Check the existence and executability of scm commands

gclient_scm.py

Index: gclient_scm.py
===================================================================
--- gclient_scm.py	(revision 131926)
+++ gclient_scm.py	(working copy)
@@ -76,6 +76,21 @@
   return None
 
 
+def CheckCommandExecutable(cmd):

[M-A Ruel, 2012/04/12 17:37:38]

This belongs to gclient_utils.

[Jun Mukai, 2012/04/13 06:00:53]

Done.

+  """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(os.pathsep)

[M-A Ruel, 2012/04/12 17:37:38]

os.environ['PATH'].split(os.pathsep)

You can safely assume PATH is present.

[Jun Mukai, 2012/04/13 06:00:53]

Done.

+  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)

[M-A Ruel, 2012/04/12 17:37:38]

Why raise? FWIU, 'which' would move on. You should try to compare.

[Jun Mukai, 2012/04/13 06:00:53]

Done.

+      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)

[M-A Ruel, 2012/04/12 17:37:38]

I prefer this function to return the path of the command found or None if not
found, then the caller can throw accordingly.

[Jun Mukai, 2012/04/13 06:00:53]

Done.
The reason for raise was that there could be a few types of errors (not-found /
not-executable), but that's not necessary as you pointed.

+
+
 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)