Don't link file again if it's already a correct hard link

Closes gh-6450

IPython/utils/path.py

@@ -1,587 +1,593 b''
 # encoding: utf-8
 """
 Utilities for path handling.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import os
 import sys
 import errno
 import shutil
 import random
 import tempfile
 import glob
 from warnings import warn
 from hashlib import md5
 
 import IPython
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils.process import system
 from IPython.utils.importstring import import_item
 from IPython.utils import py3compat
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
 fs_encoding = sys.getfilesystemencoding()
 
 def _writable_dir(path):
     """Whether `path` is a directory, to which the user has write access."""
     return os.path.isdir(path) and os.access(path, os.W_OK)
 
 if sys.platform == 'win32':
     @skip_doctest
     def _get_long_path_name(path):
         """Get a long path name (expand ~) on Windows using ctypes.
 
         Examples
         --------
 
         >>> get_long_path_name('c:\\docume~1')
         u'c:\\\\Documents and Settings'
 
         """
         try:
             import ctypes
         except ImportError:
             raise ImportError('you need to have ctypes installed for this to work')
         _GetLongPathName = ctypes.windll.kernel32.GetLongPathNameW
         _GetLongPathName.argtypes = [ctypes.c_wchar_p, ctypes.c_wchar_p,
             ctypes.c_uint ]
 
         buf = ctypes.create_unicode_buffer(260)
         rv = _GetLongPathName(path, buf, 260)
         if rv == 0 or rv > 260:
             return path
         else:
             return buf.value
 else:
     def _get_long_path_name(path):
         """Dummy no-op."""
         return path
 
 
 
 def get_long_path_name(path):
     """Expand a path into its long form.
 
     On Windows this expands any ~ in the paths. On other platforms, it is
     a null operation.
     """
     return _get_long_path_name(path)
 
 
 def unquote_filename(name, win32=(sys.platform=='win32')):
     """ On Windows, remove leading and trailing quotes from filenames.
     """
     if win32:
         if name.startswith(("'", '"')) and name.endswith(("'", '"')):
             name = name[1:-1]
     return name
 
 def compress_user(path):
     """Reverse of :func:`os.path.expanduser`
     """
     home = os.path.expanduser('~')
     if path.startswith(home):
         path =  "~" + path[len(home):]
     return path
 
 def get_py_filename(name, force_win32=None):
     """Return a valid python filename in the current directory.
 
     If the given name is not a file, it adds '.py' and searches again.
     Raises IOError with an informative message if the file isn't found.
 
     On Windows, apply Windows semantics to the filename. In particular, remove
     any quoting that has been applied to it. This option can be forced for
     testing purposes.
     """
 
     name = os.path.expanduser(name)
     if force_win32 is None:
         win32 = (sys.platform == 'win32')
     else:
         win32 = force_win32
     name = unquote_filename(name, win32=win32)
     if not os.path.isfile(name) and not name.endswith('.py'):
         name += '.py'
     if os.path.isfile(name):
         return name
     else:
         raise IOError('File `%r` not found.' % name)
 
 
 def filefind(filename, path_dirs=None):
     """Find a file by looking through a sequence of paths.
 
     This iterates through a sequence of paths looking for a file and returns
     the full, absolute path of the first occurence of the file.  If no set of
     path dirs is given, the filename is tested as is, after running through
     :func:`expandvars` and :func:`expanduser`.  Thus a simple call::
 
         filefind('myfile.txt')
 
     will find the file in the current working dir, but::
 
         filefind('~/myfile.txt')
 
     Will find the file in the users home directory.  This function does not
     automatically try any paths, such as the cwd or the user's home directory.
 
     Parameters
     ----------
     filename : str
         The filename to look for.
     path_dirs : str, None or sequence of str
         The sequence of paths to look for the file in.  If None, the filename
         need to be absolute or be in the cwd.  If a string, the string is
         put into a sequence and the searched.  If a sequence, walk through
         each element and join with ``filename``, calling :func:`expandvars`
         and :func:`expanduser` before testing for existence.
 
     Returns
     -------
     Raises :exc:`IOError` or returns absolute path to file.
     """
 
     # If paths are quoted, abspath gets confused, strip them...
     filename = filename.strip('"').strip("'")
     # If the input is an absolute path, just check it exists
     if os.path.isabs(filename) and os.path.isfile(filename):
         return filename
 
     if path_dirs is None:
         path_dirs = ("",)
     elif isinstance(path_dirs, py3compat.string_types):
         path_dirs = (path_dirs,)
 
     for path in path_dirs:
         if path == '.': path = py3compat.getcwd()
         testname = expand_path(os.path.join(path, filename))
         if os.path.isfile(testname):
             return os.path.abspath(testname)
 
     raise IOError("File %r does not exist in any of the search paths: %r" %
                   (filename, path_dirs) )
 
 
 class HomeDirError(Exception):
     pass
 
 
 def get_home_dir(require_writable=False):
     """Return the 'home' directory, as a unicode string.
 
     Uses os.path.expanduser('~'), and checks for writability.
     
     See stdlib docs for how this is determined.
     $HOME is first priority on *ALL* platforms.
     
     Parameters
     ----------
     
     require_writable : bool [default: False]
         if True:
             guarantees the return value is a writable directory, otherwise
             raises HomeDirError
         if False:
             The path is resolved, but it is not guaranteed to exist or be writable.
     """
 
     homedir = os.path.expanduser('~')
     # Next line will make things work even when /home/ is a symlink to
     # /usr/home as it is on FreeBSD, for example
     homedir = os.path.realpath(homedir)
     
     if not _writable_dir(homedir) and os.name == 'nt':
         # expanduser failed, use the registry to get the 'My Documents' folder.
         try:
             try:
                 import winreg as wreg  # Py 3
             except ImportError:
                 import _winreg as wreg  # Py 2
             key = wreg.OpenKey(
                 wreg.HKEY_CURRENT_USER,
                 "Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders"
             )
             homedir = wreg.QueryValueEx(key,'Personal')[0]
             key.Close()
         except:
             pass
     
     if (not require_writable) or _writable_dir(homedir):
         return py3compat.cast_unicode(homedir, fs_encoding)
     else:
         raise HomeDirError('%s is not a writable dir, '
                 'set $HOME environment variable to override' % homedir)
 
 def get_xdg_dir():
     """Return the XDG_CONFIG_HOME, if it is defined and exists, else None.
 
     This is only for non-OS X posix (Linux,Unix,etc.) systems.
     """
 
     env = os.environ
 
     if os.name == 'posix' and sys.platform != 'darwin':
         # Linux, Unix, AIX, etc.
         # use ~/.config if empty OR not set
         xdg = env.get("XDG_CONFIG_HOME", None) or os.path.join(get_home_dir(), '.config')
         if xdg and _writable_dir(xdg):
             return py3compat.cast_unicode(xdg, fs_encoding)
 
     return None
 
 
 def get_xdg_cache_dir():
     """Return the XDG_CACHE_HOME, if it is defined and exists, else None.
 
     This is only for non-OS X posix (Linux,Unix,etc.) systems.
     """
 
     env = os.environ
 
     if os.name == 'posix' and sys.platform != 'darwin':
         # Linux, Unix, AIX, etc.
         # use ~/.cache if empty OR not set
         xdg = env.get("XDG_CACHE_HOME", None) or os.path.join(get_home_dir(), '.cache')
         if xdg and _writable_dir(xdg):
             return py3compat.cast_unicode(xdg, fs_encoding)
 
     return None
 
 
 def get_ipython_dir():
     """Get the IPython directory for this platform and user.
 
     This uses the logic in `get_home_dir` to find the home directory
     and then adds .ipython to the end of the path.
     """
 
     env = os.environ
     pjoin = os.path.join
 
 
     ipdir_def = '.ipython'
 
     home_dir = get_home_dir()
     xdg_dir = get_xdg_dir()
     
     # import pdb; pdb.set_trace()  # dbg
     if 'IPYTHON_DIR' in env:
         warn('The environment variable IPYTHON_DIR is deprecated. '
                 'Please use IPYTHONDIR instead.')
     ipdir = env.get('IPYTHONDIR', env.get('IPYTHON_DIR', None))
     if ipdir is None:
         # not set explicitly, use ~/.ipython
         ipdir = pjoin(home_dir, ipdir_def)
         if xdg_dir:
             # Several IPython versions (up to 1.x) defaulted to .config/ipython
             # on Linux. We have decided to go back to using .ipython everywhere
             xdg_ipdir = pjoin(xdg_dir, 'ipython')
 
             if _writable_dir(xdg_ipdir):
                 cu = compress_user
                 if os.path.exists(ipdir):
                     warn(('Ignoring {0} in favour of {1}. Remove {0} to '
                         'get rid of this message').format(cu(xdg_ipdir), cu(ipdir)))
                 elif os.path.islink(xdg_ipdir):
                     warn(('{0} is deprecated. Move link to {1} to '
                         'get rid of this message').format(cu(xdg_ipdir), cu(ipdir)))
                 else:
                     warn('Moving {0} to {1}'.format(cu(xdg_ipdir), cu(ipdir)))
                     shutil.move(xdg_ipdir, ipdir)
 
     ipdir = os.path.normpath(os.path.expanduser(ipdir))
 
     if os.path.exists(ipdir) and not _writable_dir(ipdir):
         # ipdir exists, but is not writable
         warn("IPython dir '{0}' is not a writable location,"
                 " using a temp directory.".format(ipdir))
         ipdir = tempfile.mkdtemp()
     elif not os.path.exists(ipdir):
         parent = os.path.dirname(ipdir)
         if not _writable_dir(parent):
             # ipdir does not exist and parent isn't writable
             warn("IPython parent '{0}' is not a writable location,"
                     " using a temp directory.".format(parent))
             ipdir = tempfile.mkdtemp()
 
     return py3compat.cast_unicode(ipdir, fs_encoding)
 
 
 def get_ipython_cache_dir():
     """Get the cache directory it is created if it does not exist."""
     xdgdir = get_xdg_cache_dir()
     if xdgdir is None:
         return get_ipython_dir()
     ipdir = os.path.join(xdgdir, "ipython")
     if not os.path.exists(ipdir) and _writable_dir(xdgdir):
         ensure_dir_exists(ipdir)
     elif not _writable_dir(xdgdir):
         return get_ipython_dir()
 
     return py3compat.cast_unicode(ipdir, fs_encoding)
 
 
 def get_ipython_package_dir():
     """Get the base directory where IPython itself is installed."""
     ipdir = os.path.dirname(IPython.__file__)
     return py3compat.cast_unicode(ipdir, fs_encoding)
 
 
 def get_ipython_module_path(module_str):
     """Find the path to an IPython module in this version of IPython.
 
     This will always find the version of the module that is in this importable
     IPython package. This will always return the path to the ``.py``
     version of the module.
     """
     if module_str == 'IPython':
         return os.path.join(get_ipython_package_dir(), '__init__.py')
     mod = import_item(module_str)
     the_path = mod.__file__.replace('.pyc', '.py')
     the_path = the_path.replace('.pyo', '.py')
     return py3compat.cast_unicode(the_path, fs_encoding)
 
 def locate_profile(profile='default'):
     """Find the path to the folder associated with a given profile.
     
     I.e. find $IPYTHONDIR/profile_whatever.
     """
     from IPython.core.profiledir import ProfileDir, ProfileDirError
     try:
         pd = ProfileDir.find_profile_dir_by_name(get_ipython_dir(), profile)
     except ProfileDirError:
         # IOError makes more sense when people are expecting a path
         raise IOError("Couldn't find profile %r" % profile)
     return pd.location
 
 def expand_path(s):
     """Expand $VARS and ~names in a string, like a shell
 
     :Examples:
 
        In [2]: os.environ['FOO']='test'
 
        In [3]: expand_path('variable FOO is $FOO')
        Out[3]: 'variable FOO is test'
     """
     # This is a pretty subtle hack. When expand user is given a UNC path
     # on Windows (\\server\share$\%username%), os.path.expandvars, removes
     # the $ to get (\\server\share\%username%). I think it considered $
     # alone an empty var. But, we need the $ to remains there (it indicates
     # a hidden share).
     if os.name=='nt':
         s = s.replace('$\\', 'IPYTHON_TEMP')
     s = os.path.expandvars(os.path.expanduser(s))
     if os.name=='nt':
         s = s.replace('IPYTHON_TEMP', '$\\')
     return s
 
 
 def unescape_glob(string):
     """Unescape glob pattern in `string`."""
     def unescape(s):
         for pattern in '*[]!?':
             s = s.replace(r'\{0}'.format(pattern), pattern)
         return s
     return '\\'.join(map(unescape, string.split('\\\\')))
 
 
 def shellglob(args):
     """
     Do glob expansion for each element in `args` and return a flattened list.
 
     Unmatched glob pattern will remain as-is in the returned list.
 
     """
     expanded = []
     # Do not unescape backslash in Windows as it is interpreted as
     # path separator:
     unescape = unescape_glob if sys.platform != 'win32' else lambda x: x
     for a in args:
         expanded.extend(glob.glob(a) or [unescape(a)])
     return expanded
 
 
 def target_outdated(target,deps):
     """Determine whether a target is out of date.
 
     target_outdated(target,deps) -> 1/0
 
     deps: list of filenames which MUST exist.
     target: single filename which may or may not exist.
 
     If target doesn't exist or is older than any file listed in deps, return
     true, otherwise return false.
     """
     try:
         target_time = os.path.getmtime(target)
     except os.error:
         return 1
     for dep in deps:
         dep_time = os.path.getmtime(dep)
         if dep_time > target_time:
             #print "For target",target,"Dep failed:",dep # dbg
             #print "times (dep,tar):",dep_time,target_time # dbg
             return 1
     return 0
 
 
 def target_update(target,deps,cmd):
     """Update a target with a given command given a list of dependencies.
 
     target_update(target,deps,cmd) -> runs cmd if target is outdated.
 
     This is just a wrapper around target_outdated() which calls the given
     command if target is outdated."""
 
     if target_outdated(target,deps):
         system(cmd)
 
 def filehash(path):
     """Make an MD5 hash of a file, ignoring any differences in line
     ending characters."""
     with open(path, "rU") as f:
         return md5(py3compat.str_to_bytes(f.read())).hexdigest()
 
 # If the config is unmodified from the default, we'll just delete it.
 # These are consistent for 0.10.x, thankfully. We're not going to worry about
 # older versions.
 old_config_md5 = {'ipy_user_conf.py': 'fc108bedff4b9a00f91fa0a5999140d3',
                   'ipythonrc': '12a68954f3403eea2eec09dc8fe5a9b5'}
 
 def check_for_old_config(ipython_dir=None):
     """Check for old config files, and present a warning if they exist.
 
     A link to the docs of the new config is included in the message.
 
     This should mitigate confusion with the transition to the new
     config system in 0.11.
     """
     if ipython_dir is None:
         ipython_dir = get_ipython_dir()
 
     old_configs = ['ipy_user_conf.py', 'ipythonrc', 'ipython_config.py']
     warned = False
     for cfg in old_configs:
         f = os.path.join(ipython_dir, cfg)
         if os.path.exists(f):
             if filehash(f) == old_config_md5.get(cfg, ''):
                 os.unlink(f)
             else:
                 warn("Found old IPython config file {!r} (modified by user)".format(f))
                 warned = True
 
     if warned:
         warn("""
   The IPython configuration system has changed as of 0.11, and these files will
   be ignored. See http://ipython.github.com/ipython-doc/dev/config for details
   of the new config system.
   To start configuring IPython, do `ipython profile create`, and edit
   `ipython_config.py` in <ipython_dir>/profile_default.
   If you need to leave the old config files in place for an older version of
   IPython and want to suppress this warning message, set
   `c.InteractiveShellApp.ignore_old_config=True` in the new config.""")
 
 def get_security_file(filename, profile='default'):
     """Return the absolute path of a security file given by filename and profile
     
     This allows users and developers to find security files without
     knowledge of the IPython directory structure. The search path
     will be ['.', profile.security_dir]
     
     Parameters
     ----------
     
     filename : str
         The file to be found. If it is passed as an absolute path, it will
         simply be returned.
     profile : str [default: 'default']
         The name of the profile to search.  Leaving this unspecified
         The file to be found. If it is passed as an absolute path, fname will
         simply be returned.
     
     Returns
     -------
     Raises :exc:`IOError` if file not found or returns absolute path to file.
     """
     # import here, because profiledir also imports from utils.path
     from IPython.core.profiledir import ProfileDir
     try:
         pd = ProfileDir.find_profile_dir_by_name(get_ipython_dir(), profile)
     except Exception:
         # will raise ProfileDirError if no such profile
         raise IOError("Profile %r not found")
     return filefind(filename, ['.', pd.security_dir])
 
 
 ENOLINK = 1998
 
 def link(src, dst):
     """Hard links ``src`` to ``dst``, returning 0 or errno.
 
     Note that the special errno ``ENOLINK`` will be returned if ``os.link`` isn't
     supported by the operating system.
     """
 
     if not hasattr(os, "link"):
         return ENOLINK
     link_errno = 0
     try:
         os.link(src, dst)
     except OSError as e:
         link_errno = e.errno
     return link_errno
 
 
 def link_or_copy(src, dst):
     """Attempts to hardlink ``src`` to ``dst``, copying if the link fails.
 
     Attempts to maintain the semantics of ``shutil.copy``.
 
     Because ``os.link`` does not overwrite files, a unique temporary file
     will be used if the target already exists, then that file will be moved
     into place.
     """
 
     if os.path.isdir(dst):
         dst = os.path.join(dst, os.path.basename(src))
 
     link_errno = link(src, dst)
     if link_errno == errno.EEXIST:
+        if os.stat(src).st_ino == os.stat(dst).st_ino:
+            # dst is already a hard link to the correct file, so we don't need
+            # to do anything else. If we try to link and rename the file
+            # anyway, we get duplicate files - see http://bugs.python.org/issue21876
+            return
+
         new_dst = dst + "-temp-%04X" %(random.randint(1, 16**4), )
         try:
             link_or_copy(src, new_dst)
         except:
             try:
                 os.remove(new_dst)
             except OSError:
                 pass
             raise
         os.rename(new_dst, dst)
     elif link_errno != 0:
         # Either link isn't supported, or the filesystem doesn't support
         # linking, or 'src' and 'dst' are on different filesystems.
         shutil.copy(src, dst)
 
 def ensure_dir_exists(path, mode=0o755):
     """ensure that a directory exists
     
     If it doesn't exist, try to create it and protect against a race condition
     if another process is doing the same.
     
     The default permissions are 755, which differ from os.makedirs default of 777.
     """
     if not os.path.exists(path):
         try:
             os.makedirs(path, mode=mode)
         except OSError as e:
             if e.errno != errno.EEXIST:
                 raise
     elif not os.path.isdir(path):
         raise IOError("%r exists but is not a directory" % path)

IPython/utils/tests/test_path.py

@@ -1,678 +1,687 b''
 # encoding: utf-8
 """Tests for IPython.utils.path.py"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import errno
 import os
 import shutil
 import sys
 import tempfile
 import warnings
 from contextlib import contextmanager
 
 try:  # Python 3.3+
     from unittest.mock import patch
 except ImportError:
     from mock import patch
 
 from os.path import join, abspath, split
 
 from nose import SkipTest
 import nose.tools as nt
 
 from nose import with_setup
 
 import IPython
 from IPython.testing import decorators as dec
 from IPython.testing.decorators import (skip_if_not_win32, skip_win32,
                                         onlyif_unicode_paths,)
 from IPython.testing.tools import make_tempfile, AssertPrints
 from IPython.utils import path
 from IPython.utils import py3compat
 from IPython.utils.tempdir import TemporaryDirectory
 
 # Platform-dependent imports
 try:
     import winreg as wreg  # Py 3
 except ImportError:
     try:
         import _winreg as wreg  # Py 2
     except ImportError:
         #Fake _winreg module on none windows platforms
         import types
         wr_name = "winreg" if py3compat.PY3 else "_winreg"
         sys.modules[wr_name] = types.ModuleType(wr_name)
         try:
             import winreg as wreg
         except ImportError:
             import _winreg as wreg
         #Add entries that needs to be stubbed by the testing code
         (wreg.OpenKey, wreg.QueryValueEx,) = (None, None)
 
 try:
     reload
 except NameError:   # Python 3
     from imp import reload
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 env = os.environ
 TEST_FILE_PATH = split(abspath(__file__))[0]
 TMP_TEST_DIR = tempfile.mkdtemp()
 HOME_TEST_DIR = join(TMP_TEST_DIR, "home_test_dir")
 XDG_TEST_DIR = join(HOME_TEST_DIR, "xdg_test_dir")
 XDG_CACHE_DIR = join(HOME_TEST_DIR, "xdg_cache_dir")
 IP_TEST_DIR = join(HOME_TEST_DIR,'.ipython')
 #
 # Setup/teardown functions/decorators
 #
 
 def setup():
     """Setup testenvironment for the module:
 
             - Adds dummy home dir tree
     """
     # Do not mask exceptions here.  In particular, catching WindowsError is a
     # problem because that exception is only defined on Windows...
     os.makedirs(IP_TEST_DIR)
     os.makedirs(os.path.join(XDG_TEST_DIR, 'ipython'))
     os.makedirs(os.path.join(XDG_CACHE_DIR, 'ipython'))
 
 
 def teardown():
     """Teardown testenvironment for the module:
 
             - Remove dummy home dir tree
     """
     # Note: we remove the parent test dir, which is the root of all test
     # subdirs we may have created.  Use shutil instead of os.removedirs, so
     # that non-empty directories are all recursively removed.
     shutil.rmtree(TMP_TEST_DIR)
 
 
 def setup_environment():
     """Setup testenvironment for some functions that are tested
     in this module. In particular this functions stores attributes
     and other things that we need to stub in some test functions.
     This needs to be done on a function level and not module level because
     each testfunction needs a pristine environment.
     """
     global oldstuff, platformstuff
     oldstuff = (env.copy(), os.name, sys.platform, path.get_home_dir, IPython.__file__, os.getcwd())
 
 def teardown_environment():
     """Restore things that were remembered by the setup_environment function
     """
     (oldenv, os.name, sys.platform, path.get_home_dir, IPython.__file__, old_wd) = oldstuff
     os.chdir(old_wd)
     reload(path)
 
     for key in list(env):
         if key not in oldenv:
             del env[key]
     env.update(oldenv)
     if hasattr(sys, 'frozen'):
         del sys.frozen
 
 # Build decorator that uses the setup_environment/setup_environment
 with_environment = with_setup(setup_environment, teardown_environment)
 
 @contextmanager
 def patch_get_home_dir(dirpath):
     orig_get_home_dir = path.get_home_dir
     path.get_home_dir = lambda : dirpath
     try:
         yield
     finally:
         path.get_home_dir = orig_get_home_dir
 
 @skip_if_not_win32
 @with_environment
 def test_get_home_dir_1():
     """Testcase for py2exe logic, un-compressed lib
     """
     unfrozen = path.get_home_dir()
     sys.frozen = True
 
     #fake filename for IPython.__init__
     IPython.__file__ = abspath(join(HOME_TEST_DIR, "Lib/IPython/__init__.py"))
 
     home_dir = path.get_home_dir()
     nt.assert_equal(home_dir, unfrozen)
 
 
 @skip_if_not_win32
 @with_environment
 def test_get_home_dir_2():
     """Testcase for py2exe logic, compressed lib
     """
     unfrozen = path.get_home_dir()
     sys.frozen = True
     #fake filename for IPython.__init__
     IPython.__file__ = abspath(join(HOME_TEST_DIR, "Library.zip/IPython/__init__.py")).lower()
 
     home_dir = path.get_home_dir(True)
     nt.assert_equal(home_dir, unfrozen)
 
 
 @with_environment
 def test_get_home_dir_3():
     """get_home_dir() uses $HOME if set"""
     env["HOME"] = HOME_TEST_DIR
     home_dir = path.get_home_dir(True)
     # get_home_dir expands symlinks
     nt.assert_equal(home_dir, os.path.realpath(env["HOME"]))
 
 
 @with_environment
 def test_get_home_dir_4():
     """get_home_dir() still works if $HOME is not set"""
 
     if 'HOME' in env: del env['HOME']
     # this should still succeed, but we don't care what the answer is
     home = path.get_home_dir(False)
 
 @with_environment
 def test_get_home_dir_5():
     """raise HomeDirError if $HOME is specified, but not a writable dir"""
     env['HOME'] = abspath(HOME_TEST_DIR+'garbage')
     # set os.name = posix, to prevent My Documents fallback on Windows
     os.name = 'posix'
     nt.assert_raises(path.HomeDirError, path.get_home_dir, True)
 
 # Should we stub wreg fully so we can run the test on all platforms?
 @skip_if_not_win32
 @with_environment
 def test_get_home_dir_8():
     """Using registry hack for 'My Documents', os=='nt'
 
     HOMESHARE, HOMEDRIVE, HOMEPATH, USERPROFILE and others are missing.
     """
     os.name = 'nt'
     # Remove from stub environment all keys that may be set
     for key in ['HOME', 'HOMESHARE', 'HOMEDRIVE', 'HOMEPATH', 'USERPROFILE']:
         env.pop(key, None)
 
     class key:
         def Close(self):
             pass
 
     with patch.object(wreg, 'OpenKey', return_value=key()), \
          patch.object(wreg, 'QueryValueEx', return_value=[abspath(HOME_TEST_DIR)]):
         home_dir = path.get_home_dir()
     nt.assert_equal(home_dir, abspath(HOME_TEST_DIR))
 
 
 @with_environment
 def test_get_ipython_dir_1():
     """test_get_ipython_dir_1, Testcase to see if we can call get_ipython_dir without Exceptions."""
     env_ipdir = os.path.join("someplace", ".ipython")
     path._writable_dir = lambda path: True
     env['IPYTHONDIR'] = env_ipdir
     ipdir = path.get_ipython_dir()
     nt.assert_equal(ipdir, env_ipdir)
 
 
 @with_environment
 def test_get_ipython_dir_2():
     """test_get_ipython_dir_2, Testcase to see if we can call get_ipython_dir without Exceptions."""
     with patch_get_home_dir('someplace'):
         path.get_xdg_dir = lambda : None
         path._writable_dir = lambda path: True
         os.name = "posix"
         env.pop('IPYTHON_DIR', None)
         env.pop('IPYTHONDIR', None)
         env.pop('XDG_CONFIG_HOME', None)
         ipdir = path.get_ipython_dir()
         nt.assert_equal(ipdir, os.path.join("someplace", ".ipython"))
 
 @with_environment
 def test_get_ipython_dir_3():
     """test_get_ipython_dir_3, move XDG if defined, and .ipython doesn't exist."""
     tmphome = TemporaryDirectory()
     try:
         with patch_get_home_dir(tmphome.name):
             os.name = "posix"
             env.pop('IPYTHON_DIR', None)
             env.pop('IPYTHONDIR', None)
             env['XDG_CONFIG_HOME'] = XDG_TEST_DIR
 
             with warnings.catch_warnings(record=True) as w:
                 ipdir = path.get_ipython_dir()
 
             nt.assert_equal(ipdir, os.path.join(tmphome.name, ".ipython"))
             if sys.platform != 'darwin':
                 nt.assert_equal(len(w), 1)
                 nt.assert_in('Moving', str(w[0]))
     finally:
         tmphome.cleanup()
 
 @with_environment
 def test_get_ipython_dir_4():
     """test_get_ipython_dir_4, warn if XDG and home both exist."""
     with patch_get_home_dir(HOME_TEST_DIR):
         os.name = "posix"
         env.pop('IPYTHON_DIR', None)
         env.pop('IPYTHONDIR', None)
         env['XDG_CONFIG_HOME'] = XDG_TEST_DIR
         try:
             os.mkdir(os.path.join(XDG_TEST_DIR, 'ipython'))
         except OSError as e:
             if e.errno != errno.EEXIST:
                 raise
 
         with warnings.catch_warnings(record=True) as w:
             ipdir = path.get_ipython_dir()
 
         nt.assert_equal(ipdir, os.path.join(HOME_TEST_DIR, ".ipython"))
         if sys.platform != 'darwin':
             nt.assert_equal(len(w), 1)
             nt.assert_in('Ignoring', str(w[0]))
 
 @with_environment
 def test_get_ipython_dir_5():
     """test_get_ipython_dir_5, use .ipython if exists and XDG defined, but doesn't exist."""
     with patch_get_home_dir(HOME_TEST_DIR):
         os.name = "posix"
         env.pop('IPYTHON_DIR', None)
         env.pop('IPYTHONDIR', None)
         env['XDG_CONFIG_HOME'] = XDG_TEST_DIR
         try:
             os.rmdir(os.path.join(XDG_TEST_DIR, 'ipython'))
         except OSError as e:
             if e.errno != errno.ENOENT:
                 raise
         ipdir = path.get_ipython_dir()
         nt.assert_equal(ipdir, IP_TEST_DIR)
 
 @with_environment
 def test_get_ipython_dir_6():
     """test_get_ipython_dir_6, use home over XDG if defined and neither exist."""
     xdg = os.path.join(HOME_TEST_DIR, 'somexdg')
     os.mkdir(xdg)
     shutil.rmtree(os.path.join(HOME_TEST_DIR, '.ipython'))
     with patch_get_home_dir(HOME_TEST_DIR):
         orig_get_xdg_dir = path.get_xdg_dir
         path.get_xdg_dir = lambda : xdg
         try:
             os.name = "posix"
             env.pop('IPYTHON_DIR', None)
             env.pop('IPYTHONDIR', None)
             env.pop('XDG_CONFIG_HOME', None)
             with warnings.catch_warnings(record=True) as w:
                 ipdir = path.get_ipython_dir()
 
             nt.assert_equal(ipdir, os.path.join(HOME_TEST_DIR, '.ipython'))
             nt.assert_equal(len(w), 0)
         finally:
             path.get_xdg_dir = orig_get_xdg_dir
 
 @with_environment
 def test_get_ipython_dir_7():
     """test_get_ipython_dir_7, test home directory expansion on IPYTHONDIR"""
     path._writable_dir = lambda path: True
     home_dir = os.path.normpath(os.path.expanduser('~'))
     env['IPYTHONDIR'] = os.path.join('~', 'somewhere')
     ipdir = path.get_ipython_dir()
     nt.assert_equal(ipdir, os.path.join(home_dir, 'somewhere'))
 
 @skip_win32
 @with_environment
 def test_get_ipython_dir_8():
     """test_get_ipython_dir_8, test / home directory"""
     old = path._writable_dir, path.get_xdg_dir
     try:
         path._writable_dir = lambda path: bool(path)
         path.get_xdg_dir = lambda: None
         env.pop('IPYTHON_DIR', None)
         env.pop('IPYTHONDIR', None)
         env['HOME'] = '/'
         nt.assert_equal(path.get_ipython_dir(), '/.ipython')
     finally:
         path._writable_dir, path.get_xdg_dir = old
 
 @with_environment
 def test_get_xdg_dir_0():
     """test_get_xdg_dir_0, check xdg_dir"""
     reload(path)
     path._writable_dir = lambda path: True
     path.get_home_dir = lambda : 'somewhere'
     os.name = "posix"
     sys.platform = "linux2"
     env.pop('IPYTHON_DIR', None)
     env.pop('IPYTHONDIR', None)
     env.pop('XDG_CONFIG_HOME', None)
 
     nt.assert_equal(path.get_xdg_dir(), os.path.join('somewhere', '.config'))
 
 
 @with_environment
 def test_get_xdg_dir_1():
     """test_get_xdg_dir_1, check nonexistant xdg_dir"""
     reload(path)
     path.get_home_dir = lambda : HOME_TEST_DIR
     os.name = "posix"
     sys.platform = "linux2"
     env.pop('IPYTHON_DIR', None)
     env.pop('IPYTHONDIR', None)
     env.pop('XDG_CONFIG_HOME', None)
     nt.assert_equal(path.get_xdg_dir(), None)
 
 @with_environment
 def test_get_xdg_dir_2():
     """test_get_xdg_dir_2, check xdg_dir default to ~/.config"""
     reload(path)
     path.get_home_dir = lambda : HOME_TEST_DIR
     os.name = "posix"
     sys.platform = "linux2"
     env.pop('IPYTHON_DIR', None)
     env.pop('IPYTHONDIR', None)
     env.pop('XDG_CONFIG_HOME', None)
     cfgdir=os.path.join(path.get_home_dir(), '.config')
     if not os.path.exists(cfgdir):
         os.makedirs(cfgdir)
 
     nt.assert_equal(path.get_xdg_dir(), cfgdir)
 
 @with_environment
 def test_get_xdg_dir_3():
     """test_get_xdg_dir_3, check xdg_dir not used on OS X"""
     reload(path)
     path.get_home_dir = lambda : HOME_TEST_DIR
     os.name = "posix"
     sys.platform = "darwin"
     env.pop('IPYTHON_DIR', None)
     env.pop('IPYTHONDIR', None)
     env.pop('XDG_CONFIG_HOME', None)
     cfgdir=os.path.join(path.get_home_dir(), '.config')
     if not os.path.exists(cfgdir):
         os.makedirs(cfgdir)
 
     nt.assert_equal(path.get_xdg_dir(), None)
 
 def test_filefind():
     """Various tests for filefind"""
     f = tempfile.NamedTemporaryFile()
     # print 'fname:',f.name
     alt_dirs = path.get_ipython_dir()
     t = path.filefind(f.name, alt_dirs)
     # print 'found:',t
 
 @with_environment
 def test_get_ipython_cache_dir():
     os.environ["HOME"] = HOME_TEST_DIR
     if os.name == 'posix' and sys.platform != 'darwin':
         # test default
         os.makedirs(os.path.join(HOME_TEST_DIR, ".cache"))
         os.environ.pop("XDG_CACHE_HOME", None)
         ipdir = path.get_ipython_cache_dir()
         nt.assert_equal(os.path.join(HOME_TEST_DIR, ".cache", "ipython"),
                         ipdir)
         nt.assert_true(os.path.isdir(ipdir))
 
         # test env override
         os.environ["XDG_CACHE_HOME"] = XDG_CACHE_DIR
         ipdir = path.get_ipython_cache_dir()
         nt.assert_true(os.path.isdir(ipdir))
         nt.assert_equal(ipdir, os.path.join(XDG_CACHE_DIR, "ipython"))
     else:
         nt.assert_equal(path.get_ipython_cache_dir(),
                         path.get_ipython_dir())
 
 def test_get_ipython_package_dir():
     ipdir = path.get_ipython_package_dir()
     nt.assert_true(os.path.isdir(ipdir))
 
 
 def test_get_ipython_module_path():
     ipapp_path = path.get_ipython_module_path('IPython.terminal.ipapp')
     nt.assert_true(os.path.isfile(ipapp_path))
 
 
 @dec.skip_if_not_win32
 def test_get_long_path_name_win32():
     with TemporaryDirectory() as tmpdir:
 
         # Make a long path. Expands the path of tmpdir prematurely as it may already have a long 
         # path component, so ensure we include the long form of it
         long_path = os.path.join(path.get_long_path_name(tmpdir), u'this is my long path name')
         os.makedirs(long_path)
 
         # Test to see if the short path evaluates correctly.
         short_path = os.path.join(tmpdir, u'THISIS~1')
         evaluated_path = path.get_long_path_name(short_path)
         nt.assert_equal(evaluated_path.lower(), long_path.lower())
 
 
 @dec.skip_win32
 def test_get_long_path_name():
     p = path.get_long_path_name('/usr/local')
     nt.assert_equal(p,'/usr/local')
 
 @dec.skip_win32 # can't create not-user-writable dir on win
 @with_environment
 def test_not_writable_ipdir():
     tmpdir = tempfile.mkdtemp()
     os.name = "posix"
     env.pop('IPYTHON_DIR', None)
     env.pop('IPYTHONDIR', None)
     env.pop('XDG_CONFIG_HOME', None)
     env['HOME'] = tmpdir
     ipdir = os.path.join(tmpdir, '.ipython')
     os.mkdir(ipdir, 0o555)
     try:
         open(os.path.join(ipdir, "_foo_"), 'w').close()
     except IOError:
         pass
     else:
         # I can still write to an unwritable dir,
         # assume I'm root and skip the test
         raise SkipTest("I can't create directories that I can't write to")
     with AssertPrints('is not a writable location', channel='stderr'):
         ipdir = path.get_ipython_dir()
     env.pop('IPYTHON_DIR', None)
 
 def test_unquote_filename():
     for win32 in (True, False):
         nt.assert_equal(path.unquote_filename('foo.py', win32=win32), 'foo.py')
         nt.assert_equal(path.unquote_filename('foo bar.py', win32=win32), 'foo bar.py')
     nt.assert_equal(path.unquote_filename('"foo.py"', win32=True), 'foo.py')
     nt.assert_equal(path.unquote_filename('"foo bar.py"', win32=True), 'foo bar.py')
     nt.assert_equal(path.unquote_filename("'foo.py'", win32=True), 'foo.py')
     nt.assert_equal(path.unquote_filename("'foo bar.py'", win32=True), 'foo bar.py')
     nt.assert_equal(path.unquote_filename('"foo.py"', win32=False), '"foo.py"')
     nt.assert_equal(path.unquote_filename('"foo bar.py"', win32=False), '"foo bar.py"')
     nt.assert_equal(path.unquote_filename("'foo.py'", win32=False), "'foo.py'")
     nt.assert_equal(path.unquote_filename("'foo bar.py'", win32=False), "'foo bar.py'")
 
 @with_environment
 def test_get_py_filename():
     os.chdir(TMP_TEST_DIR)
     for win32 in (True, False):
         with make_tempfile('foo.py'):
             nt.assert_equal(path.get_py_filename('foo.py', force_win32=win32), 'foo.py')
             nt.assert_equal(path.get_py_filename('foo', force_win32=win32), 'foo.py')
         with make_tempfile('foo'):
             nt.assert_equal(path.get_py_filename('foo', force_win32=win32), 'foo')
             nt.assert_raises(IOError, path.get_py_filename, 'foo.py', force_win32=win32)
         nt.assert_raises(IOError, path.get_py_filename, 'foo', force_win32=win32)
         nt.assert_raises(IOError, path.get_py_filename, 'foo.py', force_win32=win32)
         true_fn = 'foo with spaces.py'
         with make_tempfile(true_fn):
             nt.assert_equal(path.get_py_filename('foo with spaces', force_win32=win32), true_fn)
             nt.assert_equal(path.get_py_filename('foo with spaces.py', force_win32=win32), true_fn)
             if win32:
                 nt.assert_equal(path.get_py_filename('"foo with spaces.py"', force_win32=True), true_fn)
                 nt.assert_equal(path.get_py_filename("'foo with spaces.py'", force_win32=True), true_fn)
             else:
                 nt.assert_raises(IOError, path.get_py_filename, '"foo with spaces.py"', force_win32=False)
                 nt.assert_raises(IOError, path.get_py_filename, "'foo with spaces.py'", force_win32=False)
 
 @onlyif_unicode_paths
 def test_unicode_in_filename():
     """When a file doesn't exist, the exception raised should be safe to call
     str() on - i.e. in Python 2 it must only have ASCII characters.
     
     https://github.com/ipython/ipython/issues/875
     """
     try:
         # these calls should not throw unicode encode exceptions
         path.get_py_filename(u'fooéè.py',  force_win32=False)
     except IOError as ex:
         str(ex)
 
 
 class TestShellGlob(object):
 
     @classmethod
     def setUpClass(cls):
         cls.filenames_start_with_a = ['a0', 'a1', 'a2']
         cls.filenames_end_with_b = ['0b', '1b', '2b']
         cls.filenames = cls.filenames_start_with_a + cls.filenames_end_with_b
         cls.tempdir = TemporaryDirectory()
         td = cls.tempdir.name
 
         with cls.in_tempdir():
             # Create empty files
             for fname in cls.filenames:
                 open(os.path.join(td, fname), 'w').close()
 
     @classmethod
     def tearDownClass(cls):
         cls.tempdir.cleanup()
 
     @classmethod
     @contextmanager
     def in_tempdir(cls):
         save = py3compat.getcwd()
         try:
             os.chdir(cls.tempdir.name)
             yield
         finally:
             os.chdir(save)
 
     def check_match(self, patterns, matches):
         with self.in_tempdir():
             # glob returns unordered list. that's why sorted is required.
             nt.assert_equals(sorted(path.shellglob(patterns)),
                              sorted(matches))
 
     def common_cases(self):
         return [
             (['*'], self.filenames),
             (['a*'], self.filenames_start_with_a),
             (['*c'], ['*c']),
             (['*', 'a*', '*b', '*c'], self.filenames
                                       + self.filenames_start_with_a
                                       + self.filenames_end_with_b
                                       + ['*c']),
             (['a[012]'], self.filenames_start_with_a),
         ]
 
     @skip_win32
     def test_match_posix(self):
         for (patterns, matches) in self.common_cases() + [
                 ([r'\*'], ['*']),
                 ([r'a\*', 'a*'], ['a*'] + self.filenames_start_with_a),
                 ([r'a\[012]'], ['a[012]']),
                 ]:
             yield (self.check_match, patterns, matches)
 
     @skip_if_not_win32
     def test_match_windows(self):
         for (patterns, matches) in self.common_cases() + [
                 # In windows, backslash is interpreted as path
                 # separator.  Therefore, you can't escape glob
                 # using it.
                 ([r'a\*', 'a*'], [r'a\*'] + self.filenames_start_with_a),
                 ([r'a\[012]'], [r'a\[012]']),
                 ]:
             yield (self.check_match, patterns, matches)
 
 
 def test_unescape_glob():
     nt.assert_equals(path.unescape_glob(r'\*\[\!\]\?'), '*[!]?')
     nt.assert_equals(path.unescape_glob(r'\\*'), r'\*')
     nt.assert_equals(path.unescape_glob(r'\\\*'), r'\*')
     nt.assert_equals(path.unescape_glob(r'\\a'), r'\a')
     nt.assert_equals(path.unescape_glob(r'\a'), r'\a')
 
 
 def test_ensure_dir_exists():
     with TemporaryDirectory() as td:
         d = os.path.join(td, u'∂ir')
         path.ensure_dir_exists(d) # create it
         assert os.path.isdir(d)
         path.ensure_dir_exists(d) # no-op
         f = os.path.join(td, u'ƒile')
         open(f, 'w').close() # touch
         with nt.assert_raises(IOError):
             path.ensure_dir_exists(f)
 
 class TestLinkOrCopy(object):
     def setUp(self):
         self.tempdir = TemporaryDirectory()
         self.src = self.dst("src")
         with open(self.src, "w") as f:
             f.write("Hello, world!")
 
     def tearDown(self):
         self.tempdir.cleanup()
 
     def dst(self, *args):
         return os.path.join(self.tempdir.name, *args)
 
     def assert_inode_not_equal(self, a, b):
         nt.assert_not_equals(os.stat(a).st_ino, os.stat(b).st_ino,
                              "%r and %r do reference the same indoes" %(a, b))
 
     def assert_inode_equal(self, a, b):
         nt.assert_equals(os.stat(a).st_ino, os.stat(b).st_ino,
                          "%r and %r do not reference the same indoes" %(a, b))
 
     def assert_content_equal(self, a, b):
         with open(a) as a_f:
             with open(b) as b_f:
                 nt.assert_equals(a_f.read(), b_f.read())
 
     @skip_win32
     def test_link_successful(self):
         dst = self.dst("target")
         path.link_or_copy(self.src, dst)
         self.assert_inode_equal(self.src, dst)
 
     @skip_win32
     def test_link_into_dir(self):
         dst = self.dst("some_dir")
         os.mkdir(dst)
         path.link_or_copy(self.src, dst)
         expected_dst = self.dst("some_dir", os.path.basename(self.src))
         self.assert_inode_equal(self.src, expected_dst)
 
     @skip_win32
     def test_target_exists(self):
         dst = self.dst("target")
         open(dst, "w").close()
         path.link_or_copy(self.src, dst)
         self.assert_inode_equal(self.src, dst)
 
     @skip_win32
     def test_no_link(self):
         real_link = os.link
         try:
             del os.link
             dst = self.dst("target")
             path.link_or_copy(self.src, dst)
             self.assert_content_equal(self.src, dst)
             self.assert_inode_not_equal(self.src, dst)
         finally:
             os.link = real_link
 
     @skip_if_not_win32
     def test_windows(self):
         dst = self.dst("target")
         path.link_or_copy(self.src, dst)
         self.assert_content_equal(self.src, dst)
+
+    def test_link_twice(self):
+        # Linking the same file twice shouldn't leave duplicates around.
+        # See https://github.com/ipython/ipython/issues/6450
+        dst = self.dst('target')
+        path.link_or_copy(self.src, dst)
+        path.link_or_copy(self.src, dst)
+        self.assert_inode_equal(self.src, dst)
+        nt.assert_equal(sorted(os.listdir(self.tempdir.name)), ['src', 'target'])