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Bug 845050 - FileCopier support for symlinks; r=glandium
This commit is contained in:
Gregory Szorc
parent
42e77dc922
commit
fa360ff4ff
@ -2,9 +2,12 @@
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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import errno
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import os
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import re
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import shutil
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import stat
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import uuid
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from mozpack.executables import (
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is_executable,
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may_strip,
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@ -159,6 +162,100 @@ class ExecutableFile(File):
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return True
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class AbsoluteSymlinkFile(File):
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'''File class that is copied by symlinking (if available).
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This class only works if the target path is absolute.
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'''
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def __init__(self, path):
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if not os.path.isabs(path):
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raise ValueError('Symlink target not absolute: %s' % path)
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File.__init__(self, path)
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def copy(self, dest, skip_if_older=True):
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assert isinstance(dest, basestring)
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# The logic in this function is complicated by the fact that symlinks
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# aren't universally supported. So, where symlinks aren't supported, we
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# fall back to file copying. Keep in mind that symlink support is
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# per-filesystem, not per-OS.
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# Handle the simple case where symlinks are definitely not supported by
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# falling back to file copy.
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if not hasattr(os, 'symlink'):
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return File.copy(self, dest, skip_if_older=skip_if_older)
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# Always verify the symlink target path exists.
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if not os.path.exists(self.path):
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raise ErrorMessage('Symlink target path does not exist: %s' % self.path)
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st = None
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try:
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st = os.lstat(dest)
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except OSError as ose:
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if ose.errno != errno.ENOENT:
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raise
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# If the dest is a symlink pointing to us, we have nothing to do.
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# If it's the wrong symlink, the filesystem must support symlinks,
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# so we replace with a proper symlink.
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if st and stat.S_ISLNK(st.st_mode):
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link = os.readlink(dest)
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if link == self.path:
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return False
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os.remove(dest)
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os.symlink(self.path, dest)
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return True
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# If the destination doesn't exist, we try to create a symlink. If that
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# fails, we fall back to copy code.
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if not st:
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try:
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os.symlink(self.path, dest)
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return True
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except OSError:
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return File.copy(self, dest, skip_if_older=skip_if_older)
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# Now the complicated part. If the destination exists, we could be
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# replacing a file with a symlink. Or, the filesystem may not support
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# symlinks. We want to minimize I/O overhead for performance reasons,
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# so we keep the existing destination file around as long as possible.
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# A lot of the system calls would be eliminated if we cached whether
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# symlinks are supported. However, even if we performed a single
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# up-front test of whether the root of the destination directory
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# supports symlinks, there's no guarantee that all operations for that
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# dest (or source) would be on the same filesystem and would support
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# symlinks.
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#
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# Our strategy is to attempt to create a new symlink with a random
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# name. If that fails, we fall back to copy mode. If that works, we
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# remove the old destination and move the newly-created symlink into
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# its place.
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temp_dest = os.path.join(os.path.dirname(dest), str(uuid.uuid4()))
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try:
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os.symlink(self.path, temp_dest)
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# TODO Figure out exactly how symlink creation fails and only trap
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# that.
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except EnvironmentError:
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return File.copy(self, dest, skip_if_older=skip_if_older)
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# If removing the original file fails, don't forget to clean up the
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# temporary symlink.
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try:
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os.remove(dest)
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except EnvironmentError:
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os.remove(temp_dest)
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raise
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os.rename(temp_dest, dest)
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return True
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class GeneratedFile(BaseFile):
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'''
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File class for content with no previous existence on the filesystem.
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@ -3,6 +3,7 @@
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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from mozpack.files import (
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AbsoluteSymlinkFile,
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Dest,
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File,
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GeneratedFile,
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@ -216,6 +217,112 @@ class TestFile(TestWithTmpDir):
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self.assertEqual('fooo', open(dest, 'rb').read())
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class TestAbsoluteSymlinkFile(TestWithTmpDir):
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def setUp(self):
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TestWithTmpDir.setUp(self)
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self.symlink_supported = False
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if not hasattr(os, 'symlink'):
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return
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dummy_path = self.tmppath('dummy_file')
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with open(dummy_path, 'a'):
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pass
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try:
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os.symlink(dummy_path, self.tmppath('dummy_symlink'))
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os.remove(self.tmppath('dummy_symlink'))
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except EnvironmentError:
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pass
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finally:
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os.remove(dummy_path)
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def test_absolute_relative(self):
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AbsoluteSymlinkFile('/foo')
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with self.assertRaisesRegexp(ValueError, 'Symlink target not absolute'):
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AbsoluteSymlinkFile('./foo')
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def test_symlink_file(self):
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source = self.tmppath('test_path')
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with open(source, 'wt') as fh:
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fh.write('Hello world')
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s = AbsoluteSymlinkFile(source)
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dest = self.tmppath('symlink')
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self.assertTrue(s.copy(dest))
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if self.symlink_supported:
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self.assertTrue(os.path.islink(dest))
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link = os.readlink(dest)
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self.assertEqual(link, source)
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else:
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self.assertTrue(os.path.isfile(dest))
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content = open(dest).read()
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self.assertEqual(content, 'Hello world')
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def test_replace_file_with_symlink(self):
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# If symlinks are supported, an existing file should be replaced by a
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# symlink.
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source = self.tmppath('test_path')
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with open(source, 'wt') as fh:
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fh.write('source')
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dest = self.tmppath('dest')
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with open(dest, 'a'):
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pass
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s = AbsoluteSymlinkFile(source)
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s.copy(dest, skip_if_older=False)
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if self.symlink_supported:
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self.assertTrue(os.path.islink(dest))
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link = os.readlink(dest)
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self.assertEqual(link, source)
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else:
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self.assertTrue(os.path.isfile(dest))
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content = open(dest).read()
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self.assertEqual(content, 'source')
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def test_replace_symlink(self):
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if not self.symlink_supported:
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return
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source= self.tmppath('source')
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dest = self.tmppath('dest')
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os.symlink(self.tmppath('bad'), dest)
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self.assertTrue(os.path.islink(dest))
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s = AbsoluteSymlinkFile(source)
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self.assertTrue(s.copy(dest))
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self.assertTrue(os.path.islink(dest))
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link = os.readlink(dest)
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self.assertEqual(link, source)
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def test_noop(self):
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if not hasattr(os, 'symlink'):
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return
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source = self.tmppath('source')
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dest = self.tmppath('dest')
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with open(source, 'a'):
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pass
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os.symlink(source, dest)
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link = os.readlink(dest)
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self.assertEqual(link, source)
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s = AbsoluteSymlinkFile(source)
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self.assertFalse(s.copy(dest))
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link = os.readlink(dest)
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self.assertEqual(link, source)
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class TestGeneratedFile(TestWithTmpDir):
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def test_generated_file(self):
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'''
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