chromite: Switch from execve to import.

bin/chromite

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Wrapper for the chromite shell.
 
 This script is intended to run in several ways:
 - Outside the chroot, it should be _copied_ to someplace that is in the
   path (like depot_tools).  It will search for the right chromite by looking
   for a file 'chromite/shell/main.py' upward based on the CWD.
 - Inside the chroot, it might be _either_ copied to someplace in the path (since
   depot_tools is in the path in the chroot) or it might run from chromite/bin
   directly, which should be in the PATH.  In any case, we'll look for the
   real 'chromite/shell/main.py' based on the environment variable
   CROS_WORKON_SRCROOT, so it doesn't matter what the CWD is.
 
 If you're looking at a copy and want to know where the original looks at, look
 here:
   http://git.chromium.org/gitweb/?p=chromite.git;a=blob;f=bin/chromite
 
 Since this script is _copied_, it should remain small and not use internal libs.
+
 """
 
 # Python imports.
 import os
 import sys
 
-if __name__ == '__main__':
-  # Look relative to CROS_WORKON_SRCROOT if that variable exists.  This is
-  # the "inside the chroot" case.
-  if 'CROS_WORKON_SRCROOT' in os.environ:
-    chromite_path = os.path.join(os.environ['CROS_WORKON_SRCROOT'],
-                                 'chromite', 'shell', 'main.py')
-    if os.path.isfile(chromite_path):
-      # Exec the script, which will never return.
-      os.execv(chromite_path, sys.argv)
-    else:
-      print (
-          "ERROR: Couldn't find the chromite tool.\n"
-          "\n"
-          "You may need to update your chroot.  If you need help, see:\n"
-          "  http://www.chromium.org/chromium-os/developer-guide"
-      )
-      sys.exit(1)
+def Search(path):
+  """Return an iterator of places to look for chromite."""
 

[diandersAtChromium, 2011/02/03 00:44:22]

Please make it so that if chromite is already in the sys.path that we use that
one.  Don't always add CROS_WORKON_SRCROOT before trying the first import.  That
way, if importing chromite works w/out any path modifications then we don't add
SRCROOT to the sys.path.  This make it so that we can't treat other dirs
directly in SRCROOT as python libraries.

[Kenneth Waters, 2011/02/03 18:16:41]

jrbarnette wanted it this way.

[diandersAtChromium, 2011/02/03 18:36:01]

Talked to jrbarnette.  You can push this CL as is.  

I will submit a future CL that will detect if we're in the chroot (via existence
of /etc/debian_chroot).  If we're in the chroot, we'll do the "yield []" as the
first thing.  Else we won't do the "yield []".

-  # Outside the chroot, search upward until the "parent" dir doesn't change
-  # (on Linux, that means we're at '/').  That is an error case.
-  dir = os.getcwd()
-  prev_dir = None
-  while dir != prev_dir:
-    chromite_path = os.path.join(dir, 'chromite', 'shell', 'main.py')
-    if os.path.isfile(chromite_path):
-      # Add the directory above chromite to PYTHONPATH before executing, so
-      # that "import chromite.abc.xyz" works...
-      env = os.environ.copy()
-      if 'PYTHONPATH' in env:
-        env['PYTHONPATH'] += ':%s' % dir
-      else:
-        env['PYTHONPATH'] = dir
+  # Look in $CROS_WORKON_SRCROOT first.
+  yield os.environ.get('CROS_WORKON_SRCROOT', '')
 
-      # Exec the script, which will never return.
-      os.execve(chromite_path, sys.argv, env)
+  # Search upward until we either end up with a blank dir or the "parent" dir
+  # doesn't change.
+  prev_path = None
+  while path and path != prev_path:
+    yield path
+    path, prev_path = os.path.dirname(path), path
 
-    prev_dir = dir
-    dir = os.path.dirname(dir)
 
+sys.path.insert(0, '')

[diandersAtChromium, 2011/02/03 00:44:22]

Please don't add ever '' into the path.  This makes things fail if the CWD of
the user happens to have a folder called 'chromite'.

Since we still have an old version of 'chromite' in 'src/scripts', it means that
this script will fail if the user's CWD happens to be src/scripts.

[Kenneth Waters, 2011/02/03 18:16:41]

I was partially confused by by what interactive python does.

It's worse that that because of the way search works it fails if your CWD is
anywhere below scripts/.  I've made it more robust.

+for path in Search(os.getcwd()):
+  sys.path[0] = path
+  try:
+    import chromite.shell.main
+    break
+  except ImportError:
+    pass
+else:
   # TODO(dianders): Should we actually print out the 'repo init' call that
   # the user should use?
-  print (
+  sys.stderr.write(
       "ERROR: Couldn't find the chromite tool.\n"
       "\n"
       "Please change to a directory inside your Chromium OS source tree\n"
       "and retry.  If you need to setup a Chromium OS source tree, see:\n"
-      "  http://www.chromium.org/chromium-os/developer-guide"
-  )
+      "  http://www.chromium.org/chromium-os/developer-guide\n")
   sys.exit(1)
+
+chromite.shell.main.main()
+sys.exit(0)

[diandersAtChromium, 2011/02/03 00:44:22]

Can we remove this sys.exit(0)?  ...if not, can you add a comment about why it's
needed?

[Kenneth Waters, 2011/02/03 18:16:41]

legacy.  removed.