[Extension DocServer] Update BranchUtility, README

chrome/common/extensions/docs/server2/branch_utility.py

 # 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.
 
 import json
 import logging
 import operator
 
 from environment_wrappers import CreateUrlFetcher
 import url_constants
@@ skipping 74 matching lines @@
       if channel_info.version < stable_info.version:
         return self.GetStableChannelInfo(channel_info.version + 1)
     names = self.GetAllChannelNames()
     return self.GetAllChannelInfo()[names.index(channel_info.channel) + 1]
 
   def Older(self, channel_info):
     '''Given a ChannelInfo object, returns a new ChannelInfo object
     representing the previous Chrome version/branch combination.
     '''
     if channel_info.channel == 'stable':
-      if channel_info.version <= 5:
-        # BranchUtility can't access branch data from before Chrome version 5.
-        return None
       return self.GetStableChannelInfo(channel_info.version - 1)
     names = self.GetAllChannelNames()
     return self.GetAllChannelInfo()[names.index(channel_info.channel) - 1]
 
   @staticmethod
   def SplitChannelNameFromPath(path):
     '''Splits the channel name out of |path|, returning the tuple
     (channel_name, real_path). If the channel cannot be determined then returns
     (None, path).
     '''
@@ skipping 23 matching lines @@
     if version != 'master':
       version = int(version)
     return ChannelInfo(channel,
                        self._ExtractFromVersionJson(channel, 'branch'),
                        version)
 
   def GetStableChannelInfo(self, version):
     '''Given a |version| corresponding to a 'stable' version of Chrome, returns
     a ChannelInfo object representing that version.
     '''
-    return ChannelInfo('stable', self.GetBranchForVersion(version), version)
+    branch = self.GetBranchForVersion(version)
+    if branch is None:
+      return None
+    return ChannelInfo('stable', branch, version)
 
   def _ExtractFromVersionJson(self, channel_name, data_type):
     '''Returns the branch or version number for a channel name.
     '''
     if channel_name == 'master':
       return 'master'
 
     if data_type == 'branch':
       object_store = self._branch_object_store
     elif data_type == 'version':
@@ skipping 41 matching lines @@
     if version == 'master':
       return 'master'
 
     branch = self._branch_object_store.Get(str(version)).Get()
     if branch is not None:
       return branch
 
     version_json = json.loads(self._history_result.Get().content)
     for entry in version_json:
       version_title = entry['version'].split('.')
+      # TODO(devlin): Is there a reason we don't cache all these values now?
       if version_title[0] == str(version):
         self._branch_object_store.Set(str(version), version_title[2])
         return version_title[2]
 
-    raise ValueError('The branch for %s could not be found.' % version)
+    # This can legitimately happen because
+    # https://omahaproxy.appspot.com/history.json?channel=dev&os=win&json=1
+    # (where we get the branch data) has a maximum number of results. The
+    # assertion is a nasty hack to make sure that we're at least retrieving
+    # a reasonable number of version. Unfortunately, this is also doomed to
+    # need updating every five years or so.
+    # TODO(devlin): Really, this is awful.
+    assert(version < 40)
+    return None
 
   def GetChannelForVersion(self, version):
     '''Returns the name of the development channel corresponding to a given
     version number.
     '''
     for channel_info in self.GetAllChannelInfo():
       if channel_info.channel == 'stable' and version <= channel_info.version:
         return channel_info.channel
       if version == channel_info.version:
         return channel_info.channel
 
   def GetLatestVersionNumber(self):
     '''Returns the most recent version number found using data stored on
     omahaproxy.
     '''
     latest_version = self._version_object_store.Get('latest').Get()
     if latest_version is not None:
       return latest_version
 
     version_json = json.loads(self._history_result.Get().content)
     latest_version = 0
     for entry in version_json:
       version_title = entry['version'].split('.')
       version = int(version_title[0])
       if version > latest_version:
         latest_version = version
 
     self._version_object_store.Set('latest', latest_version)
     return latest_version