Prevent get_archive.py from going into an infinite loop if you request a

tools/get_archive.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # Gets or updates a DumpRenderTree (a nearly headless build of chrome). This is
 # used for running browser tests of client applications.
 
 import json
@@ skipping 143 matching lines @@
         result, out = gsutil('ls', permanent_prefix % {'osname' : osname,
             'num1': '*', 'num2': revision_num })
         if result == 0:
           # First try to find one with the the second number the same as the
           # requested number.
           latest = out.split()[0]
           foundURL = True
         else:
           # Now try to find one with a nearby CL num.
           revision_num = int(revision_num) - 1
+          if revision_num <= 0:
+            too_early_error()
     return latest
     
   get_from_gsutil(name, directory, version_file, latest_pattern, osdict, 
                   find_permanent_url, revision_num)
 
 def get_sdk_revision(name, directory, version_file, latest_pattern,
     permanent_prefix, revision_num):
   """Get a revision of the SDK from the editor build archive.
 
   Args:
@@ skipping 105 matching lines @@
     shutil.rmtree(temp_dir)
 
   # create the version stamp
   v = open(version_file, 'w')
   v.write(latest)
   v.close()
 
   print 'Successfully downloaded to %s' % directory
   return 0
 
+def too_early_error():
+  """Quick shortcutting function, to return early if someone requests a revision
+  that is smaller than the earliest stored. This saves us from doing repeated
+  requests until we get down to 0."""
+  print ('Unable to download requested revision because it is earlier than the '
+      'earliest revision stored.')
+  sys.exit(1)
 
 def main():
   parser = optparse.OptionParser(usage='usage: %prog [options] download_name')
   parser.add_option('-r', '--revision', dest='revision',
                     help='Desired revision number to retrieve for the SDK. If '
                     'unspecified, retrieve the latest SDK build.',
                     action='store', default=None)
   args, positional = parser.parse_args()
 
   if positional[0] == 'dartium':
+    if args.revision < 4285:

[Emily Fortuna, 2012/08/17 19:52:02]

I'm not a fan of hard-coding the "earliest revision" numbers, but this saves us
from making, in this case 4285 requests (and in some cases 9761 requests!) to
determine that no earlier version exists. I'm certainly open to any suggested
nicer solution.

+      return too_early_error()
     get_dartium_revision('Dartium', DARTIUM_DIR, DARTIUM_VERSION,
                          DARTIUM_LATEST_PATTERN, DARTIUM_PERMANENT_PATTERN,
                          args.revision)
   elif positional[0] == 'chromedriver':
+    if args.revision < 7823:
+      return too_early_error()
     get_dartium_revision('chromedriver', CHROMEDRIVER_DIR, CHROMEDRIVER_VERSION,
                          CHROMEDRIVER_LATEST_PATTERN,
                          CHROMEDRIVER_PERMANENT_PATTERN, args.revision)
   elif positional[0] == 'sdk':
+    if args.revision < 9761:
+      return too_early_error()
     get_sdk_revision('sdk', SDK_DIR, SDK_VERSION, SDK_LATEST_PATTERN,
         SDK_PERMANENT, args.revision)
   elif positional[0] == 'drt':
+    if args.revision < 5342:
+      return too_early_error()
     get_dartium_revision('DumpRenderTree', DRT_DIR, DRT_VERSION,
                          DRT_LATEST_PATTERN, DRT_PERMANENT_PATTERN,
                          args.revision)
   else:
     print ('Please specify the target you wish to download from Google Storage '
         '("drt", "dartium", "chromedriver", or "sdk")')
 
 if __name__ == '__main__':
   sys.exit(main())