Returns an error code if no command is present

tools/isolate/isolate.py

 #!/usr/bin/env python
 # 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.
 
 """Does one of the following depending on the --mode argument:
   check     Verifies all the inputs exist, touches the file specified with
             --result and exits.
   hashtable Puts a manifest file and hard links each of the inputs into the
             output directory.
@@ skipping 354 matching lines @@
   """Always uses a temporary directory."""
   try:
     outdir = tempfile.mkdtemp(prefix='isolate')
     recreate_tree(
         outdir, indir, dictfiles.keys(), run_test_from_archive.HARDLINK)
     cwd = os.path.join(outdir, relative_cwd)
     if not os.path.isdir(cwd):
       os.makedirs(cwd)
     if read_only:
       run_test_from_archive.make_writable(outdir, True)
+    if not cmd:
+      print 'No command to run'
+      return 1
     cmd = trace_inputs.fix_python_path(cmd)
     logging.info('Running %s, cwd=%s' % (cmd, cwd))
     return subprocess.call(cmd, cwd=cwd)
   finally:
     run_test_from_archive.rmtree(outdir)
 
 
 def MODEtrace(
     _outdir, indir, _dictfiles, _read_only, cmd, relative_cwd, resultfile):
   """Shortcut to use trace_inputs.py properly.
 
   It constructs the equivalent of dictfiles. It is hardcoded to base the
   checkout at src/.
   """
   logging.info('Running %s, cwd=%s' % (cmd, os.path.join(indir, relative_cwd)))
   if resultfile:
     # Guesswork here.
     product_dir = os.path.dirname(resultfile)
     if product_dir and indir:
       product_dir = os.path.relpath(product_dir, indir)
   else:
     product_dir = None
+  if not cmd:
+    print 'No command to run'
+    return 1
   return trace_inputs.trace_inputs(
       '%s.log' % resultfile,
       cmd,
       indir,
       relative_cwd,
       product_dir,
       False)
 
 
 def get_valid_modes():
   """Returns the modes that can be used."""
   return sorted(
       i[4:] for i in dir(sys.modules[__name__]) if i.startswith('MODE'))
 
 
 def main():
   default_variables = ['OS=%s' % trace_inputs.get_flavor()]
   if sys.platform in ('win32', 'cygwin'):
     default_variables.append('EXECUTABLE_SUFFIX=.exe')
   else:
     default_variables.append('EXECUTABLE_SUFFIX=')
   valid_modes = get_valid_modes()
   parser = optparse.OptionParser(
       usage='%prog [options] [.isolate file]',
       description=sys.modules[__name__].__doc__)
   parser.format_description = lambda *_: parser.description
   parser.add_option(
       '-v', '--verbose',
       action='count',
-      default=2 if 'ISOLATE_DEBUG' in os.environ else 0,
+      default=int(os.environ.get('ISOLATE_DEBUG', 0)),
       help='Use multiple times')
   parser.add_option(
       '-m', '--mode',
       choices=valid_modes,
       help='Determines the action to be taken: %s' % ', '.join(valid_modes))
   parser.add_option(
       '-r', '--result',
       metavar='FILE',
       help='Result file to store the json manifest')
   parser.add_option(
@@ skipping 80 matching lines @@
         command,
         relative_dir,
         options.result)
   except run_test_from_archive.MappingError, e:
     print >> sys.stderr, str(e)
     return 1
 
 
 if __name__ == '__main__':
   sys.exit(main())