Docserver: Add support for viewing docs with a codereview patch applied

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

+# Copyright 2013 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.
+
+from file_system import FileSystem, StatInfo, FileNotFoundError
+from future import Future
+import logging
+
+class _AsyncFetchFuture(object):
+  def __init__(self, paths, binary, svn_future, patched_future):
+    self._svn_future = svn_future
+    self._patched_future = patched_future
+
+  def Get(self):
+    value = self._svn_future.Get()
+    value.update(self._patched_future.Get())
+    return value
+
+class PatchedFileSystem(FileSystem):
+  """ Class to fetch resources with a patch applied.
+  """
+  def __init__(self, patched_files, svn_file_system, patch_file_system):
+    self._patched_files = patched_files
+    self._svn_file_system = svn_file_system
+    self._patch_file_system = patch_file_system
+
+  def Read(self, paths, binary=False):
+    # TODO(fj): What about directory listing?

[方觉(Fang Jue), 2013/04/29 12:46:23]

I found that directory listing is used in APIListDataSource (and probably
somewhere else). If a file for an API is removed, it still appears in chrome.*
API page (for example,
https://chrome-apps-doc-test.appspot.com/_patch/14096030/extensions/api_index...
. runtime.html was removed in that patch.). It isn't a big problem though.

[not at google - send to devlin, 2013/04/29 16:38:49]

Do you mean normally? As in the server right now, if a file is removed then it
still shows up in the API list? Or is this something that is specific to the
patched file system (I presume the former).

We should at least fix that at some point.

[方觉(Fang Jue), 2013/04/30 01:07:11]

It's specific to the patched file system. When fetching directory listing, the
path ends with '/'. No path in patched_files will end with '/'. Therefore it
will eventually directly call svn_file_system's Read.

+    patched_paths = list(set(paths) & set(self._patched_files))
+    unpatched_paths = list(set(paths) - set(self._patched_files))
+    return Future(delegate=_AsyncFetchFuture(
+        paths,
+        binary,
+        self._svn_file_system.Read(unpatched_paths, binary),
+        self._patch_file_system.Read(patched_paths, binary)))
+
+  def _FindChildren(self, path):
+    children = []
+    for p in self._patched_files:
+      if p.startswith(path):
+        child = p.split(path, 1)[1]
+        if '/' in child:
+          child = child.split('/', 1)[0] + '/'
+        children.append(child)
+    return children
+
+  # Create dummy stat info for added files in a patch.
+  def _TryCreateStatInfo(self, path):
+    if path.endswith('/'):
+      children = self._FindChildren(path)
+      if len(children) == 0:
+        return None
+      return StatInfo('0', {child: '0' for child in children})
+    elif path in self._patched_files:
+      return StatInfo('0', {})
+    else:
+      return None
+
+  # We assume that a patchset, once created, will never change. For any new
+  # files, returned version will be '0'. Different patchesets will have
+  # separate caches so they won't interfere with each other even if versions
+  # are all '0'.

[not at google - send to devlin, 2013/04/29 16:38:49]

I was thinking about this more and we shouldn't be re-creating these for each
patchset that gets uploaded.

[方觉(Fang Jue), 2013/04/30 14:25:08]

Done.

+  def Stat(self, path):
+    try:
+      stat_info = self._svn_file_system.Stat(path)
+      if stat_info.child_versions:
+        # New files can be added to the directory in the patch
+        added_children = (set(self._FindChildren(path)) -
+            set(stat_info.child_versions.keys()))
+        stat_info.child_versions.update(
+            {child: '0' for child in added_children})
+    except FileNotFoundError as e:
+      # Try to create a dummy stat if a new file/directory is added.
+      stat_info = self._TryCreateStatInfo(path)
+      if stat_info is None:
+        raise e
+    return stat_info