Reland "Implement FileSystem.rmtree for long paths on Windows"

This is a reland of 2eb368c0

Changed to not allow long paths for the root of the tree
being rmtree'd, so it works on Windows 7.

Original change's description:
> Implement FileSystem.rmtree for long paths on Windows
>
> Changes blinkpy filesystem tests to use remove_contents instead of
> rmtree. remove_contents calls into rmtree, but
>   (1) retries several times to delete the files, and
>   (2) throws by default instead of silently swallowing errors.
> This improves all of the tests. Additionally, the retrying was
> actually necessary to pass many tests (files were otherwise still
> locked during teardown).
>
> Extends the test_long_paths test to check spaces and apostrophes.
>
> FileSystem.rmtree is now implemented on Windows by just calling
> a shell with "rmdir /s /q". This is necessary, because
> shutil.rmtree doesn't work for \\?\C:\ style "extended-length" paths
> on Windows, and several other implementations I tried didn't work:
>   - Loop using os.walk. os.walk doesn't support long paths, and
>     though it seemed to work on the bots, it failed tests locally.
>   - Recursive using os.listdir. os.listdir also doesn't support long
>     paths.
>
> Tested on dawn-win10-* try job on crrev.com/c/2050036/17.
> Found in dawn-win10-* try jobs on crrev.com/c/2050036/4.
>
> Change-Id: I7c67bb12305a41244829e35293edfc88901b76f4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2058065
> Commit-Queue: Kai Ninomiya <kainino@chromium.org>
> Reviewed-by: Robert Ma <robertma@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#742961}

Bug: 1054331
Change-Id: Ib1f7a7ac0109fb77e1d26f1bdb292ad2c95cea24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2092946
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748886}

third_party/blink/tools/blinkpy/common/system/filesystem.py

@@ -41,6 +41,7 @@ import logging
 import os
 import shutil
 import stat
+import subprocess
 import sys
 import tempfile
 import time
@@ -74,6 +75,7 @@ class FileSystem(object):
         (https://msdn.microsoft.com/en-us/library/aa365247.aspx#maxpath)
         """
         if sys.platform == 'win32' and len(path) >= self.WINDOWS_MAX_PATH:
+            assert not path.startswith(r'\\'), "must not already be UNC"
             return ur'\\?\%s' % (self.abspath(path),)
         return path
 
@@ -327,8 +329,34 @@ class FileSystem(object):
 
     def rmtree(self, path, ignore_errors=True, onerror=None):
         """Deletes the directory rooted at path, whether empty or not."""
-        # shutil.rmtree() uses os.path.join() which doesn't support UNC paths.
-        shutil.rmtree(path, ignore_errors=ignore_errors, onerror=onerror)
+        if sys.platform == 'win32':
+            assert not path.startswith(r'\\'), 'root path cannot be UNC-style'
+            path_abs = self.abspath(path)
+
+            # Ensure the root of the tree being rmtree'd is not a long path.
+            # We can't convert it to a long path (using _path_for_access),
+            # because long paths are not supported in 'rmdir' on Windows 7.
+            assert len(path_abs) < self.WINDOWS_MAX_PATH, 'root path is too long'
+
+            # Ensure (hopefully) that the quoting done on the next line is safe.
+            assert '"' not in path_abs, 'path contains a quotation mark (")'
+
+            # Create a shell command to call rmdir. (Note rmdir is a shell
+            # built-in, so it cannot be called as an executable.)
+            cmd = 'rmdir /s /q "{}"'.format(path_abs)
+            try:
+                subprocess.check_call(cmd, shell=True)
+            except subprocess.CalledProcessError as e:
+                if not ignore_errors:
+                    if onerror:
+                        # Unfortunately we can't know the exact file that failed,
+                        # so we conjure up error info from the top level.
+                        onerror('FileSystem.rmtree', path, sys.exc_info())
+                    else:
+                        raise e
+        else:
+            # shutil.rmtree() uses os.path.join() which doesn't support UNC paths.
+            shutil.rmtree(path, ignore_errors=ignore_errors, onerror=onerror)
 
     def remove_contents(self, dirname):
         """Attempts to remove the contents of a directory tree.

third_party/blink/tools/blinkpy/common/system/filesystem_unittest.py

@@ -56,9 +56,10 @@ class GenericFileSystemTests(object):
         fs.chdir(self.orig_cwd)
 
     def teardown_generic_test_dir(self):
-        self.fs.rmtree(self.generic_test_dir)
+        success = self.fs.remove_contents(self.generic_test_dir)
         self.fs.chdir(self.orig_cwd)
         self.generic_test_dir = None
+        self.assertTrue(success)
 
     def test_glob__trailing_asterisk(self):
         self.fs.chdir(self.generic_test_dir)
@@ -112,10 +113,10 @@ class GenericFileSystemTests(object):
 
     def test_rmtree(self):
         self.fs.chdir(self.generic_test_dir)
-        self.fs.rmtree('foo')
+        self.fs.rmtree('doesntexist')
         self.assertTrue(self.fs.exists('foodir'))
         self.assertTrue(self.fs.exists(self.fs.join('foodir', 'baz')))
-        self.fs.rmtree('foodir')
+        self.fs.rmtree('foodir', ignore_errors=False)
         self.assertFalse(self.fs.exists('foodir'))
         self.assertFalse(self.fs.exists(self.fs.join('foodir', 'baz')))
 
@@ -361,3 +362,18 @@ class RealFileSystemTest(unittest.TestCase, GenericFileSystemTests):
         content = self.fs.read_text_file(file2)
         self.fs.remove(file2)  # No exception should be raised.
         self.assertEqual(content, 'hello')
+        # (long_path is left in the filesystem and its removal is tested during cleanup.)
+
+        # On Windows, rmtree can handle trees containing long paths as long as
+        # the root is not a long path.
+        long_path1 = self.fs.join(self.generic_test_dir, 'a' * 100, 'b' * 100 + " 'b")
+        long_path2 = self.fs.join(long_path1, 'c' * 100)
+        self.fs.maybe_make_directory(long_path2)
+        file1 = self.fs.join(long_path2, 'foo')
+        self.fs.write_text_file(file1, 'hello')
+        if sys.platform == 'win32':
+            with self.assertRaises(AssertionError):
+                self.fs.rmtree(long_path2, ignore_errors=False)
+        else:
+            self.fs.rmtree(long_path2, ignore_errors=False)
+        self.fs.rmtree(long_path1, ignore_errors=False)