Added some support for extended filesystem attributes

CHANGES.md

@@ -4,6 +4,8 @@ The release versions are PyPi releases.
 ## Version 3.5 (as yet unreleased)
 
 #### New Features
+  * added some support for extended filesystem attributes under Linux 
+  ([#423](../../issues/423)) 
   * added support for null device ([#418](../../issues/418))
 
 #### Infrastructure

pyfakefs/fake_filesystem.py

@@ -241,6 +241,8 @@ def __init__(self, name, st_mode=S_IFREG | PERM_DEF_FILE,
             len(self._byte_contents) if self._byte_contents is not None else 0)
         self.epoch = 0
         self.parent_dir = None
+        # Linux/Python 3 specific: extended file system attributes
+        self.xattr = {}
 
     @property
     def byte_contents(self):
@@ -840,6 +842,10 @@ def __init__(self, path_separator=os.path.sep, total_size=None):
         self._add_standard_streams()
         self.dev_null = FakeNullFile(self)
 
+    @property
+    def is_linux(self):
+        return not self.is_windows_fs and not self.is_macos
+
     def reset(self, total_size=None):
         """Remove all file system contents and reset the root."""
         self.root = FakeDirectory(self.path_separator, filesystem=self)
@@ -3687,11 +3693,121 @@ def listdir(self, target_directory):
         """
         return self.filesystem.listdir(target_directory)
 
-    if sys.platform.startswith('linux') and sys.version_info >= (3, 3):
+    if sys.version_info >= (3, 3):
+        XATTR_CREATE = 1
+        XATTR_REPLACE = 2
+
+        def getxattr(self, path, attribute, follow_symlinks=True):
+            """Return the value of the given extended filesystem attribute for
+            `path`.
+
+            Args:
+                path: File path, file descriptor or path-like object (for
+                    Python >= 3.6).
+                attribute: (str or bytes) The attribute name.
+                follow_symlinks: (bool) If True (the default), symlinks in the
+                    path are traversed.
+
+            Returns:
+                The contents of the extended attribute as bytes or None if
+                the attribute does not exist.
+
+            Raises:
+                OSError: if the path does not exist.
+            """
+            if not self.filesystem.is_linux:
+                raise AttributeError(
+                    "module 'os' has no attribute 'getxattr'")
+
+            if isinstance(attribute, bytes):
+                attribute = attribute.decode(sys.getfilesystemencoding())
+            file_obj = self.filesystem.resolve(path, follow_symlinks,
+                                               allow_fd=True)
+            return file_obj.xattr.get(attribute)
+
         def listxattr(self, path=None, follow_symlinks=True):
-            """Dummy implementation that returns an empty list -
-            used by shutil."""
-            return []
+            """Return a list of the extended filesystem attributes on `path`.
+
+            Args:
+                path: File path, file descriptor or path-like object (for
+                    Python >= 3.6). If None, the current directory is used.
+                follow_symlinks: (bool) If True (the default), symlinks in the
+                    path are traversed.
+
+            Returns:
+                A list of all attribute names for the given path as str.
+
+            Raises:
+                OSError: if the path does not exist.
+            """
+            if not self.filesystem.is_linux:
+                raise AttributeError(
+                    "module 'os' has no attribute 'listxattr'")
+
+            if path is None:
+                path = self.getcwd()
+            file_obj = self.filesystem.resolve(path, follow_symlinks,
+                                               allow_fd=True)
+            return list(file_obj.xattr.keys())
+
+        def removexattr(self, path, attribute, follow_symlinks=True):
+            """Removes the extended filesystem attribute attribute from `path`.
+
+            Args:
+                path: File path, file descriptor or path-like object (for
+                    Python >= 3.6).
+                attribute: (str or bytes) The attribute name.
+                follow_symlinks: (bool) If True (the default), symlinks in the
+                    path are traversed.
+
+            Raises:
+                OSError: if the path does not exist.
+            """
+            if not self.filesystem.is_linux:
+                raise AttributeError(
+                    "module 'os' has no attribute 'removexattr'")
+
+            if isinstance(attribute, bytes):
+                attribute = attribute.decode(sys.getfilesystemencoding())
+            file_obj = self.filesystem.resolve(path, follow_symlinks,
+                                               allow_fd=True)
+            if attribute in file_obj.xattr:
+                del file_obj.xattr[attribute]
+
+        def setxattr(self, path, attribute, value,
+                     flags=0, follow_symlinks=True):
+            """Sets the value of the given extended filesystem attribute for
+            `path`.
+
+            Args:
+                path: File path, file descriptor or path-like object (for
+                    Python >= 3.6).
+                attribute: The attribute name (str or bytes).
+                value: (byte-like) The value to be set.
+                follow_symlinks: (bool) If True (the default), symlinks in the
+                    path are traversed.
+
+            Raises:
+                OSError: if the path does not exist.
+                TypeError: if `value` is not a byte-like object.
+            """
+            if not self.filesystem.is_linux:
+                raise AttributeError(
+                    "module 'os' has no attribute 'setxattr'")
+
+            if isinstance(attribute, bytes):
+                attribute = attribute.decode(sys.getfilesystemencoding())
+            if not is_byte_string(value):
+                raise TypeError('a bytes-like object is required')
+            file_obj = self.filesystem.resolve(path, follow_symlinks,
+                                               allow_fd=True)
+            exists = attribute in file_obj.xattr
+            if exists and flags == self.XATTR_CREATE:
+                self.filesystem.raise_os_error(errno.ENODATA, file_obj.path)
+            if not exists and flags == self.XATTR_REPLACE:
+                self.filesystem.raise_os_error(errno.EEXIST, file_obj.path)
+            file_obj.xattr[attribute] = value
+
 
     if sys.version_info >= (3, 5):
         def scandir(self, path=''):

pyfakefs/tests/fake_os_test.py

@@ -4693,7 +4693,7 @@ def test_path_links_not_resolved(self):
         link_path = self.make_path('A', 'C')
         self.os.symlink(dir_path, link_path)
         self.assertEqual([self.os.path.join(link_path, 'D')],
-                         [f.path for f in self.os.scandir(link_path)])
+                         [f.path for f in self.scandir(link_path)])
 
     def test_inode(self):
         if has_scandir and self.is_windows and self.use_real_fs():
@@ -4771,3 +4771,46 @@ def tearDown(self):
 class RealScandirFdTest(FakeScandirFdTest):
     def use_real_fs(self):
         return True
+
+
+@unittest.skipIf(TestCase.is_python2,
+                 reason='Xattr only supported in Linux/Python 3')
+class FakeExtendedAttributeTest(FakeOsModuleTestBase):
+    def setUp(self):
+        super(FakeExtendedAttributeTest, self).setUp()
+        self.check_linux_only()
+        self.dir_path = self.make_path('foo')
+        self.file_path = self.os.path.join(self.dir_path, 'bar')
+        self.create_file(self.file_path)
+
+    def test_empty_xattr(self):
+        self.assertEqual([], self.os.listxattr(self.dir_path))
+        self.assertEqual([], self.os.listxattr(self.file_path))
+
+    def test_setxattr(self):
+        self.assertRaises(TypeError, self.os.setxattr,
+                                    self.file_path, 'test', 'value')
+        self.assert_raises_os_error(errno.EEXIST, self.os.setxattr,
+                                    self.file_path, 'test', b'value',
+                                    self.os.XATTR_REPLACE)
+        self.os.setxattr(self.file_path, 'test', b'value')
+        self.assertEqual(b'value', self.os.getxattr(self.file_path, 'test'))
+        self.assert_raises_os_error(errno.ENODATA, self.os.setxattr,
+                                    self.file_path, 'test', b'value',
+                                    self.os.XATTR_CREATE)
+
+    def test_removeattr(self):
+        self.os.removexattr(self.file_path, 'test')
+        self.assertEqual([], self.os.listxattr(self.file_path))
+        self.os.setxattr(self.file_path, b'test', b'value')
+        self.assertEqual(['test'], self.os.listxattr(self.file_path))
+        self.assertEqual(b'value', self.os.getxattr(self.file_path, 'test'))
+        self.os.removexattr(self.file_path, 'test')
+        self.assertEqual([], self.os.listxattr(self.file_path))
+        self.assertIsNone(self.os.getxattr(self.file_path, 'test'))
+
+    def test_default_path(self):
+        self.os.chdir(self.dir_path)
+        self.os.setxattr(self.dir_path, b'test', b'value')
+        self.assertEqual(['test'], self.os.listxattr())
+        self.assertEqual(b'value', self.os.getxattr(self.dir_path, 'test'))