode: int) -> None:
         return os.chmod(self.join(path), mode)
 
-    def dirname(self, path):
+    def dirname(self, path: bytes) -> bytes:
         """return dirname element of a path (as os.path.dirname would do)
 
         This exists to allow handling of strange encoding if needed."""
         return os.path.dirname(path)
 
-    def exists(self, path=None):
+    def exists(self, path: Optional[bytes] = None) -> bool:
         return os.path.exists(self.join(path))
 
     def fstat(self, fp):
         return util.fstat(fp)
 
-    def isdir(self, path=None):
+    def isdir(self, path: Optional[bytes] = None) -> bool:
         return os.path.isdir(self.join(path))
 
-    def isfile(self, path=None):
+    def isfile(self, path: Optional[bytes] = None) -> bool:
         return os.path.isfile(self.join(path))
 
-    def islink(self, path=None):
+    def islink(self, path: Optional[bytes] = None) -> bool:
         return os.path.islink(self.join(path))
 
-    def isfileorlink(self, path=None):
+    def isfileorlink(self, path: Optional[bytes] = None) -> bool:
         """return whether path is a regular file or a symlink
 
         Unlike isfile, this doesn't follow symlinks."""
         try:
             st = self.lstat(path)
         except OSError:
             return False
         mode = st.st_mode
         return stat.S_ISREG(mode) or stat.S_ISLNK(mode)
 
-    def _join(self, *paths):
+    def _join(self, *paths: bytes) -> bytes:
         root_idx = 0
         for idx, p in enumerate(paths):
             if os.path.isabs(p) or p.startswith(self._dir_sep):
                 root_idx = idx
         if root_idx != 0:
             paths = paths[root_idx:]
         paths = [p for p in paths if p]
         return self._dir_sep.join(paths)
 
-    def reljoin(self, *paths):
+    def reljoin(self, *paths: bytes) -> bytes:
         """join various elements of a path together (as os.path.join would do)
 
         The vfs base is not injected so that path stay relative. This exists
         to allow handling of strange encoding if needed."""
         return self._join(*paths)
 
-    def split(self, path):
+    def split(self, path: bytes):
         """split top-most element of a path (as os.path.split would do)
 
         This exists to allow handling of strange encoding if needed."""
         return os.path.split(path)
 
-    def lexists(self, path=None):
+    def lexists(self, path: Optional[bytes] = None) -> bool:
         return os.path.lexists(self.join(path))
 
-    def lstat(self, path=None):
+    def lstat(self, path: Optional[bytes] = None):
         return os.lstat(self.join(path))
 
-    def listdir(self, path=None):
+    def listdir(self, path: Optional[bytes] = None):
         return os.listdir(self.join(path))
 
-    def makedir(self, path=None, notindexed=True):
+    def makedir(self, path: Optional[bytes] = None, notindexed=True):
         return util.makedir(self.join(path), notindexed)
 
-    def makedirs(self, path=None, mode=None):
+    def makedirs(
+        self, path: Optional[bytes] = None, mode: Optional[int] = None
+    ):
         return util.makedirs(self.join(path), mode)
 
-    def makelock(self, info, path):
+    def makelock(self, info, path: bytes):
         return util.makelock(info, self.join(path))
 
-    def mkdir(self, path=None):
+    def mkdir(self, path: Optional[bytes] = None):
         return os.mkdir(self.join(path))
 
-    def mkstemp(self, suffix=b'', prefix=b'tmp', dir=None):
+    def mkstemp(
+        self,
+        suffix: bytes = b'',
+        prefix: bytes = b'tmp',
+        dir: Optional[bytes] = None,
+    ):
         fd, name = pycompat.mkstemp(
             suffix=suffix, prefix=prefix, dir=self.join(dir)
         )
         dname, fname = util.split(name)
         if dir:
             return fd, os.path.join(dir, fname)
         else:
             return fd, fname
 
-    def readdir(self, path=None, stat=None, skip=None):
+    def readdir(self, path: Optional[bytes] = None, stat=None, skip=None):
         return util.listdir(self.join(path), stat, skip)
 
-    def readlock(self, path):
+    def readlock(self, path: bytes) -> bytes:
         return util.readlock(self.join(path))
 
-    def rename(self, src, dst, checkambig=False):
+    def rename(self, src: bytes, dst: bytes, checkambig=False):
         """Rename from src to dst
 
         checkambig argument is used with util.filestat, and is useful
         only if destination file is guarded by any lock
         (e.g. repo.lock or repo.wlock).
 
         To avoid file stat ambiguity forcibly, checkambig=True involves
         copying ``src`` file, if it is owned by another. Therefore, use
         checkambig=True only in limited cases (see also issue5418 and
         issue5584 for detail).
         """
         self._auditpath(dst, b'w')
         srcpath = self.join(src)
         dstpath = self.join(dst)
         oldstat = checkambig and util.filestat.frompath(dstpath)
         if oldstat and oldstat.stat:
             ret = util.rename(srcpath, dstpath)
             _avoidambig(dstpath, oldstat)
             return ret
         return util.rename(srcpath, dstpath)
 
-    def readlink(self, path):
+    def readlink(self, path: bytes) -> bytes:
         return util.readlink(self.join(path))
 
-    def removedirs(self, path=None):
+    def removedirs(self, path: Optional[bytes] = None):
         """Remove a leaf directory and all empty intermediate ones"""
         return util.removedirs(self.join(path))
 
-    def rmdir(self, path=None):
+    def rmdir(self, path: Optional[bytes] = None):
         """Remove an empty directory."""
         return os.rmdir(self.join(path))
 
-    def rmtree(self, path=None, ignore_errors=False, forcibly=False):
+    def rmtree(
+        self, path: Optional[bytes] = None, ignore_errors=False, forcibly=False
+    ):
         """Remove a directory tree recursively
 
         If ``forcibly``, this tries to remove READ-ONLY files, too.
         """
         if forcibly:
 
             def onerror(function, path, excinfo):
                 if function is not os.remove:
                     raise
                 # read-only files cannot be unlinked under Windows
                 s = os.stat(path)
                 if (s.st_mode & stat.S_IWRITE) != 0:
                     raise
                 os.chmod(path, stat.S_IMODE(s.st_mode) | stat.S_IWRITE)
                 os.remove(path)
 
         else:
             onerror = None
         return shutil.rmtree(
             self.join(path), ignore_errors=ignore_errors, onerror=onerror
         )
 
-    def setflags(self, path, l, x):
+    def setflags(self, path: bytes, l: bool, x: bool):
         return util.setflags(self.join(path), l, x)
 
-    def stat(self, path=None):
+    def stat(self, path: Optional[bytes] = None):
         return os.stat(self.join(path))
 
-    def unlink(self, path=None):
+    def unlink(self, path: Optional[bytes] = None):
         return util.unlink(self.join(path))
 
-    def tryunlink(self, path=None):
+    def tryunlink(self, path: Optional[bytes] = None):
         """Attempt to remove a file, ignoring missing file errors."""
         util.tryunlink(self.join(path))
 
-    def unlinkpath(self, path=None, ignoremissing=False, rmdir=True):
+    def unlinkpath(
+        self, path: Optional[bytes] = None, ignoremissing=False, rmdir=True
+    ):
         return util.unlinkpath(
             self.join(path), ignoremissing=ignoremissing, rmdir=rmdir
         )
 
-    def utime(self, path=None, t=None):
+    def utime(self, path: Optional[bytes] = None, t=None):
         return os.utime(self.join(path), t)
 
-    def walk(self, path=None, onerror=None):
+    def walk(self, path: Optional[bytes] = None, onerror=None):
         """Yield (dirpath, dirs, files) tuple for each directories under path
 
         ``dirpath`` is relative one from the root of this vfs. This
         uses ``os.sep`` as path separator, even you specify POSIX
         style ``path``.
 
         "The root of this vfs" is represented as empty ``dirpath``.
         """
         root = os.path.normpath(self.join(None))
         # when dirpath == root, dirpath[prefixlen:] becomes empty
         # because len(dirpath) < prefixlen.
         prefixlen = len(pathutil.normasprefix(root))
         for dirpath, dirs, files in os.walk(self.join(path), onerror=onerror):
             yield (dirpath[prefixlen:], dirs, files)
 
     @contextlib.contextmanager
     def backgroundclosing(self, ui, expectedcount=-1):
         """Allow files to be closed asynchronously.
 
         When this context manager is active, ``backgroundclose`` can be passed
         to ``__call__``/``open`` to result in the file possibly being closed
         asynchronously, on a background thread.
         """
         # Sharing backgroundfilecloser between threads is complex and using
         # multiple instances puts us at risk of running out of file descriptors
         # only allow to use backgroundfilecloser when in main thread.
         if not isinstance(
             threading.current_thread(),
             threading._MainThread,  # pytype: disable=module-attr
         ):
             yield
             return
         vfs = getattr(self, 'vfs', self)
         if getattr(vfs, '_backgroundfilecloser', None):
             raise error.Abort(
                 _(b'can only have 1 active background file closer')
             )
 
         with backgroundfilecloser(ui, expectedcount=expectedcount) as bfc:
             try:
                 vfs._backgroundfilecloser = (
                     bfc  # pytype: disable=attribute-error
                 )
                 yield bfc
             finally:
                 vfs._backgroundfilecloser = (
                     None  # pytype: disable=attribute-error
                 )
 
     def register_file(self, path):
         """generic hook point to lets fncache steer its stew"""
 
 
 class vfs(abstractvfs):
     """Operate files relative to a base directory
 
     This class is used to hide the details of COW semantics and
     remote file access from higher level code.
 
     'cacheaudited' should be enabled only if (a) vfs object is short-lived, or
     (b) the base directory is managed by hg and considered sort-of append-only.
     See pathutil.pathauditor() for details.
     """
 
     def __init__(
         self,
-        base,
+        base: bytes,
         audit=True,
         cacheaudited=False,
         expandpath=False,
         realpath=False,
     ):
         if expandpath:
             base = util.expandpath(base)
         if realpath:
             base = os.path.realpath(base)
         self.base = base
         self._audit = audit
         if audit:
             self.audit = pathutil.pathauditor(self.base, cached=cacheaudited)
         else:
             self.audit = lambda path, mode=None: True
         self.createmode = None
         self._trustnlink = None
         self.options = {}
 
     @util.propertycache
-    def _cansymlink(self):
+    def _cansymlink(self) -> bool:
         return util.checklink(self.base)
 
     @util.propertycache
     def _chmod(self):
         return util.checkexec(self.base)
 
     def _fixfilemode(self, name):
         if self.createmode is None or not self._chmod:
             return
         os.chmod(name, self.createmode & 0o666)
 
-    def _auditpath(self, path, mode):
+    def _auditpath(self, path, mode) -> None:
         if self._audit:
             if os.path.isabs(path) and path.startswith(self.base):
                 path = os.path.relpath(path, self.base)
             r = util.checkosfilename(path)
             if r:
                 raise error.Abort(b"%s: %r" % (r, path))
             self.audit(path, mode=mode)
 
     def __call__(
         self,
-        path,
-        mode=b"r",
+        path: bytes,
+        mode: bytes = b"r",
         atomictemp=False,
         notindexed=False,
         backgroundclose=False,
         checkambig=False,
         auditpath=True,
         makeparentdirs=True,
     ):
         """Open ``path`` file, which is relative to vfs root.
 
         By default, parent directories are created as needed. Newly created
         directories are marked as "not to be indexed by the content indexing
         service", if ``notindexed`` is specified for "write" mode access.
         Set ``makeparentdirs=False`` to not create directories implicitly.
 
         If ``backgroundclose`` is passed, the file may be closed asynchronously.
         It can only be used if the ``self.backgroundclosing()`` context manager
         is active. This should only be specified if the following criteria hold:
 
         1. There is a potential for writing thousands of files. Unless you
            are writing thousands of files, the performance benefits of
            asynchronously closing files is not realized.
         2. Files are opened exactly once for the ``backgroundclosing``
            active duration and are therefore free of race conditions between
            closing a file on a background thread and reopening it. (If the
            file were opened multiple times, there could be unflushed data
            because the original file handle hasn't been flushed/closed yet.)
 
         ``checkambig`` argument is passed to atomictempfile (valid
         only for writing), and is useful only if target file is
         guarded by any lock (e.g. repo.lock or repo.wlock).
 
         To avoid file stat ambiguity forcibly, checkambig=True involves
         copying ``path`` file opened in "append" mode (e.g. for
         truncation), if it is owned by another. Therefore, use
         combination of append mode and checkambig=True only in limited
         cases (see also issue5418 and issue5584 for detail).
         """
         if auditpath:
             self._auditpath(path, mode)
         f = self.join(path)
 
         if b"b" not in mode:
             mode += b"b"  # for that other OS
 
         nlink = -1
         if mode not in (b'r', b'rb'):
             dirname, basename = util.split(f)
             # If basename is empty, then the path is malformed because it points
             # to a directory. Let the posixfile() call below raise IOError.
             if basename:
                 if atomictemp:
                     if makeparentdirs:
                         util.makedirs(dirname, self.createmode, notindexed)
                     return util.atomictempfile(
                         f, mode, self.createmode, checkambig=checkambig
                     )
                 try:
                     if b'w' in mode:
                         util.unlink(f)
                         nlink = 0
                     else:
                         # nlinks() may behave differently for files on Windows
                         # shares if the file is open.
                         with util.posixfile(f):
                             nlink = util.nlinks(f)
                             if nlink < 1:
                                 nlink = 2  # force mktempcopy (issue1922)
                 except FileNotFoundError:
                     nlink = 0
                     if makeparentdirs:
                         util.makedirs(dirname, self.createmode, notindexed)
                 if nlink > 0:
                     if self._trustnlink is None:
                         self._trustnlink = nlink > 1 or util.checknlink(f)
                     if nlink > 1 or not self._trustnlink:
                         util.rename(util.mktempcopy(f), f)
         fp = util.posixfile(f, mode)
         if nlink == 0:
             self._fixfilemode(f)
 
         if checkambig:
             if mode in (b'r', b'rb'):
                 raise error.Abort(
                     _(
                         b'implementation error: mode %s is not'
                         b' valid for checkambig=True'
                     )
                     % mode
                 )
             fp = checkambigatclosing(fp)
 
         if backgroundclose and isinstance(
             threading.current_thread(),
             threading._MainThread,  # pytype: disable=module-attr
         ):
             if (
                 not self._backgroundfilecloser  # pytype: disable=attribute-error
             ):
                 raise error.Abort(
                     _(
                         b'backgroundclose can only be used when a '
                         b'backgroundclosing context manager is active'
                     )
                 )
 
             fp = delayclosedfile(
                 fp,
                 self._backgroundfilecloser,  # pytype: disable=attribute-error
             )
 
         return fp
 
-    def symlink(self, src, dst):
+    def symlink(self, src: bytes, dst: bytes) -> None:
         self.audit(dst)
         linkname = self.join(dst)
         util.tryunlink(linkname)
 
         util.makedirs(os.path.dirname(linkname), self.createmode)
 
         if self._cansymlink:
             try:
                 os.symlink(src, linkname)
             except OSError as err:
                 raise OSError(
                     err.errno,
                     _(b'could not symlink to %r: %s')
                     % (src, encoding.strtolocal(err.strerror)),
                     linkname,
                 )
         else:
             self.write(dst, src)
 
-    def join(self, path, *insidef):
+    def join(self, path: Optional[bytes], *insidef: bytes) -> bytes:
         if path:
             parts = [self.base, path]
             parts.extend(insidef)
             return self._join(*parts)
         else:
             return self.base
 
 
 opener = vfs
 
 
 class proxyvfs(abstractvfs):
-    def __init__(self, vfs):
+    def __init__(self, vfs: "vfs"):
         self.vfs = vfs
 
     def _auditpath(self, path, mode):
         return self.vfs._auditpath(path, mode)
 
     @property
     def options(self):
         return self.vfs.options
 
     @options.setter
     def options(self, value):
         self.vfs.options = value
 
 
 class filtervfs(proxyvfs, abstractvfs):
     '''Wrapper vfs for filtering filenames with a function.'''
 
-    def __init__(self, vfs, filter):
+    def __init__(self, vfs: "vfs", filter):
         proxyvfs.__init__(self, vfs)
         self._filter = filter
 
-    def __call__(self, path, *args, **kwargs):
+    def __call__(self, path: bytes, *args, **kwargs):
         return self.vfs(self._filter(path), *args, **kwargs)
 
-    def join(self, path, *insidef):
+    def join(self, path: Optional[bytes], *insidef: bytes) -> bytes:
         if path:
             return self.vfs.join(self._filter(self.vfs.reljoin(path, *insidef)))
         else:
             return self.vfs.join(path)
 
 
 filteropener = filtervfs
 
 
 class readonlyvfs(proxyvfs):
     '''Wrapper vfs preventing any writing.'''
 
-    def __init__(self, vfs):
+    def __init__(self, vfs: "vfs"):
         proxyvfs.__init__(self, vfs)
 
-    def __call__(self, path, mode=b'r', *args, **kw):
+    def __call__(self, path: bytes, mode: bytes = b'r', *args, **kw):
         if mode not in (b'r', b'rb'):
             raise error.Abort(_(b'this vfs is read only'))
         return self.vfs(path, mode, *args, **kw)
 
-    def join(self, path, *insidef):
+    def join(self, path: Optional[bytes], *insidef: bytes) -> bytes:
         return self.vfs.join(path, *insidef)
 
 
 class closewrapbase:
     """Base class of wrapper, which hooks closing
 
     Do not instantiate outside of the vfs layer.
     """
 
     def __init__(self, fh):
         object.__setattr__(self, '_origfh', fh)
 
     def __getattr__(self, attr):
         return getattr(self._origfh, attr)
 
     def __setattr__(self, attr, value):
         return setattr(self._origfh, attr, value)
 
     def __delattr__(self, attr):
         return delattr(self._origfh, attr)
 
     def __enter__(self):
         self._origfh.__enter__()
         return self
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         raise NotImplementedError('attempted instantiating ' + str(type(self)))
 
     def close(self):
         raise NotImplementedError('attempted instantiating ' + str(type(self)))
 
 
 class delayclosedfile(closewrapbase):
     """Proxy for a file object whose close is delayed.
 
     Do not instantiate outside of the vfs layer.
     """
 
     def __init__(self, fh, closer):
         super(delayclosedfile, self).__init__(fh)
         object.__setattr__(self, '_closer', closer)
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         self._closer.close(self._origfh)
 
     def close(self):
         self._closer.close(self._origfh)
 
 
 class backgroundfilecloser:
     """Coordinates background closing of file handles on multiple threads."""
 
     def __init__(self, ui, expectedcount=-1):
         self._running = False
         self._entered = False
         self._threads = []
         self._threadexception = None
 
         # Only Windows/NTFS has slow file closing. So only enable by default
         # on that platform. But allow to be enabled elsewhere for testing.
         defaultenabled = pycompat.iswindows
         enabled = ui.configbool(b'worker', b'backgroundclose', defaultenabled)
 
         if not enabled:
             return
 
         # There is overhead to starting and stopping the background threads.
         # Don't do background processing unless the file count is large enough
         # to justify it.
         minfilecount = ui.configint(b'worker', b'backgroundcloseminfilecount')
         # FUTURE dynamically start background threads after minfilecount closes.
         # (We don't currently have any callers that don't know their file count)
         if expectedcount > 0 and expectedcount < minfilecount:
             return
 
         maxqueue = ui.configint(b'worker', b'backgroundclosemaxqueue')
         threadcount = ui.configint(b'worker', b'backgroundclosethreadcount')
 
         ui.debug(
             b'starting %d threads for background file closing\n' % threadcount
         )
 
         self._queue = pycompat.queue.Queue(maxsize=maxqueue)
         self._running = True
 
         for i in range(threadcount):
             t = threading.Thread(target=self._worker, name='backgroundcloser')
             self._threads.append(t)
             t.start()
 
     def __enter__(self):
         self._entered = True
         return self
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         self._running = False
 
         # Wait for threads to finish closing so open files don't linger for
         # longer than lifetime of context manager.
         for t in self._threads:
             t.join()
 
     def _worker(self):
         """Main routine for worker thread."""
         while True:
             try:
                 fh = self._queue.get(block=True, timeout=0.100)
                 # Need to catch or the thread will terminate and
                 # we could orphan file descriptors.
                 try:
                     fh.close()
                 except Exception as e:
                     # Stash so can re-raise from main thread later.
                     self._threadexception = e
             except pycompat.queue.Empty:
                 if not self._running:
                     break
 
     def close(self, fh):
         """Schedule a file for closing."""
         if not self._entered:
             raise error.Abort(
                 _(b'can only call close() when context manager active')
             )
 
         # If a background thread encountered an exception, raise now so we fail
         # fast. Otherwise we may potentially go on for minutes until the error
         # is acted on.
         if self._threadexception:
             e = self._threadexception
             self._threadexception = None
             raise e
 
         # If we're not actively running, close synchronously.
         if not self._running:
             fh.close()
             return
 
         self._queue.put(fh, block=True, timeout=None)
 
 
 class checkambigatclosing(closewrapbase):
     """Proxy for a file object, to avoid ambiguity of file stat
 
     See also util.filestat for detail about "ambiguity of file stat".
 
     This proxy is useful only if the target file is guarded by any
     lock (e.g. repo.lock or repo.wlock)
 
     Do not instantiate outside of the vfs layer.
     """
 
     def __init__(self, fh):
         super(checkambigatclosing, self).__init__(fh)
         object.__setattr__(self, '_oldstat', util.filestat.frompath(fh.name))
 
     def _checkambig(self):
         oldstat = self._oldstat
         if oldstat.stat:
             _avoidambig(self._origfh.name, oldstat)
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         self._origfh.__exit__(exc_type, exc_value, exc_tb)
         self._checkambig()
 
     def close(self):
         self._origfh.close()
         self._checkambig()