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

   1 # Copyright 2013 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 from caching_file_system import CachingFileSystem
   6 from local_file_system import LocalFileSystem
   7 from offline_file_system import OfflineFileSystem
   8 from subversion_file_system import SubversionFileSystem
   9 from third_party.json_schema_compiler.memoize import memoize
  10
  11
  12 class HostFileSystemProvider(object):
  13   '''Provides host file systems ("host" meaning the file system that hosts the
  14   server's source code and templates) tracking trunk, or any branch.
  15
  16   File system instances are memoized to maintain the in-memory caches across
  17   multiple callers.
  18   '''
  19   def __init__(self,
  20                object_store_creator,
  21                max_trunk_revision=None,
  22                default_trunk_instance=None,
  23                offline=False,
  24                constructor_for_test=None):
  25     '''
  26     |object_store_creator|
  27       Provides caches for file systems that need one.
  28     |max_trunk_revision|
  29       If not None, the maximum revision that a 'trunk' file system will be
  30       created at. If None, 'trunk' file systems will use HEAD.
  31     |default_trunk_instance|
  32       If not None, 'trunk' file systems provided by this class without a
  33       specific revision will return |default_trunk_instance| instead.
  34     |offline|
  35       If True all provided file systems will be wrapped in an OfflineFileSystem.
  36     |constructor_for_test|
  37       Provides a custom constructor rather than creating SubversionFileSystems.
  38     '''
  39     self._object_store_creator = object_store_creator
  40     self._max_trunk_revision = max_trunk_revision
  41     self._default_trunk_instance = default_trunk_instance
  42     self._offline = offline
  43     self._constructor_for_test = constructor_for_test
  44
  45   @memoize
  46   def GetTrunk(self, revision=None):
  47     '''Gets a file system tracking 'trunk'. Use this method rather than
  48     GetBranch('trunk') because the behaviour is subtly different; 'trunk' can
  49     be pinned to a max revision (|max_trunk_revision| in constructor) and can
  50     have its default instance overridden (|default_trunk_instance| in
  51     constructor).
  52
  53     |revision| if non-None determines a specific revision to pin the host file
  54     system at, though it will be ignored if it exceeds |max_trunk_revision|.
  55     If None then |revision| will track |max_trunk_revision| if is has been
  56     set, or just HEAD (which might change during server runtime!).
  57     '''
  58     if revision is None:
  59       if self._default_trunk_instance is not None:
  60         return self._default_trunk_instance
  61       return self._Create('trunk', revision=self._max_trunk_revision)
  62     if self._max_trunk_revision is not None:
  63       revision = min(revision, self._max_trunk_revision)
  64     return self._Create('trunk', revision=revision)
  65
  66   @memoize
  67   def GetBranch(self, branch):
  68     '''Gets a file system tracking |branch|, for example '1150' - anything other
  69     than 'trunk', which must be constructed via the GetTrunk() method.
  70
  71     Note: Unlike GetTrunk this function doesn't take a |revision| argument
  72     since we assume that branches hardly ever change, while trunk frequently
  73     changes.
  74     '''
  75     assert isinstance(branch, basestring), 'Branch %s must be a string' % branch
  76     assert branch != 'trunk', 'Cannot specify branch=\'trunk\', use GetTrunk()'
  77     return self._Create(branch)
  78
  79   def _Create(self, branch, revision=None):
  80     '''Creates SVN file systems (or if in a test, potentially whatever
  81     |self._constructor_for_test specifies). Wraps the resulting file system in
  82     an Offline file system if the offline flag is set, and finally wraps it in
  83     a Caching file system.
  84     '''
  85     if self._constructor_for_test is not None:
  86       file_system = self._constructor_for_test(branch=branch, revision=revision)
  87     else:
  88       file_system = SubversionFileSystem.Create(branch=branch,
  89                                                 revision=revision)
  90     if self._offline:
  91       file_system = OfflineFileSystem(file_system)
  92     return CachingFileSystem(file_system, self._object_store_creator)
  93
  94   @staticmethod
  95   def ForLocal(object_store_creator, **optargs):
  96     '''Used in creating a server instance on localhost.
  97     '''
  98     return HostFileSystemProvider(
  99         object_store_creator,
 100         constructor_for_test=lambda **_: LocalFileSystem.Create(),
 101         **optargs)
 102
 103   @staticmethod
 104   def ForTest(file_system, object_store_creator, **optargs):
 105     '''Used in creating a test server instance. The HostFileSystemProvider
 106     returned here will always return |file_system| when its Create() method is
 107     called.
 108     '''
 109     return HostFileSystemProvider(
 110         object_store_creator,
 111         constructor_for_test=lambda **_: file_system,
 112         **optargs)