Docserver: Make MockFileSystem not iterate over the entire file system as part

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

Index: chrome/common/extensions/docs/server2/mock_file_system.py
diff --git a/chrome/common/extensions/docs/server2/mock_file_system.py b/chrome/common/extensions/docs/server2/mock_file_system.py
index 145151d61148920f41b8f7d70131a530c3ba7ea9..883a14b2183631e102595d84f3716d8c2ea09a23 100644
--- a/chrome/common/extensions/docs/server2/mock_file_system.py
+++ b/chrome/common/extensions/docs/server2/mock_file_system.py
@@ -2,22 +2,25 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import posixpath
+
 from file_system import FileSystem, FileNotFoundError
 from future import Gettable, Future
-from test_file_system import TestFileSystem
+from test_file_system import _List, _StatTracker, TestFileSystem
+
 
 class MockFileSystem(FileSystem):
   '''Wraps FileSystems to add a selection of mock behaviour:
-
   - asserting how often Stat/Read calls are being made to it.
   - primitive changes/versioning via applying object "diffs", mapping paths to
     new content (similar to how TestFileSystem works).
   '''
   def __init__(self, file_system):
     self._file_system = file_system
-    # Updates are modelled are stored as TestFileSystems because they've
-    # implemented a bunch of logic to interpret paths into dictionaries.
+    # Updates are stored as TestFileSystems because it already implements a
+    # bunch of logic to intepret paths into dictionaries.
     self._updates = []
+    self._stat_tracker = _StatTracker()
     self._read_count = 0
     self._read_resolve_count = 0
     self._stat_count = 0
@@ -43,7 +46,7 @@ class MockFileSystem(FileSystem):
       self._read_resolve_count += 1
       result = future_result.Get()
       for path in result.iterkeys():
-        _, update = self._GetMostRecentUpdate(path)
+        update = self._GetMostRecentUpdate(path)
         if update is not None:
           result[path] = update
       return result
@@ -53,38 +56,34 @@ class MockFileSystem(FileSystem):
     return self._file_system.Refresh()
 
   def _GetMostRecentUpdate(self, path):
-    for revision, update in reversed(list(enumerate(self._updates))):
+    '''Returns the latest update for the file at |path|, or None if |path|
+    has never been updated.
+    '''
+    for update in reversed(self._updates):
       try:
-        return (revision + 1, update.ReadSingle(path).Get())
+        return update.ReadSingle(path).Get()
       except FileNotFoundError:
         pass
-    return (0, None)
+    return None
 
   def Stat(self, path):
     self._stat_count += 1
-    return self._StatImpl(path)
-
-  def _StatImpl(self, path):
-    result = self._file_system.Stat(path)
-    result.version = self._UpdateStat(result.version, path)
-    child_versions = result.child_versions
-    if child_versions is not None:
-      for child_path in child_versions.iterkeys():
-        child_versions[child_path] = self._UpdateStat(
-            child_versions[child_path],
-            '%s%s' % (path, child_path))
-    return result
-
-  def _UpdateStat(self, version, path):
-    if not path.endswith('/'):
-      return str(int(version) + self._GetMostRecentUpdate(path)[0])
-    # Bleh, it's a directory, need to recursively search all the children.
-    child_paths = self._file_system.ReadSingle(path).Get()
-    if not child_paths:
-      return version
-    return str(max([int(version)] +
-                   [int(self._StatImpl('%s%s' % (path, child_path)).version)
-                    for child_path in child_paths]))
+
+    # This only supports numeric stat values since we need to add to it.  In
+    # reality the logic here could just be to randomly mutate the stat values
+    # every time there's an Update but that's less meaningful for testing.
+    def stradd(a, b):
+      return str(int(a) + b)
+
+    stat = self._file_system.Stat(path)
+    stat.version = stradd(stat.version, self._stat_tracker.GetVersion(path))
+    if stat.child_versions:
+      for child_path, child_version in stat.child_versions.iteritems():
+        stat.child_versions[child_path] = stradd(
+            stat.child_versions[child_path],
+            self._stat_tracker.GetVersion(posixpath.join(path, child_path)))
+
+    return stat
 
   def GetIdentity(self):
     return self._file_system.GetIdentity()
@@ -126,3 +125,8 @@ class MockFileSystem(FileSystem):
 
   def Update(self, update):
     self._updates.append(TestFileSystem(update))
+    for path in _List(update).iterkeys():
+      # Any files (not directories) which changed are now at the version
+      # derived from |_updates|.
+      if path != '' and not path.endswith('/'):
+        self._stat_tracker.SetVersion(path, len(self._updates))