Check the existence and executability of scm commands

gclient_scm.py

Index: gclient_scm.py
===================================================================
--- gclient_scm.py	(revision 131736)
+++ gclient_scm.py	(working copy)
@@ -76,6 +76,21 @@
   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,
@@ -85,6 +100,7 @@
   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)