Check binary existence in gclient: 2nd try.

gclient_scm.py

Index: gclient_scm.py
===================================================================
--- gclient_scm.py	(revision 132543)
+++ gclient_scm.py	(working copy)
@@ -85,7 +85,10 @@
   scm_name = GetScmName(url)
   if not scm_name in SCM_MAP:
     raise gclient_utils.Error('No SCM found for url %s' % url)
-  return SCM_MAP[scm_name](url, root_dir, relpath)
+  found_scm = SCM_MAP[scm_name](url, root_dir, relpath)
+  if not found_scm.BinaryExists():
+    raise gclient_utils.Error('%s command not found' % scm_name)
+  return found_scm
 
 
 # SCMWrapper base class
@@ -105,7 +108,19 @@
       self.relpath = self.relpath.replace('/', os.sep)
     if self.relpath and self._root_dir:
       self.checkout_path = os.path.join(self._root_dir, self.relpath)
+    self._checker_command = 'help'
+    self._binary_name = None
 
+  def BinaryExists(self):

[M-A Ruel, 2012/04/17 12:15:55]

This function may be called over 100 times for a gclient checkout. On windows,
this can be a significant slow down. As such, I recommend making it a
@classmethod, have a class level variable to know if it was detected, default it
to None, and if cls._binary_exist is None:
  try:
    cls._binary_exist = gclient_utils.CheckCall(...)
  except OSError:
    cls._binary_exist = False
return cls._binary_exist

Note that scm.py already has a function to get the tool's version,
SVN.AssertVersion() and GIT.AssertVersion. It'd probably be better to call this
function, since it's called eventually and it's already caching its return
value.

[Jun Mukai, 2012/04/18 02:46:36]

Oh, got it.  Modified to use AssertVersion.

+    """Returns true if the command exists."""
+    # Do not call _Run() because this we don't want to leave any messages for
+    # this check.
+    try:
+      return gclient_utils.CheckCallAndFilter(
+          [self._binary_name, self._checker_command], print_stdout=False) == 0
+    except OSError:
+      return False
+
   def RunCommand(self, command, options, args, file_list=None):
     # file_list will have all files that are modified appended to it.
     if file_list is None:
@@ -132,6 +147,7 @@
     if url.startswith('git+http://') or url.startswith('git+https://'):
       url = url[4:]
     SCMWrapper.__init__(self, url, root_dir, relpath)
+    self._binary_name = 'git'
 
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
@@ -759,7 +775,7 @@
 
   def _Capture(self, args):
     return subprocess2.check_output(
-        ['git'] + args,
+        [self._binary_name] + args,
         stderr=subprocess2.PIPE,
         cwd=self.checkout_path).strip()
 
@@ -769,12 +785,16 @@
     stdout = kwargs.get('stdout', sys.stdout)
     stdout.write('\n________ running \'git %s\' in \'%s\'\n' % (
                  ' '.join(args), kwargs['cwd']))
-    gclient_utils.CheckCallAndFilter(['git'] + args, **kwargs)
+    gclient_utils.CheckCallAndFilter([self._binary_name] + args, **kwargs)
 
 
 class SVNWrapper(SCMWrapper):
   """ Wrapper for SVN """
 
+  def __init__(self, url=None, root_dir=None, relpath=None):
+    SCMWrapper.__init__(self, url, root_dir, relpath)
+    self._binary_name = 'svn'
+
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
     time zone)."""
@@ -1094,7 +1114,7 @@
   def _Run(self, args, options, **kwargs):
     """Runs a commands that goes to stdout."""
     kwargs.setdefault('cwd', self.checkout_path)
-    gclient_utils.CheckCallAndFilterAndHeader(['svn'] + args,
+    gclient_utils.CheckCallAndFilterAndHeader([self._binary_name] + args,
         always=options.verbose, **kwargs)
 
   def _RunAndGetFileList(self, args, options, file_list, cwd=None):