tools/android/aar_resources_extractor.py

# Lint as: python2, python3
# pylint: disable=g-direct-third-party-import
# Copyright 2017 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""A tool for extracting resource files from an AAR.

An AAR may contain resources under the /res directory. This tool extracts all
of the resources into a directory. If no resources exist, it creates an
empty.xml file that defines no resources.

In the future, this script may be extended to also extract assets.
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import os
import sys
import zipfile

# Do not edit this line. Copybara replaces it with PY2 migration helper.
from absl import app
from absl import flags
import six

from tools.android import junction

FLAGS = flags.FLAGS

flags.DEFINE_string("input_aar", None, "Input AAR")
flags.mark_flag_as_required("input_aar")
flags.DEFINE_string("output_res_dir", None, "Output resources directory")
flags.mark_flag_as_required("output_res_dir")
flags.DEFINE_string("output_assets_dir", None, "Output assets directory")


def ExtractResources(aar, output_res_dir):
  """Extract resource from an `aar` file to the `output_res_dir` directory."""
  aar_contains_no_resources = True
  output_res_dir_abs = os.path.abspath(output_res_dir)
  for name in aar.namelist():
    if name.startswith("res/") and not name.endswith("/"):
      ExtractOneFile(aar, name, output_res_dir_abs)
      aar_contains_no_resources = False
  if aar_contains_no_resources:
    empty_xml_filename = six.ensure_str(
        output_res_dir) + "/res/values/empty.xml"
    WriteFileWithJunctions(empty_xml_filename, b"<resources/>")


def ExtractAssets(aar, output_assets_dir):
  """Extracts assets from an `aar` file to the `output_assets_dir` directory."""
  aar_contains_no_assets = True
  output_assets_dir_abs = os.path.abspath(output_assets_dir)
  for name in aar.namelist():
    if name.startswith("assets/") and not name.endswith("/"):
      ExtractOneFile(aar, name, output_assets_dir_abs)
      aar_contains_no_assets = False
  if aar_contains_no_assets:
    # aapt will ignore this file and not print an error message, because it
    # thinks that it is a swap file. We need to create at least one file so that
    # Bazel does not complain that the output tree artifact was not created.
    empty_asset_filename = (
        six.ensure_str(output_assets_dir) +
        "/assets/empty_asset_generated_by_bazel~")
    WriteFileWithJunctions(empty_asset_filename, b"")


def WriteFileWithJunctions(filename, content):
  """Writes file including creating any junctions or directories necessary."""
  def _WriteFile(filename):
    with open(filename, "wb") as openfile:
      openfile.write(content)

  if os.name == "nt":
    # Create a junction to the parent directory, because its path might be too
    # long. Creating the junction also creates all parent directories.
    with junction.TempJunction(os.path.dirname(filename)) as junc:
      filename = os.path.join(junc, os.path.basename(filename))
      # Write the file within scope of the TempJunction, otherwise the path in
      # `filename` would no longer be valid.
      _WriteFile(filename)
  else:
    os.makedirs(os.path.dirname(filename))
    _WriteFile(filename)


def ExtractOneFile(aar, name, abs_output_dir):
  """Extract one file from the aar to the output directory."""
  if os.name == "nt":
    fullpath = os.path.normpath(os.path.join(abs_output_dir, name))
    if name[-1] == "/":
      # The zip entry is a directory. Create a junction to it, which also
      # takes care of creating the directory and all of its parents in a
      # longpath-safe manner.
      # We must pretend to have extracted this directory, even if it's
      # empty, therefore we mustn't rely on creating it as a parent
      # directory of a subsequently extracted zip entry (because there may
      # be no such subsequent entry).
      with junction.TempJunction(fullpath.rstrip("/")) as juncpath:
        pass
    else:
      # The zip entry is a file. Create a junction to its parent directory,
      # then open the compressed entry as a file object, so we can extract
      # the data even if the extracted file's path would be too long.
      # The tradeoff is that we lose the permission bits of the compressed
      # file, but Unix permissions don't mean much on Windows anyway.
      with junction.TempJunction(os.path.dirname(fullpath)) as juncpath:
        extracted_path = os.path.join(juncpath, os.path.basename(fullpath))
        with aar.open(name) as src_fd:
          with open(extracted_path, "wb") as dest_fd:
            dest_fd.write(src_fd.read())
  else:
    aar.extract(name, abs_output_dir)


def main(unused_argv):
  with zipfile.ZipFile(FLAGS.input_aar, "r") as aar:
    ExtractResources(aar, FLAGS.output_res_dir)
    if FLAGS.output_assets_dir is not None:
      ExtractAssets(aar, FLAGS.output_assets_dir)

if __name__ == "__main__":
  FLAGS(sys.argv)
  app.run(main)