Check the existence and executability of scm commands

gclient_scm.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.
 
 """Gclient-specific SCM-specific operations."""
 
 import logging
 import os
 import posixpath
 import re
@@ skipping 58 matching lines @@
     if (url.startswith('git://') or url.startswith('ssh://') or
         url.startswith('git+http://') or url.startswith('git+https://') or
         url.endswith('.git')):
       return 'git'
     elif (url.startswith('http://') or url.startswith('https://') or
           url.startswith('svn://') or url.startswith('svn+ssh://')):
       return 'svn'
   return None
 
 
+def CheckCommandExecutable(cmd):
+  """Find the specified |cmd| in $PATH and checks if it's executable.
+  Raise an exception if fails.  Otherwise do nothing."""
+  paths = os.getenv('PATH').split(':')

[satorux1, 2012/04/11 17:09:14]

this fails if PATH is not set. os.getenv('PATH', '') will make it safe.


Besides, what if this function is called on Windows? I thought the PATH
separator was different on Windows.

[Jun Mukai, 2012/04/12 09:51:14]

Done.

Also introduced os.pathsep instead of ':', which will work  with Windows. 
Thanks for pointing.

+  for path in paths:
+    full_path = os.path.join(path, cmd)
+    if os.path.exists(full_path):
+      if not os.path.isfile(full_path):
+        raise gclient_utils.Error('%s is not a file.' % full_path)
+      if not os.access(full_path, os.X_OK):
+        raise gclient_utils.Error('%s is not executable.' % full_path)
+      return
+  raise gclient_utils.Error('%s command is not found.' % cmd)
+
+
 def CreateSCM(url, root_dir=None, relpath=None):
   SCM_MAP = {
     'svn' : SVNWrapper,
     'git' : GitWrapper,
   }
 
   scm_name = GetScmName(url)
   if not scm_name in SCM_MAP:
     raise gclient_utils.Error('No SCM found for url %s' % url)
+  CheckCommandExecutable(scm_name)
   return SCM_MAP[scm_name](url, root_dir, relpath)
 
 
 # SCMWrapper base class
 
 class SCMWrapper(object):
   """Add necessary glue between all the supported SCM.
 
   This is the abstraction layer to bind to different SCM.
   """
@@ skipping 1031 matching lines @@
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'theirs-conflict'))
     elif options.manually_grab_svn_rev:
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'postpone'))
     elif command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
       new_command.extend(('--accept', 'postpone'))
     return new_command