[NaCl SDK] Refactor sdk_update*.

native_client_sdk/src/build_tools/sdk_tools/sdk_update_common.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Utility functions for sdk_update.py and sdk_update_main.py."""
 
 import errno
 import os
 import shutil
 import subprocess
 import sys
 import time
 
 
 class Error(Exception):
   """Generic error/exception for sdk_update module"""
   pass
 
 
+def MakeDirs(directory):
+  try:
+    os.makedirs(directory)
+  except OSError as e:
+    if e.errno != errno.EEXIST:
+      raise Error('Unable to make directory "%s".\n  %s' % (directory, e))
+

[Sam Clegg, 2012/10/22 22:55:30]

I'm still not completely sold on this pattern.

I prefer an early return if os.path.exists() but that is
really a style thing I guess.

The argument I suppose is that there could be another processes racing with up. 
 However, if some other process
was to create the folder between the two calls I'd argue that its better for
this program to just crash here.  i.e. externally messing with the tree while
this program is not worth defending against.

[binji, 2012/10/23 00:14:09]

Fair enough, we use os.path.exists elsewhere -- may as well be consistent.

+
 def RemoveDir(outdir):
   """Removes the given directory
 
   On Unix systems, this just runs shutil.rmtree, but on Windows, this doesn't
   work when the directory contains junctions (as does our SDK installer).
   Therefore, on Windows, it runs rmdir /S /Q as a shell command.  This always
   does the right thing on Windows. If the directory already didn't exist,
   RemoveDir will return successfully without taking any action.
 
   Args:
     outdir: The directory to delete
 
   Raises:
-    CalledProcessError - if the delete operation fails on Windows
-    OSError - if the delete operation fails on Linux
+    Error - If this operation fails for any reason.
   """
 
   try:
-    shutil.rmtree(outdir)
-  except OSError:
-    if not os.path.exists(outdir):
-      return
-    # On Windows this could be an issue with junctions, so try again with rmdir
-    if sys.platform == 'win32':
-      subprocess.check_call(['rmdir', '/S', '/Q', outdir], shell=True)
+    try:
+      shutil.rmtree(outdir)
+    except OSError:
+      if not os.path.exists(outdir):
+        return
+      # On Windows this could be an issue with junctions, so try again with
+      # rmdir
+      if sys.platform == 'win32':
+        subprocess.check_call(['rmdir', '/S', '/Q', outdir], shell=True)
+  except Exception as e:
+    raise Error('Unable to remove directory "%s"\n  %s' % (outdir, e))
 
 
 def RenameDir(srcdir, destdir):
   """Renames srcdir to destdir. Removes destdir before doing the
      rename if it already exists."""
 
   max_tries = 5
   num_tries = 0
   for num_tries in xrange(max_tries):
     try:
       RemoveDir(destdir)
       shutil.move(srcdir, destdir)
       return
     except OSError as err:
       if err.errno != errno.EACCES:
         raise err
       # If we are here, we didn't exit due to raised exception, so we are
       # handling a Windows flaky access error.  Sleep one second and try
       # again.
       time.sleep(num_tries + 1)
 
   # end of while loop -- could not RenameDir
   raise Error('Could not RenameDir %s => %s after %d tries.\n'
               'Please check that no shells or applications '
               'are accessing files in %s.'
               % (srcdir, destdir, num_tries, destdir))