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 local_git_file_system import LocalGitFileSystem
   8 from offline_file_system import OfflineFileSystem
   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 master, 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                pinned_commit=None,
  22                default_master_instance=None,
  23                offline=False,
  24                constructor_for_test=None,
  25                cache_only=False):
  26     '''
  27     |object_store_creator|
  28       Provides caches for file systems that need one.
  29     |pinned_commit|
  30       If not None, the commit at which a 'master' file system will be created.
  31       If None, 'master' file systems will use HEAD.
  32     |default_master_instance|
  33       If not None, 'master' file systems provided by this class without a
  34       specific commit will return |default_master_instance| instead.
  35     |offline|
  36       If True all provided file systems will be wrapped in an OfflineFileSystem.
  37     |constructor_for_test|
  38       Provides a custom constructor rather than creating LocalGitFileSystems.
  39     |cache_only|
  40       If True, all provided file systems will be cache-only, meaning that cache
  41       misses will result in errors rather than cache updates.
  42     '''
  43     self._object_store_creator = object_store_creator
  44     self._pinned_commit = pinned_commit
  45     self._default_master_instance = default_master_instance
  46     self._offline = offline
  47     self._constructor_for_test = constructor_for_test
  48     self._cache_only = cache_only
  49
  50   @memoize
  51   def GetMaster(self, commit=None):
  52     '''Gets a file system tracking 'master'. Use this method rather than
  53     GetBranch('master') because the behaviour is subtly different; 'master' can
  54     be pinned to a specific commit (|pinned_commit| in constructor) and can have
  55     have its default instance overridden (|default_master_instance| in the
  56     constructor).
  57
  58     |commit| if non-None determines a specific commit to pin the host file
  59     system at, though it will be ignored if it's newer than |pinned_commit|.
  60     If None then |commit| will track |pinned_commit| if is has been
  61     set, or just HEAD (which might change during server runtime!).
  62     '''
  63     if commit is None:
  64       if self._default_master_instance is not None:
  65         return self._default_master_instance
  66       return self._Create('master', commit=self._pinned_commit)
  67     return self._Create('master', commit=commit)
  68
  69   @memoize
  70   def GetBranch(self, branch):
  71     '''Gets a file system tracking |branch|, for example '1150' - anything other
  72     than 'master', which must be constructed via the GetMaster() method.
  73
  74     Note: Unlike GetMaster this function doesn't take a |commit| argument
  75     since we assume that branches hardly ever change, while master frequently
  76     changes.
  77     '''
  78     assert isinstance(branch, basestring), 'Branch %s must be a string' % branch
  79     assert branch != 'master', (
  80         'Cannot specify branch=\'master\', use GetMaster()')
  81     return self._Create(branch)
  82
  83   def _Create(self, branch, commit=None):
  84     '''Creates local git file systems (or if in a test, potentially whatever
  85     |self._constructor_for_test specifies). Wraps the resulting file system in
  86     an Offline file system if the offline flag is set, and finally wraps it in
  87     a Caching file system.
  88     '''
  89     if self._constructor_for_test is not None:
  90       file_system = self._constructor_for_test(branch=branch, commit=commit)
  91     else:
  92       file_system = LocalGitFileSystem.Create(branch=branch, commit=commit)
  93     if self._offline:
  94       file_system = OfflineFileSystem(file_system)
  95     return CachingFileSystem(file_system, self._object_store_creator,
  96         fail_on_miss=self._cache_only)
  97
  98   @staticmethod
  99   def ForLocal(object_store_creator, **optargs):
 100     '''Used in creating a server instance on localhost.
 101     '''
 102     return HostFileSystemProvider(
 103         object_store_creator,
 104         constructor_for_test=lambda **_: LocalFileSystem.Create(),
 105         **optargs)
 106
 107   @staticmethod
 108   def ForTest(file_system, object_store_creator, **optargs):
 109     '''Used in creating a test server instance. The HostFileSystemProvider
 110     returned here will always return |file_system| when its Create() method is
 111     called.
 112     '''
 113     return HostFileSystemProvider(
 114         object_store_creator,
 115         constructor_for_test=lambda **_: file_system,
 116         **optargs)