Refactor the devserver to make it easier to control caching

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

 # Copyright (c) 2012 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.
 
 import os
 from io import BytesIO
 import re
 from zipfile import ZipFile
 
 import compiled_file_system as compiled_fs
 
+# Increment this if the data model changes for ExampleZipper.
+_VERSION = 1
+
 class ExampleZipper(object):
   """This class creates a zip file given a samples directory.
   """
-  def __init__(self, file_system, cache_factory, base_path):
-    self._base_path = base_path
-    self._zip_cache = cache_factory.Create(self._MakeZipFile,
-                                           compiled_fs.ZIP)
+  def __init__(self, file_system, compiled_fs_factory, base_path):
+    self._base_path = base_path.rstrip('/')
+    self._zip_cache = compiled_fs_factory.Create(self._MakeZipFile,
+                                                 ExampleZipper,
+                                                 version=_VERSION)
     self._file_system = file_system
 
   def _MakeZipFile(self, base_dir, files):
-    zip_path = os.path.commonprefix(files).rsplit('/', 1)[-2]
-    prefix = zip_path.rsplit('/', 1)[-2]
-    if zip_path + '/manifest.json' not in files:
+    if 'manifest.json' not in files:
       return None
     zip_bytes = BytesIO()
     zip_file = ZipFile(zip_bytes, mode='w')
     try:
       for name, file_contents in (
-          self._file_system.Read(files, binary=True).Get().iteritems()):
-        zip_file.writestr(name[len(prefix):].strip('/'), file_contents)
+          self._file_system.Read(['%s%s' % (base_dir, f) for f in files],
+                                 binary=True).Get().iteritems()):
+        # We want e.g. basic.zip to expand to basic/manifest.json etc, not
+        # chrome/common/extensions/.../basic/manifest.json, so only use the
+        # end of the path component when writing into the zip file.
+        redundant_prefix = '%s/' % base_dir.rstrip('/').rsplit('/', 1)[0]
+        zip_file.writestr(name[len(redundant_prefix):], file_contents)
     finally:
       zip_file.close()
     return zip_bytes.getvalue()
 
   def Create(self, path):
     """ Creates a new zip file from the recursive contents of |path|
     as returned by |_zip_cache|.
     Paths within the zip file are given relative to and including |path|.
     """
     return self._zip_cache.GetFromFileListing(
-        self._base_path + '/' + path)
+        '%s/%s' % (self._base_path, path.strip('/')))