Docserver: Pull knowledge of host file systems into a single

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

Index: chrome/common/extensions/docs/server2/host_file_system_provider.py
diff --git a/chrome/common/extensions/docs/server2/host_file_system_creator.py b/chrome/common/extensions/docs/server2/host_file_system_provider.py
similarity index 64%
rename from chrome/common/extensions/docs/server2/host_file_system_creator.py
rename to chrome/common/extensions/docs/server2/host_file_system_provider.py
index cf741058ca9b6bec371bd768c076d0f655fb7902..a205e2ab63dd72abfbc44c77435f4f2e54ce9be2 100644
--- a/chrome/common/extensions/docs/server2/host_file_system_creator.py
+++ b/chrome/common/extensions/docs/server2/host_file_system_provider.py
@@ -6,14 +6,19 @@ from caching_file_system import CachingFileSystem
 from local_file_system import LocalFileSystem
 from offline_file_system import OfflineFileSystem
 from subversion_file_system import SubversionFileSystem
+from third_party.json_schema_compiler.memoize import memoize
 
-class HostFileSystemCreator(object):
+# TODO(kalman): Rename this HostFileSystemProvider.
+
+class HostFileSystemProvider(object):
   '''Creates host file systems with configuration information. By default, SVN
   file systems are created, although a constructor method can be passed in to
   override this behavior (likely for testing purposes).
   '''
   def __init__(self,
                object_store_creator,
+               revision_for_trunk=None,
+               trunk=None,
                offline=False,
                constructor_for_test=None):
     self._object_store_creator = object_store_creator
@@ -22,19 +27,39 @@ class HostFileSystemCreator(object):
     self._offline = offline
     # Provides custom create behavior, useful in tests.
     self._constructor_for_test = constructor_for_test
+    # Common case is for trunk to be derived from the 'trunk' branch, but we
+    # need to allow overriding that for cases like pinning trunk to a specific
+    # revision and patched file systems.
+    if trunk is not None:
+      assert revision_for_trunk is None, \
+             'Cannot specify both revision_for_trunk= and trunk='
+      self._trunk = trunk
+    else:
+      self._trunk = self._Create('trunk', revision=revision_for_trunk)
 
-  def Create(self, branch='trunk', revision=None, offline=None):
+  @memoize
+  def GetTrunk(self, revision=None):
+    return (self._trunk if revision is None else
+            self._Create('trunk', revision=revision))
+
+  @memoize
+  def GetBranch(self, branch):
     '''Creates either SVN file systems or specialized file systems from the
     constructor passed into this instance. Wraps the resulting file system in
     an Offline file system if the offline flag is set, and finally wraps it in a
     Caching file system.
     '''
+    assert isinstance(branch, basestring), 'Branch %s must be a string' % branch
+    assert branch != 'trunk', 'Cannot specify branch=\'trunk\', use GetTrunk()'
+    return self._Create(branch)
+
+  def _Create(self, branch, revision=None):
     if self._constructor_for_test is not None:
       file_system = self._constructor_for_test(branch=branch, revision=revision)
     else:
       file_system = SubversionFileSystem.Create(branch=branch,
                                                 revision=revision)
-    if offline or (offline is None and self._offline):
+    if self._offline:
       file_system = OfflineFileSystem(file_system)
     return CachingFileSystem(file_system, self._object_store_creator)
 
@@ -42,16 +67,16 @@ class HostFileSystemCreator(object):
   def ForLocal(object_store_creator):
     '''Used in creating a server instance on localhost.
     '''
-    return HostFileSystemCreator(
+    return HostFileSystemProvider(
         object_store_creator,
         constructor_for_test=lambda **_: LocalFileSystem.Create())
 
   @staticmethod
   def ForTest(file_system, object_store_creator):
-    '''Used in creating a test server instance. The HostFileSystemCreator
+    '''Used in creating a test server instance. The HostFileSystemProvider
     returned here will always return |file_system| when its Create() method is
     called.
     '''
-    return HostFileSystemCreator(
+    return HostFileSystemProvider(
         object_store_creator,
         constructor_for_test=lambda **_: file_system)