cpython.git - https://github.com/python/cpython.git

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"""Supporting definitions for the Python regression tests."""

if __name__ != 'test.support':
    raise ImportError('support must be imported from the test package')

import contextlib
import errno
import functools
import gc
import socket
import sys
import os
import platform
import shutil
import warnings
import unittest
import importlib
import collections.abc
import re
import subprocess
import imp
import time
import sysconfig
import fnmatch
import logging.handlers
import struct
import tempfile
import _testcapi

try:
    import _thread, threading
except ImportError:
    _thread = None
    threading = None
try:
    import multiprocessing.process
except ImportError:
    multiprocessing = None

try:
    import zlib
except ImportError:
    zlib = None

try:
    import bz2
except ImportError:
    bz2 = None

try:
    import lzma
except ImportError:
    lzma = None

__all__ = [
    "Error", "TestFailed", "ResourceDenied", "import_module", "verbose",
    "use_resources", "max_memuse", "record_original_stdout",
    "get_original_stdout", "unload", "unlink", "rmtree", "forget",
    "is_resource_enabled", "requires", "requires_freebsd_version",
    "requires_linux_version", "requires_mac_ver", "find_unused_port",
    "bind_port", "IPV6_ENABLED", "is_jython", "TESTFN", "HOST", "SAVEDCWD",
    "temp_cwd", "findfile", "create_empty_file", "sortdict",
    "check_syntax_error", "open_urlresource", "check_warnings", "CleanImport",
    "EnvironmentVarGuard", "TransientResource", "captured_stdout",
    "captured_stdin", "captured_stderr", "time_out", "socket_peer_reset",
    "ioerror_peer_reset", "run_with_locale", 'temp_umask',
    "transient_internet", "set_memlimit", "bigmemtest", "bigaddrspacetest",
    "BasicTestRunner", "run_unittest", "run_doctest", "threading_setup",
    "threading_cleanup", "reap_children", "cpython_only", "check_impl_detail",
    "get_attribute", "swap_item", "swap_attr", "requires_IEEE_754",
    "TestHandler", "Matcher", "can_symlink", "skip_unless_symlink",
    "skip_unless_xattr", "import_fresh_module", "requires_zlib",
    "PIPE_MAX_SIZE", "failfast", "anticipate_failure", "run_with_tz",
    "requires_bz2", "requires_lzma"
    ]

class Error(Exception):
    """Base class for regression test exceptions."""

class TestFailed(Error):
    """Test failed."""

class ResourceDenied(unittest.SkipTest):
    """Test skipped because it requested a disallowed resource.

    This is raised when a test calls requires() for a resource that
    has not be enabled.  It is used to distinguish between expected
    and unexpected skips.
    """

@contextlib.contextmanager
def _ignore_deprecated_imports(ignore=True):
    """Context manager to suppress package and module deprecation
    warnings when importing them.

    If ignore is False, this context manager has no effect."""
    if ignore:
        with warnings.catch_warnings():
            warnings.filterwarnings("ignore", ".+ (module|package)",
                                    DeprecationWarning)
            yield
    else:
        yield


def import_module(name, deprecated=False):
    """Import and return the module to be tested, raising SkipTest if
    it is not available.

    If deprecated is True, any module or package deprecation messages
    will be suppressed."""
    with _ignore_deprecated_imports(deprecated):
        try:
            return importlib.import_module(name)
        except ImportError as msg:
            raise unittest.SkipTest(str(msg))


def _save_and_remove_module(name, orig_modules):
    """Helper function to save and remove a module from sys.modules

       Raise ImportError if the module can't be imported."""
    # try to import the module and raise an error if it can't be imported
    if name not in sys.modules:
        __import__(name)
        del sys.modules[name]
    for modname in list(sys.modules):
        if modname == name or modname.startswith(name + '.'):
            orig_modules[modname] = sys.modules[modname]
            del sys.modules[modname]

def _save_and_block_module(name, orig_modules):
    """Helper function to save and block a module in sys.modules

       Return True if the module was in sys.modules, False otherwise."""
    saved = True
    try:
        orig_modules[name] = sys.modules[name]
    except KeyError:
        saved = False
    sys.modules[name] = None
    return saved


def anticipate_failure(condition):
    """Decorator to mark a test that is known to be broken in some cases

       Any use of this decorator should have a comment identifying the
       associated tracker issue.
    """
    if condition:
        return unittest.expectedFailure
    return lambda f: f


def import_fresh_module(name, fresh=(), blocked=(), deprecated=False):
    """Imports and returns a module, deliberately bypassing the sys.modules cache
    and importing a fresh copy of the module. Once the import is complete,
    the sys.modules cache is restored to its original state.

    Modules named in fresh are also imported anew if needed by the import.
    If one of these modules can't be imported, None is returned.

    Importing of modules named in blocked is prevented while the fresh import
    takes place.

    If deprecated is True, any module or package deprecation messages
    will be suppressed."""
    # NOTE: test_heapq, test_json and test_warnings include extra sanity checks
    # to make sure that this utility function is working as expected
    with _ignore_deprecated_imports(deprecated):
        # Keep track of modules saved for later restoration as well
        # as those which just need a blocking entry removed
        orig_modules = {}
        names_to_remove = []
        _save_and_remove_module(name, orig_modules)
        try:
            for fresh_name in fresh:
                _save_and_remove_module(fresh_name, orig_modules)
            for blocked_name in blocked:
                if not _save_and_block_module(blocked_name, orig_modules):
                    names_to_remove.append(blocked_name)
            fresh_module = importlib.import_module(name)
        except ImportError:
            fresh_module = None
        finally:
            for orig_name, module in orig_modules.items():
                sys.modules[orig_name] = module
            for name_to_remove in names_to_remove:
                del sys.modules[name_to_remove]
        return fresh_module


def get_attribute(obj, name):
    """Get an attribute, raising SkipTest if AttributeError is raised."""
    try:
        attribute = getattr(obj, name)
    except AttributeError:
        raise unittest.SkipTest("object %r has no attribute %r" % (obj, name))
    else:
        return attribute

verbose = 1              # Flag set to 0 by regrtest.py
use_resources = None     # Flag set to [] by regrtest.py
max_memuse = 0           # Disable bigmem tests (they will still be run with
                         # small sizes, to make sure they work.)
real_max_memuse = 0
failfast = False
match_tests = None

# _original_stdout is meant to hold stdout at the time regrtest began.
# This may be "the real" stdout, or IDLE's emulation of stdout, or whatever.
# The point is to have some flavor of stdout the user can actually see.
_original_stdout = None
def record_original_stdout(stdout):
    global _original_stdout
    _original_stdout = stdout

def get_original_stdout():
    return _original_stdout or sys.stdout

def unload(name):
    try:
        del sys.modules[name]
    except KeyError:
        pass

if sys.platform.startswith("win"):
    def _waitfor(func, pathname, waitall=False):
        # Peform the operation
        func(pathname)
        # Now setup the wait loop
        if waitall:
            dirname = pathname
        else:
            dirname, name = os.path.split(pathname)
            dirname = dirname or '.'
        # Check for `pathname` to be removed from the filesystem.
        # The exponential backoff of the timeout amounts to a total
        # of ~1 second after which the deletion is probably an error
        # anyway.
        # Testing on a i7@4.3GHz shows that usually only 1 iteration is
        # required when contention occurs.
        timeout = 0.001
        while timeout < 1.0:
            # Note we are only testing for the existance of the file(s) in
            # the contents of the directory regardless of any security or
            # access rights.  If we have made it this far, we have sufficient
            # permissions to do that much using Python's equivalent of the
            # Windows API FindFirstFile.
            # Other Windows APIs can fail or give incorrect results when
            # dealing with files that are pending deletion.
            L = os.listdir(dirname)
            if not (L if waitall else name in L):
                return
            # Increase the timeout and try again
            time.sleep(timeout)
            timeout *= 2
        warnings.warn('tests may fail, delete still pending for ' + pathname,
                      RuntimeWarning, stacklevel=4)

    def _unlink(filename):
        _waitfor(os.unlink, filename)

    def _rmdir(dirname):
        _waitfor(os.rmdir, dirname)

    def _rmtree(path):
        def _rmtree_inner(path):
            for name in os.listdir(path):
                fullname = os.path.join(path, name)
                if os.path.isdir(fullname):
                    _waitfor(_rmtree_inner, fullname, waitall=True)
                    os.rmdir(fullname)
                else:
                    os.unlink(fullname)
        _waitfor(_rmtree_inner, path, waitall=True)
        _waitfor(os.rmdir, path)
else:
    _unlink = os.unlink
    _rmdir = os.rmdir
    _rmtree = shutil.rmtree

def unlink(filename):
    try:
        _unlink(filename)
    except OSError as error:
        # The filename need not exist.
        if error.errno not in (errno.ENOENT, errno.ENOTDIR):
            raise

def rmdir(dirname):
    try:
        _rmdir(dirname)
    except OSError as error:
        # The directory need not exist.
        if error.errno != errno.ENOENT:
            raise

def rmtree(path):
    try:
        _rmtree(path)
    except OSError as error:
        if error.errno != errno.ENOENT:
            raise

def make_legacy_pyc(source):
    """Move a PEP 3147 pyc/pyo file to its legacy pyc/pyo location.

    The choice of .pyc or .pyo extension is done based on the __debug__ flag
    value.

    :param source: The file system path to the source file.  The source file
        does not need to exist, however the PEP 3147 pyc file must exist.
    :return: The file system path to the legacy pyc file.
    """
    pyc_file = imp.cache_from_source(source)
    up_one = os.path.dirname(os.path.abspath(source))
    legacy_pyc = os.path.join(up_one, source + ('c' if __debug__ else 'o'))
    os.rename(pyc_file, legacy_pyc)
    return legacy_pyc

def forget(modname):
    """'Forget' a module was ever imported.

    This removes the module from sys.modules and deletes any PEP 3147 or
    legacy .pyc and .pyo files.
    """
    unload(modname)
    for dirname in sys.path:
        source = os.path.join(dirname, modname + '.py')
        # It doesn't matter if they exist or not, unlink all possible
        # combinations of PEP 3147 and legacy pyc and pyo files.
        unlink(source + 'c')
        unlink(source + 'o')
        unlink(imp.cache_from_source(source, debug_override=True))
        unlink(imp.cache_from_source(source, debug_override=False))

# On some platforms, should not run gui test even if it is allowed
# in `use_resources'.
if sys.platform.startswith('win'):
    import ctypes
    import ctypes.wintypes
    def _is_gui_available():
        UOI_FLAGS = 1
        WSF_VISIBLE = 0x0001
        class USEROBJECTFLAGS(ctypes.Structure):
            _fields_ = [("fInherit", ctypes.wintypes.BOOL),
                        ("fReserved", ctypes.wintypes.BOOL),
                        ("dwFlags", ctypes.wintypes.DWORD)]
        dll = ctypes.windll.user32
        h = dll.GetProcessWindowStation()
        if not h:
            raise ctypes.WinError()
        uof = USEROBJECTFLAGS()
        needed = ctypes.wintypes.DWORD()
        res = dll.GetUserObjectInformationW(h,
            UOI_FLAGS,
            ctypes.byref(uof),
            ctypes.sizeof(uof),
            ctypes.byref(needed))
        if not res:
            raise ctypes.WinError()
        return bool(uof.dwFlags & WSF_VISIBLE)
else:
    def _is_gui_available():
        return True

def is_resource_enabled(resource):
    """Test whether a resource is enabled.  Known resources are set by
    regrtest.py."""
    return use_resources is not None and resource in use_resources

def requires(resource, msg=None):
    """Raise ResourceDenied if the specified resource is not available.

    If the caller's module is __main__ then automatically return True.  The
    possibility of False being returned occurs when regrtest.py is
    executing.
    """
    if resource == 'gui' and not _is_gui_available():
        raise unittest.SkipTest("Cannot use the 'gui' resource")
    # see if the caller's module is __main__ - if so, treat as if
    # the resource was set
    if sys._getframe(1).f_globals.get("__name__") == "__main__":
        return
    if not is_resource_enabled(resource):
        if msg is None:
            msg = "Use of the %r resource not enabled" % resource
        raise ResourceDenied(msg)

def _requires_unix_version(sysname, min_version):
    """Decorator raising SkipTest if the OS is `sysname` and the version is less
    than `min_version`.

    For example, @_requires_unix_version('FreeBSD', (7, 2)) raises SkipTest if
    the FreeBSD version is less than 7.2.
    """
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kw):
            if platform.system() == sysname:
                version_txt = platform.release().split('-', 1)[0]
                try:
                    version = tuple(map(int, version_txt.split('.')))
                except ValueError:
                    pass
                else:
                    if version < min_version:
                        min_version_txt = '.'.join(map(str, min_version))
                        raise unittest.SkipTest(
                            "%s version %s or higher required, not %s"
                            % (sysname, min_version_txt, version_txt))
        return wrapper
    return decorator

def requires_freebsd_version(*min_version):
    """Decorator raising SkipTest if the OS is FreeBSD and the FreeBSD version is
    less than `min_version`.

    For example, @requires_freebsd_version(7, 2) raises SkipTest if the FreeBSD
    version is less than 7.2.
    """
    return _requires_unix_version('FreeBSD', min_version)

def requires_linux_version(*min_version):
    """Decorator raising SkipTest if the OS is Linux and the Linux version is
    less than `min_version`.

    For example, @requires_linux_version(2, 6, 32) raises SkipTest if the Linux
    version is less than 2.6.32.
    """
    return _requires_unix_version('Linux', min_version)

def requires_mac_ver(*min_version):
    """Decorator raising SkipTest if the OS is Mac OS X and the OS X
    version if less than min_version.

    For example, @requires_mac_ver(10, 5) raises SkipTest if the OS X version
    is lesser than 10.5.
    """
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kw):
            if sys.platform == 'darwin':
                version_txt = platform.mac_ver()[0]
                try:
                    version = tuple(map(int, version_txt.split('.')))
                except ValueError:
                    pass
                else:
                    if version < min_version:
                        min_version_txt = '.'.join(map(str, min_version))
                        raise unittest.SkipTest(
                            "Mac OS X %s or higher required, not %s"
                            % (min_version_txt, version_txt))
            return func(*args, **kw)
        wrapper.min_version = min_version
        return wrapper
    return decorator


HOST = 'localhost'

def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM):
    """Returns an unused port that should be suitable for binding.  This is
    achieved by creating a temporary socket with the same family and type as
    the 'sock' parameter (default is AF_INET, SOCK_STREAM), and binding it to
    the specified host address (defaults to 0.0.0.0) with the port set to 0,
    eliciting an unused ephemeral port from the OS.  The temporary socket is
    then closed and deleted, and the ephemeral port is returned.

    Either this method or bind_port() should be used for any tests where a
    server socket needs to be bound to a particular port for the duration of
    the test.  Which one to use depends on whether the calling code is creating
    a python socket, or if an unused port needs to be provided in a constructor
    or passed to an external program (i.e. the -accept argument to openssl's
    s_server mode).  Always prefer bind_port() over find_unused_port() where
    possible.  Hard coded ports should *NEVER* be used.  As soon as a server
    socket is bound to a hard coded port, the ability to run multiple instances
    of the test simultaneously on the same host is compromised, which makes the
    test a ticking time bomb in a buildbot environment. On Unix buildbots, this
    may simply manifest as a failed test, which can be recovered from without
    intervention in most cases, but on Windows, the entire python process can
    completely and utterly wedge, requiring someone to log in to the buildbot
    and manually kill the affected process.

    (This is easy to reproduce on Windows, unfortunately, and can be traced to
    the SO_REUSEADDR socket option having different semantics on Windows versus
    Unix/Linux.  On Unix, you can't have two AF_INET SOCK_STREAM sockets bind,
    listen and then accept connections on identical host/ports.  An EADDRINUSE
    socket.error will be raised at some point (depending on the platform and
    the order bind and listen were called on each socket).

    However, on Windows, if SO_REUSEADDR is set on the sockets, no EADDRINUSE
    will ever be raised when attempting to bind two identical host/ports. When
    accept() is called on each socket, the second caller's process will steal
    the port from the first caller, leaving them both in an awkwardly wedged
    state where they'll no longer respond to any signals or graceful kills, and
    must be forcibly killed via OpenProcess()/TerminateProcess().

    The solution on Windows is to use the SO_EXCLUSIVEADDRUSE socket option
    instead of SO_REUSEADDR, which effectively affords the same semantics as
    SO_REUSEADDR on Unix.  Given the propensity of Unix developers in the Open
    Source world compared to Windows ones, this is a common mistake.  A quick
    look over OpenSSL's 0.9.8g source shows that they use SO_REUSEADDR when
    openssl.exe is called with the 's_server' option, for example. See
    http://bugs.python.org/issue2550 for more info.  The following site also
    has a very thorough description about the implications of both REUSEADDR
    and EXCLUSIVEADDRUSE on Windows:
    http://msdn2.microsoft.com/en-us/library/ms740621(VS.85).aspx)

    XXX: although this approach is a vast improvement on previous attempts to
    elicit unused ports, it rests heavily on the assumption that the ephemeral
    port returned to us by the OS won't immediately be dished back out to some
    other process when we close and delete our temporary socket but before our
    calling code has a chance to bind the returned port.  We can deal with this
    issue if/when we come across it.
    """

    tempsock = socket.socket(family, socktype)
    port = bind_port(tempsock)
    tempsock.close()
    del tempsock
    return port

def bind_port(sock, host=HOST):
    """Bind the socket to a free port and return the port number.  Relies on
    ephemeral ports in order to ensure we are using an unbound port.  This is
    important as many tests may be running simultaneously, especially in a
    buildbot environment.  This method raises an exception if the sock.family
    is AF_INET and sock.type is SOCK_STREAM, *and* the socket has SO_REUSEADDR
    or SO_REUSEPORT set on it.  Tests should *never* set these socket options
    for TCP/IP sockets.  The only case for setting these options is testing
    multicasting via multiple UDP sockets.

    Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e.
    on Windows), it will be set on the socket.  This will prevent anyone else
    from bind()'ing to our host/port for the duration of the test.
    """

    if sock.family == socket.AF_INET and sock.type == socket.SOCK_STREAM:
        if hasattr(socket, 'SO_REUSEADDR'):
            if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1:
                raise TestFailed("tests should never set the SO_REUSEADDR "   \
                                 "socket option on TCP/IP sockets!")
        if hasattr(socket, 'SO_REUSEPORT'):
            if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1:
                raise TestFailed("tests should never set the SO_REUSEPORT "   \
                                 "socket option on TCP/IP sockets!")
        if hasattr(socket, 'SO_EXCLUSIVEADDRUSE'):
            sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)

    sock.bind((host, 0))
    port = sock.getsockname()[1]
    return port

def _is_ipv6_enabled():
    """Check whether IPv6 is enabled on this host."""
    if socket.has_ipv6:
        sock = None
        try:
            sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
            sock.bind(('::1', 0))
            return True
        except (socket.error, socket.gaierror):
            pass
        finally:
            if sock:
                sock.close()
    return False

IPV6_ENABLED = _is_ipv6_enabled()


# A constant likely larger than the underlying OS pipe buffer size.
# Windows limit seems to be around 512B, and most Unix kernels have a 64K pipe
# buffer size: take 1M to be sure.
PIPE_MAX_SIZE = 1024 * 1024


# decorator for skipping tests on non-IEEE 754 platforms
requires_IEEE_754 = unittest.skipUnless(
    float.__getformat__("double").startswith("IEEE"),
    "test requires IEEE 754 doubles")

requires_zlib = unittest.skipUnless(zlib, 'requires zlib')

requires_bz2 = unittest.skipUnless(bz2, 'requires bz2')

requires_lzma = unittest.skipUnless(lzma, 'requires lzma')

is_jython = sys.platform.startswith('java')

# Filename used for testing
if os.name == 'java':
    # Jython disallows @ in module names
    TESTFN = '$test'
else:
    TESTFN = '@test'

# Disambiguate TESTFN for parallel testing, while letting it remain a valid
# module name.
TESTFN = "{}_{}_tmp".format(TESTFN, os.getpid())

# FS_NONASCII: non-ASCII character encodable by os.fsencode(),
# or None if there is no such character.
FS_NONASCII = None
for character in (
    # First try printable and common characters to have a readable filename.
    # For each character, the encoding list are just example of encodings able
    # to encode the character (the list is not exhaustive).

    # U+00E6 (Latin Small Letter Ae): cp1252, iso-8859-1
    '\u00E6',
    # U+0130 (Latin Capital Letter I With Dot Above): cp1254, iso8859_3
    '\u0130',
    # U+0141 (Latin Capital Letter L With Stroke): cp1250, cp1257
    '\u0141',
    # U+03C6 (Greek Small Letter Phi): cp1253
    '\u03C6',
    # U+041A (Cyrillic Capital Letter Ka): cp1251
    '\u041A',
    # U+05D0 (Hebrew Letter Alef): Encodable to cp424
    '\u05D0',
    # U+060C (Arabic Comma): cp864, cp1006, iso8859_6, mac_arabic
    '\u060C',
    # U+062A (Arabic Letter Teh): cp720
    '\u062A',
    # U+0E01 (Thai Character Ko Kai): cp874
    '\u0E01',

    # Then try more "special" characters. "special" because they may be
    # interpreted or displayed differently depending on the exact locale
    # encoding and the font.

    # U+00A0 (No-Break Space)
    '\u00A0',
    # U+20AC (Euro Sign)
    '\u20AC',
):
    try:
        os.fsdecode(os.fsencode(character))
    except UnicodeError:
        pass
    else:
        FS_NONASCII = character
        break

# TESTFN_UNICODE is a non-ascii filename
TESTFN_UNICODE = TESTFN + "-\xe0\xf2\u0258\u0141\u011f"
if sys.platform == 'darwin':
    # In Mac OS X's VFS API file names are, by definition, canonically
    # decomposed Unicode, encoded using UTF-8. See QA1173:
    # http://developer.apple.com/mac/library/qa/qa2001/qa1173.html
    import unicodedata
    TESTFN_UNICODE = unicodedata.normalize('NFD', TESTFN_UNICODE)
TESTFN_ENCODING = sys.getfilesystemencoding()

# TESTFN_UNENCODABLE is a filename (str type) that should *not* be able to be
# encoded by the filesystem encoding (in strict mode). It can be None if we
# cannot generate such filename.
TESTFN_UNENCODABLE = None
if os.name in ('nt', 'ce'):
    # skip win32s (0) or Windows 9x/ME (1)
    if sys.getwindowsversion().platform >= 2:
        # Different kinds of characters from various languages to minimize the
        # probability that the whole name is encodable to MBCS (issue #9819)
        TESTFN_UNENCODABLE = TESTFN + "-\u5171\u0141\u2661\u0363\uDC80"
        try:
            TESTFN_UNENCODABLE.encode(TESTFN_ENCODING)
        except UnicodeEncodeError:
            pass
        else:
            print('WARNING: The filename %r CAN be encoded by the filesystem encoding (%s). '
                  'Unicode filename tests may not be effective'
                  % (TESTFN_UNENCODABLE, TESTFN_ENCODING))
            TESTFN_UNENCODABLE = None
# Mac OS X denies unencodable filenames (invalid utf-8)
elif sys.platform != 'darwin':
    try:
        # ascii and utf-8 cannot encode the byte 0xff
        b'\xff'.decode(TESTFN_ENCODING)
    except UnicodeDecodeError:
        # 0xff will be encoded using the surrogate character u+DCFF
        TESTFN_UNENCODABLE = TESTFN \
            + b'-\xff'.decode(TESTFN_ENCODING, 'surrogateescape')
    else:
        # File system encoding (eg. ISO-8859-* encodings) can encode
        # the byte 0xff. Skip some unicode filename tests.
        pass

# TESTFN_UNDECODABLE is a filename (bytes type) that should *not* be able to be
# decoded from the filesystem encoding (in strict mode). It can be None if we
# cannot generate such filename (ex: the latin1 encoding can decode any byte
# sequence). On UNIX, TESTFN_UNDECODABLE can be decoded by os.fsdecode() thanks
# to the surrogateescape error handler (PEP 383), but not from the filesystem
# encoding in strict mode.
TESTFN_UNDECODABLE = None
for name in (
    # b'\xff' is not decodable by os.fsdecode() with code page 932. Windows
    # accepts it to create a file or a directory, or don't accept to enter to
    # such directory (when the bytes name is used). So test b'\xe7' first: it is
    # not decodable from cp932.
    b'\xe7w\xf0',
    # undecodable from ASCII, UTF-8
    b'\xff',
    # undecodable from iso8859-3, iso8859-6, iso8859-7, cp424, iso8859-8, cp856
    # and cp857
    b'\xae\xd5'
    # undecodable from UTF-8 (UNIX and Mac OS X)
    b'\xed\xb2\x80', b'\xed\xb4\x80',
):
    try:
        name.decode(TESTFN_ENCODING)
    except UnicodeDecodeError:
        TESTFN_UNDECODABLE = os.fsencode(TESTFN) + name
        break

if FS_NONASCII:
    TESTFN_NONASCII = TESTFN + '-' + FS_NONASCII
else:
    TESTFN_NONASCII = None

# Save the initial cwd
SAVEDCWD = os.getcwd()

@contextlib.contextmanager
def temp_cwd(name='tempcwd', quiet=False, path=None):
    """
    Context manager that temporarily changes the CWD.

    An existing path may be provided as *path*, in which case this
    function makes no changes to the file system.

    Otherwise, the new CWD is created in the current directory and it's
    named *name*. If *quiet* is False (default) and it's not possible to
    create or change the CWD, an error is raised.  If it's True, only a
    warning is raised and the original CWD is used.
    """
    saved_dir = os.getcwd()
    is_temporary = False
    if path is None:
        path = name
        try:
            os.mkdir(name)
            is_temporary = True
        except OSError:
            if not quiet:
                raise
            warnings.warn('tests may fail, unable to create temp CWD ' + name,
                          RuntimeWarning, stacklevel=3)
    try:
        os.chdir(path)
    except OSError:
        if not quiet:
            raise
        warnings.warn('tests may fail, unable to change the CWD to ' + path,
                      RuntimeWarning, stacklevel=3)
    try:
        yield os.getcwd()
    finally:
        os.chdir(saved_dir)
        if is_temporary:
            rmtree(name)


if hasattr(os, "umask"):
    @contextlib.contextmanager
    def temp_umask(umask):
        """Context manager that temporarily sets the process umask."""
        oldmask = os.umask(umask)
        try:
            yield
        finally:
            os.umask(oldmask)


def findfile(file, here=__file__, subdir=None):
    """Try to find a file on sys.path and the working directory.  If it is not
    found the argument passed to the function is returned (this does not
    necessarily signal failure; could still be the legitimate path)."""
    if os.path.isabs(file):
        return file
    if subdir is not None:
        file = os.path.join(subdir, file)
    path = sys.path
    path = [os.path.dirname(here)] + path
    for dn in path:
        fn = os.path.join(dn, file)
        if os.path.exists(fn): return fn
    return file

def create_empty_file(filename):
    """Create an empty file. If the file already exists, truncate it."""
    fd = os.open(filename, os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
    os.close(fd)

def sortdict(dict):
    "Like repr(dict), but in sorted order."
    items = sorted(dict.items())
    reprpairs = ["%r: %r" % pair for pair in items]
    withcommas = ", ".join(reprpairs)
    return "{%s}" % withcommas

def make_bad_fd():
    """
    Create an invalid file descriptor by opening and closing a file and return
    its fd.
    """
    file = open(TESTFN, "wb")
    try:
        return file.fileno()
    finally:
        file.close()
        unlink(TESTFN)

def check_syntax_error(testcase, statement):
    testcase.assertRaises(SyntaxError, compile, statement,
                          '<test string>', 'exec')

def open_urlresource(url, *args, **kw):
    import urllib.request, urllib.parse

    check = kw.pop('check', None)

    filename = urllib.parse.urlparse(url)[2].split('/')[-1] # '/': it's URL!

    fn = os.path.join(os.path.dirname(__file__), "data", filename)

    def check_valid_file(fn):
        f = open(fn, *args, **kw)
        if check is None:
            return f
        elif check(f):
            f.seek(0)
            return f
        f.close()

    if os.path.exists(fn):
        f = check_valid_file(fn)
        if f is not None:
            return f
        unlink(fn)

    # Verify the requirement before downloading the file
    requires('urlfetch')

    print('\tfetching %s ...' % url, file=get_original_stdout())
    f = urllib.request.urlopen(url, timeout=15)
    try:
        with open(fn, "wb") as out:
            s = f.read()
            while s:
                out.write(s)
                s = f.read()
    finally:
        f.close()

    f = check_valid_file(fn)
    if f is not None:
        return f
    raise TestFailed('invalid resource %r' % fn)


class WarningsRecorder(object):
    """Convenience wrapper for the warnings list returned on
       entry to the warnings.catch_warnings() context manager.
    """
    def __init__(self, warnings_list):
        self._warnings = warnings_list
        self._last = 0

    def __getattr__(self, attr):
        if len(self._warnings) > self._last:
            return getattr(self._warnings[-1], attr)
        elif attr in warnings.WarningMessage._WARNING_DETAILS:
            return None
        raise AttributeError("%r has no attribute %r" % (self, attr))

    @property
    def warnings(self):
        return self._warnings[self._last:]

    def reset(self):
        self._last = len(self._warnings)


def _filterwarnings(filters, quiet=False):
    """Catch the warnings, then check if all the expected
    warnings have been raised and re-raise unexpected warnings.
    If 'quiet' is True, only re-raise the unexpected warnings.
    """
    # Clear the warning registry of the calling module
    # in order to re-raise the warnings.
    frame = sys._getframe(2)
    registry = frame.f_globals.get('__warningregistry__')
    if registry:
        registry.clear()
    with warnings.catch_warnings(record=True) as w:
        # Set filter "always" to record all warnings.  Because
        # test_warnings swap the module, we need to look up in
        # the sys.modules dictionary.
        sys.modules['warnings'].simplefilter("always")
        yield WarningsRecorder(w)
    # Filter the recorded warnings
    reraise = list(w)
    missing = []
    for msg, cat in filters:
        seen = False
        for w in reraise[:]:
            warning = w.message
            # Filter out the matching messages
            if (re.match(msg, str(warning), re.I) and
                issubclass(warning.__class__, cat)):
                seen = True
                reraise.remove(w)
        if not seen and not quiet:
            # This filter caught nothing
            missing.append((msg, cat.__name__))
    if reraise:
        raise AssertionError("unhandled warning %s" % reraise[0])
    if missing:
        raise AssertionError("filter (%r, %s) did not catch any warning" %
                             missing[0])


@contextlib.contextmanager
def check_warnings(*filters, **kwargs):
    """Context manager to silence warnings.

    Accept 2-tuples as positional arguments:
        ("message regexp", WarningCategory)

    Optional argument:
     - if 'quiet' is True, it does not fail if a filter catches nothing
        (default True without argument,
         default False if some filters are defined)

    Without argument, it defaults to:
        check_warnings(("", Warning), quiet=True)
    """
    quiet = kwargs.get('quiet')
    if not filters:
        filters = (("", Warning),)
        # Preserve backward compatibility
        if quiet is None:
            quiet = True
    return _filterwarnings(filters, quiet)


class CleanImport(object):
    """Context manager to force import to return a new module reference.

    This is useful for testing module-level behaviours, such as
    the emission of a DeprecationWarning on import.

    Use like this:

        with CleanImport("foo"):
            importlib.import_module("foo") # new reference
    """

    def __init__(self, *module_names):
        self.original_modules = sys.modules.copy()
        for module_name in module_names:
            if module_name in sys.modules:
                module = sys.modules[module_name]
                # It is possible that module_name is just an alias for
                # another module (e.g. stub for modules renamed in 3.x).
                # In that case, we also need delete the real module to clear
                # the import cache.
                if module.__name__ != module_name:
                    del sys.modules[module.__name__]
                del sys.modules[module_name]

    def __enter__(self):
        return self

    def __exit__(self, *ignore_exc):
        sys.modules.update(self.original_modules)


class EnvironmentVarGuard(collections.abc.MutableMapping):

    """Class to help protect the environment variable properly.  Can be used as
    a context manager."""

    def __init__(self):
        self._environ = os.environ
        self._changed = {}

    def __getitem__(self, envvar):
        return self._environ[envvar]

    def __setitem__(self, envvar, value):
        # Remember the initial value on the first access
        if envvar not in self._changed:
            self._changed[envvar] = self._environ.get(envvar)
        self._environ[envvar] = value

    def __delitem__(self, envvar):
        # Remember the initial value on the first access
        if envvar not in self._changed:
            self._changed[envvar] = self._environ.get(envvar)
        if envvar in self._environ:
            del self._environ[envvar]

    def keys(self):
        return self._environ.keys()

    def __iter__(self):
        return iter(self._environ)

    def __len__(self):
        return len(self._environ)

    def set(self, envvar, value):
        self[envvar] = value

    def unset(self, envvar):
        del self[envvar]

    def __enter__(self):
        return self

    def __exit__(self, *ignore_exc):
        for (k, v) in self._changed.items():
            if v is None:
                if k in self._environ:
                    del self._environ[k]
            else:
                self._environ[k] = v
        os.environ = self._environ


class DirsOnSysPath(object):
    """Context manager to temporarily add directories to sys.path.

    This makes a copy of sys.path, appends any directories given
    as positional arguments, then reverts sys.path to the copied
    settings when the context ends.

    Note that *all* sys.path modifications in the body of the
    context manager, including replacement of the object,
    will be reverted at the end of the block.
    """

    def __init__(self, *paths):
        self.original_value = sys.path[:]
        self.original_object = sys.path
        sys.path.extend(paths)

    def __enter__(self):
        return self

    def __exit__(self, *ignore_exc):
        sys.path = self.original_object
        sys.path[:] = self.original_value


class TransientResource(object):

    """Raise ResourceDenied if an exception is raised while the context manager
    is in effect that matches the specified exception and attributes."""

    def __init__(self, exc, **kwargs):
        self.exc = exc
        self.attrs = kwargs

    def __enter__(self):
        return self

    def __exit__(self, type_=None, value=None, traceback=None):
        """If type_ is a subclass of self.exc and value has attributes matching


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