tools/gn2bp/gen_android_bp

#!/usr/bin/env python3
# Copyright (C) 2022 The Android Open Source Project
#
# 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.

# This tool translates a collection of BUILD.gn files into a mostly equivalent
# Android.bp file for the Android Soong build system. The input to the tool is a
# JSON description of the GN build definition generated with the following
# command:
#
#   gn desc out --format=json --all-toolchains "//*" > desc.json
#
# The tool is then given a list of GN labels for which to generate Android.bp
# build rules. The dependencies for the GN labels are squashed to the generated
# Android.bp target, except for actions which get their own genrule. Some
# libraries are also mapped to their Android equivalents -- see |builtin_deps|.

import argparse
import collections
import json
import logging as log
import operator
import os
import re
import sys
import copy

import gn_utils

ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

# Default targets to translate to the blueprint file.
default_targets = [
    '//components/cronet/android:cronet',
    '//components/cronet:cronet_package',
]

# Defines a custom init_rc argument to be applied to the corresponding output
# blueprint target.
target_initrc = {
    # TODO: this can probably be removed.
}

target_host_supported = [
    # TODO: remove if this is not useful for the cronet build.
]

# Proto target groups which will be made public.
proto_groups = {
    # TODO: remove if this is not used for the cronet build.
}

# All module names are prefixed with this string to avoid collisions.
module_prefix = 'cronet_aml_'

# Shared libraries which are directly translated to Android system equivalents.
shared_library_allowlist = [
    'android',
    'android.hardware.atrace@1.0',
    'android.hardware.health@2.0',
    'android.hardware.health-V1-ndk',
    'android.hardware.power.stats@1.0',
    "android.hardware.power.stats-V1-cpp",
    'base',
    'binder',
    'binder_ndk',
    'cutils',
    'hidlbase',
    'hidltransport',
    'hwbinder',
    'incident',
    'log',
    'services',
    'statssocket',
    "tracingproxy",
    'utils',
]

# Static libraries which are directly translated to Android system equivalents.
static_library_allowlist = [
    'statslog_perfetto',
]

# Include directories that will be removed from all targets.
local_include_dirs_denylist = [
]

# Name of the module which settings such as compiler flags for all other
# modules.
defaults_module = module_prefix + 'defaults'

# Location of the project in the Android source tree.
tree_path = 'external/chromium_org'

# Path for the protobuf sources in the standalone build.
buildtools_protobuf_src = '//buildtools/protobuf/src'

# Location of the protobuf src dir in the Android source tree.
android_protobuf_src = 'external/protobuf/src'

# Compiler flags which are passed through to the blueprint.
cflag_allowlist = [
  # needed for zlib:zlib
  "-mpclmul",
  # needed for zlib:zlib
  "-mssse3",
  # needed for zlib:zlib
  "-msse3",
  # needed for zlib:zlib
  "-msse4.2",
]

# Additional arguments to apply to Android.bp rules.
additional_args = {
    # TODO: remove if not needed.
    'cronet_aml_components_cronet_android_cronet': [
        ('linker_scripts', {
            'base/android/library_loader/anchor_functions.lds',
        }),
    ],
    'cronet_aml_net_net': [
        ('export_static_lib_headers', {
            'cronet_aml_net_third_party_quiche_quiche',
            'cronet_aml_crypto_crypto',
        }),
    ],
}

# Android equivalents for third-party libraries that the upstream project
# depends on.
builtin_deps = {
    '//net/tools/root_store_tool:root_store_tool':
        lambda x: None,
}

# Name of tethering apex module
tethering_apex = "com.android.tethering"

# ----------------------------------------------------------------------------
# End of configuration.
# ----------------------------------------------------------------------------


class Error(Exception):
  pass


class ThrowingArgumentParser(argparse.ArgumentParser):

  def __init__(self, context):
    super(ThrowingArgumentParser, self).__init__()
    self.context = context

  def error(self, message):
    raise Error('%s: %s' % (self.context, message))


def write_blueprint_key_value(output, name, value, sort=True):
  """Writes a Blueprint key-value pair to the output"""

  if isinstance(value, bool):
    if value:
      output.append('    %s: true,' % name)
    else:
      output.append('    %s: false,' % name)
    return
  if not value:
    return
  if isinstance(value, set):
    value = sorted(value)
  if isinstance(value, list):
    output.append('    %s: [' % name)
    for item in sorted(value) if sort else value:
      output.append('        "%s",' % item)
    output.append('    ],')
    return
  if isinstance(value, Target):
    value.to_string(output)
    return
  if isinstance(value, dict):
    kv_output = []
    for k, v in value.items():
      write_blueprint_key_value(kv_output, k, v)

    output.append('    %s: {' % name)
    for line in kv_output:
      output.append('    %s' % line)
    output.append('    },')
    return
  output.append('    %s: "%s",' % (name, value))


class Target(object):
  """A target-scoped part of a module"""

  def __init__(self, name):
    self.name = name
    self.srcs = set()
    self.shared_libs = set()
    self.static_libs = set()
    self.whole_static_libs = set()
    self.header_libs = set()
    self.cflags = set()
    self.dist = dict()
    self.strip = dict()
    self.stl = None
    self.cppflags = set()
    self.local_include_dirs = set()
    self.export_system_include_dirs = set()
    self.generated_headers = set()
    self.export_generated_headers = set()

  def to_string(self, output):
    nested_out = []
    self._output_field(nested_out, 'srcs')
    self._output_field(nested_out, 'shared_libs')
    self._output_field(nested_out, 'static_libs')
    self._output_field(nested_out, 'whole_static_libs')
    self._output_field(nested_out, 'header_libs')
    self._output_field(nested_out, 'cflags')
    self._output_field(nested_out, 'stl')
    self._output_field(nested_out, 'dist')
    self._output_field(nested_out, 'strip')
    self._output_field(nested_out, 'cppflags')
    self._output_field(nested_out, 'local_include_dirs')
    self._output_field(nested_out, 'export_system_include_dirs')
    self._output_field(nested_out, 'generated_headers')
    self._output_field(nested_out, 'export_generated_headers')

    if nested_out:
      output.append('    %s: {' % self.name)
      for line in nested_out:
        output.append('    %s' % line)
      output.append('    },')

  def _output_field(self, output, name, sort=True):
    value = getattr(self, name)
    return write_blueprint_key_value(output, name, value, sort)


class Module(object):
  """A single module (e.g., cc_binary, cc_test) in a blueprint."""

  def __init__(self, mod_type, name, gn_target):
    self.type = mod_type
    self.gn_target = gn_target
    self.name = name
    self.srcs = set()
    self.comment = 'GN: ' + gn_target
    self.shared_libs = set()
    self.static_libs = set()
    self.whole_static_libs = set()
    self.runtime_libs = set()
    self.tools = set()
    self.cmd = None
    self.host_supported = False
    self.device_supported = True
    self.vendor_available = False
    self.init_rc = set()
    self.out = set()
    self.export_include_dirs = set()
    self.generated_headers = set()
    self.export_generated_headers = set()
    self.export_static_lib_headers = set()
    self.defaults = set()
    self.cflags = set()
    self.include_dirs = set()
    self.local_include_dirs = set()
    self.header_libs = set()
    self.required = set()
    self.tool_files = set()
    # target contains a dict of Targets indexed by os_arch.
    # example: { 'android_x86': Target('android_x86')
    self.target = dict()
    self.target['android'] = Target('android')
    self.target['android_x86'] = Target('android_x86')
    self.target['android_x86_64'] = Target('android_x86_64')
    self.target['android_arm'] = Target('android_arm')
    self.target['android_arm64'] = Target('android_arm64')
    self.target['host'] = Target('host')
    self.stl = None
    self.cpp_std = None
    self.dist = dict()
    self.strip = dict()
    self.data = set()
    self.apex_available = set()
    self.min_sdk_version = None
    self.proto = dict()
    self.linker_scripts = set()
    # The genrule_XXX below are properties that must to be propagated back
    # on the module(s) that depend on the genrule.
    self.genrule_headers = set()
    self.genrule_srcs = set()
    self.genrule_shared_libs = set()
    self.genrule_header_libs = set()
    self.version_script = None
    self.test_suites = set()
    self.test_config = None
    self.stubs = {}
    self.cppflags = set()
    self.rtti = False
    # Name of the output. Used for setting .so file name for libcronet
    self.stem = None

  def to_string(self, output):
    if self.comment:
      output.append('// %s' % self.comment)
    output.append('%s {' % self.type)
    self._output_field(output, 'name')
    self._output_field(output, 'srcs')
    self._output_field(output, 'shared_libs')
    self._output_field(output, 'static_libs')
    self._output_field(output, 'whole_static_libs')
    self._output_field(output, 'runtime_libs')
    self._output_field(output, 'tools')
    self._output_field(output, 'cmd', sort=False)
    if self.host_supported:
      self._output_field(output, 'host_supported')
    if not self.device_supported:
      self._output_field(output, 'device_supported')
    if self.vendor_available:
      self._output_field(output, 'vendor_available')
    self._output_field(output, 'init_rc')
    self._output_field(output, 'out')
    self._output_field(output, 'export_include_dirs')
    self._output_field(output, 'generated_headers')
    self._output_field(output, 'export_generated_headers')
    self._output_field(output, 'export_static_lib_headers')
    self._output_field(output, 'defaults')
    self._output_field(output, 'cflags')
    self._output_field(output, 'include_dirs')
    self._output_field(output, 'local_include_dirs')
    self._output_field(output, 'header_libs')
    self._output_field(output, 'required')
    self._output_field(output, 'dist')
    self._output_field(output, 'strip')
    self._output_field(output, 'tool_files')
    self._output_field(output, 'data')
    self._output_field(output, 'stl')
    self._output_field(output, 'cpp_std')
    self._output_field(output, 'apex_available')
    self._output_field(output, 'min_sdk_version')
    self._output_field(output, 'version_script')
    self._output_field(output, 'test_suites')
    self._output_field(output, 'test_config')
    self._output_field(output, 'stubs')
    self._output_field(output, 'proto')
    self._output_field(output, 'linker_scripts')
    self._output_field(output, 'cppflags')
    self._output_field(output, 'stem')
    if self.rtti:
      self._output_field(output, 'rtti')

    target_out = []
    for arch, target in sorted(self.target.items()):
      # _output_field calls getattr(self, arch).
      setattr(self, arch, target)
      self._output_field(target_out, arch)

    if target_out:
      output.append('    target: {')
      for line in target_out:
        output.append('    %s' % line)
      output.append('    },')

    output.append('}')
    output.append('')

  def add_android_static_lib(self, lib):
    if self.type == 'cc_binary_host':
      raise Exception('Adding Android static lib for host tool is unsupported')
    elif self.host_supported:
      self.target['android'].static_libs.add(lib)
    else:
      self.static_libs.add(lib)

  def add_android_shared_lib(self, lib):
    if self.type == 'cc_binary_host':
      raise Exception('Adding Android shared lib for host tool is unsupported')
    elif self.host_supported:
      self.target['android'].shared_libs.add(lib)
    else:
      self.shared_libs.add(lib)

  def _output_field(self, output, name, sort=True):
    value = getattr(self, name)
    return write_blueprint_key_value(output, name, value, sort)

  def is_compiled(self):
    return self.type not in ('cc_genrule', 'filegroup', 'cc_defaults')

  def is_genrule(self):
    return self.type == "cc_genrule"

  def has_input_files(self):
    for target in self.target.values():
      if len(target.srcs) > 0:
        return True
    return len(self.srcs) > 0 or any([len(target.srcs) > 0 for target in self.target.values()])

  def merge_attribute(self, key, source_module, allowed_archs, source_key = None):
    """
    Merges the value of the attribute `source_key` for the `dep_module` with
    the value of the attribute `key` for this module. If the value of the
    `source_key` is equal to None. Then `key` is used for both modules.

    This merges the attribute for both non-arch and archs
    specified in `allowed_archs`.
    :param key: The attribute used for merging in the calling module. Also
    used for `dep_module` if the `source_key` is None.
    :param source_module: The module where data is propagated from.
    :param allowed_archs: A list of archs to merge the attribute on.
    :param source_key: if the attribute merged from the `dep_module`
    is different from the `key`
    """
    if not source_key:
      source_key = key
    self.__dict__[key].update(source_module.__dict__[source_key])
    for arch_name in source_module.target.keys():
      if arch_name in allowed_archs:
        self.target[arch_name].__dict__[key].update(
            source_module.target[arch_name].__dict__[source_key])

class Blueprint(object):
  """In-memory representation of an Android.bp file."""

  def __init__(self):
    self.modules = {}

  def add_module(self, module):
    """Adds a new module to the blueprint, replacing any existing module
        with the same name.

        Args:
            module: Module instance.
        """
    self.modules[module.name] = module

  def to_string(self, output):
    for m in sorted(self.modules.values(), key=lambda m: m.name):
      m.to_string(output)


def label_to_module_name(label):
  """Turn a GN label (e.g., //:perfetto_tests) into a module name."""
  module = re.sub(r'^//:?', '', label)
  module = re.sub(r'[^a-zA-Z0-9_]', '_', module)

  if not module.startswith(module_prefix):
    return module_prefix + module
  return module


def is_supported_source_file(name):
  """Returns True if |name| can appear in a 'srcs' list."""
  return os.path.splitext(name)[1] in ['.c', '.cc', '.cpp', '.java', '.proto', '.S']


def create_proto_modules(blueprint, gn, target):
  """Generate genrules for a proto GN target.

    GN actions are used to dynamically generate files during the build. The
    Soong equivalent is a genrule. This function turns a specific kind of
    genrule which turns .proto files into source and header files into a pair
    equivalent genrules.

    Args:
        blueprint: Blueprint instance which is being generated.
        target: gn_utils.Target object.

    Returns:
        The source_genrule module.
    """
  assert (target.type == 'proto_library')

  protoc_gn_target_name = gn.get_target('//third_party/protobuf:protoc').name
  protoc_module_name = label_to_module_name(protoc_gn_target_name)
  tools = {protoc_module_name}
  cpp_out_dir = '$(genDir)/%s/%s/' % (tree_path, target.proto_in_dir)
  target_module_name = label_to_module_name(target.name)

  # In GN builds the proto path is always relative to the output directory
  # (out/tmp.xxx).
  cmd = ['$(location %s)' % protoc_module_name]
  cmd += ['--proto_path=%s/%s' % (tree_path, target.proto_in_dir)]

  if buildtools_protobuf_src in target.proto_paths:
    cmd += ['--proto_path=%s' % android_protobuf_src]

  # We don't generate any targets for source_set proto modules because
  # they will be inlined into other modules if required.
  if target.proto_plugin == 'source_set':
    return None

  # Descriptor targets only generate a single target.
  if target.proto_plugin == 'descriptor':
    out = '{}.bin'.format(target_module_name)

    cmd += ['--descriptor_set_out=$(out)']
    cmd += ['$(in)']

    descriptor_module = Module('cc_genrule', target_module_name, target.name)
    descriptor_module.cmd = ' '.join(cmd)
    descriptor_module.out = [out]
    descriptor_module.tools = tools
    blueprint.add_module(descriptor_module)

    # Recursively extract the .proto files of all the dependencies and
    # add them to srcs.
    descriptor_module.srcs.update(
        gn_utils.label_to_path(src) for src in target.sources)
    for dep in target.transitive_proto_deps:
      current_target = gn.get_target(dep)
      descriptor_module.srcs.update(
          gn_utils.label_to_path(src) for src in current_target.sources)

    return descriptor_module

  # We create two genrules for each proto target: one for the headers and
  # another for the sources. This is because the module that depends on the
  # generated files needs to declare two different types of dependencies --
  # source files in 'srcs' and headers in 'generated_headers' -- and it's not
  # valid to generate .h files from a source dependency and vice versa.
  source_module_name = target_module_name + '_gen'
  source_module = Module('cc_genrule', source_module_name, target.name)
  blueprint.add_module(source_module)
  source_module.srcs.update(
      gn_utils.label_to_path(src) for src in target.sources)

  header_module = Module('cc_genrule', source_module_name + '_headers',
                         target.name)
  blueprint.add_module(header_module)
  header_module.srcs = set(source_module.srcs)

  # TODO(primiano): at some point we should remove this. This was introduced
  # by aosp/1108421 when adding "protos/" to .proto include paths, in order to
  # avoid doing multi-repo changes and allow old clients in the android tree
  # to still do the old #include "perfetto/..." rather than
  # #include "protos/perfetto/...".
  header_module.export_include_dirs = {'.', 'protos'}
  # Since the .cc file and .h get created by a different gerule target, they
  # are not put in the same intermediate path, so local includes do not work
  # without explictily exporting the include dir.
  header_module.export_include_dirs.add(target.proto_in_dir)

  # This function does not return header_module so setting apex_available attribute here.
  header_module.apex_available.add(tethering_apex)

  source_module.genrule_srcs.add(':' + source_module.name)
  source_module.genrule_headers.add(header_module.name)

  if target.proto_plugin == 'proto':
    suffixes = ['pb']
    source_module.genrule_shared_libs.add('libprotobuf-cpp-lite')
    cmd += ['--cpp_out=lite=true:' + cpp_out_dir]
  elif target.proto_plugin == 'protozero':
    suffixes = ['pbzero']
    plugin = create_modules_from_target(blueprint, gn, protozero_plugin)
    tools.add(plugin.name)
    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
    cmd += ['--plugin_out=wrapper_namespace=pbzero:' + cpp_out_dir]
  elif target.proto_plugin == 'cppgen':
    suffixes = ['gen']
    plugin = create_modules_from_target(blueprint, gn, cppgen_plugin)
    tools.add(plugin.name)
    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
    cmd += ['--plugin_out=wrapper_namespace=gen:' + cpp_out_dir]
  elif target.proto_plugin == 'ipc':
    suffixes = ['ipc']
    plugin = create_modules_from_target(blueprint, gn, ipc_plugin)
    tools.add(plugin.name)
    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
    cmd += ['--plugin_out=wrapper_namespace=gen:' + cpp_out_dir]
  else:
    raise Error('Unsupported proto plugin: %s' % target.proto_plugin)

  cmd += ['$(in)']
  source_module.cmd = ' '.join(cmd)
  header_module.cmd = source_module.cmd
  source_module.tools = tools
  header_module.tools = tools

  for sfx in suffixes:
    source_module.out.update('%s/%s' %
                             (tree_path, src.replace('.proto', '.%s.cc' % sfx))
                             for src in source_module.srcs)
    header_module.out.update('%s/%s' %
                             (tree_path, src.replace('.proto', '.%s.h' % sfx))
                             for src in header_module.srcs)
  return source_module


def create_proto_group_modules(blueprint, gn, module_name, target_names):
  # TODO(lalitm): today, we're only adding a Java lite module because that's
  # the only one used in practice. In the future, if we need other target types
  # (e.g. C++, Java full etc.) add them here.
  bp_module_name = label_to_module_name(module_name) + '_java_protos'
  module = Module('java_library', bp_module_name, bp_module_name)
  module.comment = f'''GN: [{', '.join(target_names)}]'''
  module.proto = {'type': 'lite', 'canonical_path_from_root': False}

  for name in target_names:
    target = gn.get_target(name)
    module.srcs.update(gn_utils.label_to_path(src) for src in target.sources)
    for dep_label in target.transitive_proto_deps:
      dep = gn.get_target(dep_label)
      module.srcs.update(gn_utils.label_to_path(src) for src in dep.sources)

  blueprint.add_module(module)


class BaseActionSanitizer():
  def __init__(self, target):
    # Just to be on the safe side, create a deep-copy.
    self.target = copy.deepcopy(target)
    # Convert ['--param=value'] to ['--param', 'value'] for consistency.
    self.target.args = [str for it in self.target.args for str in it.split('=')]

  # There are three types of args:
  # - flags (--flag)
  # - value args (--arg value)
  # - list args (--arg value1 --arg value2)
  # Note that the set of list args contains the set of value args.
  # value args must have exactly one arg value pair but list args could have one arg value pair.
  # This is because list args with one arg value pair and value args can not be distinguished only
  # from the desc.json
  # Some functions provide special implementations for each type, while others
  # work on all of them.
  def _has_arg(self, arg):
    return arg in self.target.args

  def _get_arg_indices(self, target_arg):
    return [i for i, arg in enumerate(self.target.args) if arg == target_arg]

  # Whether an arg value pair appears once or more times
  def _is_list_arg(self, arg):
    indices = self._get_arg_indices(arg)
    return len(indices) > 0 and all([not self.target.args[i + 1].startswith('--') for i in indices])

  def _update_list_arg(self, arg, func, throw_if_absent = True):
    if self._should_fail_silently(arg, throw_if_absent):
      return
    assert(self._is_list_arg(arg))
    indices = self._get_arg_indices(arg)
    for i in indices:
      self._set_arg_at(i + 1, func(self.target.args[i + 1]))

  # Whether an arg value pair appears exactly once
  def _is_value_arg(self, arg):
    if operator.countOf(self.target.args, arg) != 1:
      return False
    i = self.target.args.index(arg)
    return not self.target.args[i + 1].startswith('--')

  def _get_value_arg(self, arg):
    assert(self._is_value_arg(arg))
    i = self.target.args.index(arg)
    return self.target.args[i + 1]

  # used to check whether a function call should cause an error when an arg is
  # missing.
  def _should_fail_silently(self, arg, throw_if_absent):
    return not throw_if_absent and not self._has_arg(arg)

  def _set_value_arg(self, arg, value, throw_if_absent = True):
    if self._should_fail_silently(arg, throw_if_absent):
      return
    assert(self._is_value_arg(arg))
    i = self.target.args.index(arg)
    self.target.args[i + 1] = value

  def _update_value_arg(self, arg, func, throw_if_absent = True):
    if self._should_fail_silently(arg, throw_if_absent):
      return
    self._set_value_arg(arg, func(self._get_value_arg(arg)))

  def _set_arg_at(self, position, value):
    self.target.args[position] = value

  def _delete_value_arg(self, arg, throw_if_absent = True):
    if self._should_fail_silently(arg, throw_if_absent):
      return
    assert(self._is_value_arg(arg))
    i = self.target.args.index(arg)
    self.target.args.pop(i)
    self.target.args.pop(i)

  def _append_arg(self, arg, value):
    self.target.args.append(arg)
    self.target.args.append(value)

  # wrap filename in location tag.
  def _add_location_tag(self, filename):
    return '$(location %s)' % filename

  # applies common directory transformation that *should* be universally applicable.
  # TODO: verify if it actually *is* universally applicable.
  def _sanitize_filepath(self, filepath):
    # Careful, order matters!
    # delete all leading ../
    filepath = re.sub('^(\.\./)+', '', filepath)
    filepath = re.sub('^gen/jni_headers', '$(genDir)', filepath)
    filepath = re.sub('^gen', '$(genDir)', filepath)
    return filepath

  # Iterate through all the args and apply function
  def _update_all_args(self, func):
    self.target.args = [func(arg) for arg in self.target.args]

  def get_args(self):
    return self.target.args

class WriteBuildDateHeaderSanitizer(BaseActionSanitizer):
  def get_args(self):
    self._set_arg_at(0, '$(out)')
    return super().get_args()

class WriteBuildFlagHeaderSanitizer(BaseActionSanitizer):
  def get_args(self):
    self._set_value_arg('--gen-dir', '.')
    self._set_value_arg('--output', '$(out)')
    return super().get_args()

class JniGeneratorSanitizer(BaseActionSanitizer):
  def _add_location_tag_to_filepath(self, arg):
    if not arg.endswith('.class'):
      # --input_file supports both .class specifiers or source files as arguments.
      # Only source files need to be wrapped inside a $(location <label>) tag.
      arg = self._add_location_tag(arg)
    return arg

  def get_args(self):
    self._update_value_arg('--jar_file', self._sanitize_filepath, False)
    self._update_value_arg('--jar_file', self._add_location_tag, False)
    if self._has_arg('--jar_file'):
      self._append_arg('--javap', '$$(find out/.path -name javap)')
    self._update_value_arg('--output_dir', self._sanitize_filepath)
    self._update_value_arg('--includes', self._sanitize_filepath, False)
    self._delete_value_arg('--prev_output_dir', False)
    self._update_list_arg('--input_file', self._sanitize_filepath)
    self._update_list_arg('--input_file', self._add_location_tag_to_filepath)
    return super().get_args()

class JniRegistrationGeneratorSanitizer(BaseActionSanitizer):
  def get_args(self):
    self._update_value_arg('--depfile', self._sanitize_filepath)
    self._update_value_arg('--srcjar-path', self._sanitize_filepath)
    self._update_value_arg('--header-path', self._sanitize_filepath)
    self._set_value_arg('--sources-files', '$(genDir)/java.sources')
    # update_jni_registration_module removes them from the srcs of the module
    # It might be better to remove sources by '--sources-exclusions'
    self._delete_value_arg('--sources-exclusions')
    return super().get_args()

class VersionSanitizer(BaseActionSanitizer):
  def _sanitize_version_filepath(self, arg):
    if arg.startswith('../../'):
      arg = self._sanitize_filepath(arg)
      arg = self._add_location_tag(arg)
    return arg

  def _sanitize_eval(self):
    assert (self._is_value_arg('-e'))
    # arg for -e EVAL option should be passed in -e PATCH_HI=int(PATCH)//256 format.
    index = self.target.args.index('-e')
    value = '%s=\'%s\'' % (self.target.args[index + 1], self.target.args[index + 2])
    self._set_arg_at(index + 1, value)
    self.target.args.pop(index + 2)

  def get_args(self):
    self._set_value_arg('-o', '$(out)')
    # args for the version.py contain file path without leading --arg key. So apply sanitize
    # function for all the args.
    self._update_all_args(self._sanitize_version_filepath)
    self._sanitize_eval()
    return super().get_args()

def get_action_sanitizer(target):
  if target.script == "//build/write_buildflag_header.py":
    return WriteBuildFlagHeaderSanitizer(target)
  elif target.script == "//build/write_build_date_header.py":
    return WriteBuildDateHeaderSanitizer(target)
  elif target.script == '//base/android/jni_generator/jni_generator.py':
    return JniGeneratorSanitizer(target)
  elif target.script == '//base/android/jni_generator/jni_registration_generator.py':
    return JniRegistrationGeneratorSanitizer(target)
  elif target.script == "//build/util/version.py":
    return VersionSanitizer(target)
  else:
    # TODO: throw exception here once all script hacks have been converted.
    return BaseActionSanitizer(target)

def create_action_foreach_modules(blueprint, target):
  """ The following assumes that rebase_path exists in the args.
  The args of an action_foreach contains hints about which output files are generated
  by which source files.
  This is copied directly from the args
  "gen/net/base/registry_controlled_domains/{{source_name_part}}-reversed-inc.cc"
  So each source file will generate an output whose name is the {source_name-reversed-inc.cc}
  """
  new_args = []
  for i, src in enumerate(sorted(target.sources)):
    # don't add script arg for the first source -- create_action_module
    # already does this.
    if i != 0:
      new_args.append('&& python3 $(location %s)' %
                   gn_utils.label_to_path(target.script))
    for arg in target.args:
      if '{{source}}' in arg:
        new_args.append('$(location %s)' % (gn_utils.label_to_path(src)))
      elif '{{source_name_part}}' in arg:
        source_name_part = src.split("/")[-1] # Get the file name only
        source_name_part = source_name_part.split(".")[0] # Remove the extension (Ex: .cc)
        file_name = arg.replace('{{source_name_part}}', source_name_part).split("/")[-1]
        # file_name represent the output file name. But we need the whole path
        # This can be found from target.outputs.
        for out in target.outputs:
          if out.endswith(file_name):
            new_args.append('$(location %s)' % out)
      else:
        new_args.append(arg)

  target.args = new_args
  return create_action_module(blueprint, target)

def create_action_module(blueprint, target):
  bp_module_name = label_to_module_name(target.name)
  module = Module('cc_genrule', bp_module_name, target.name)

  sanitizer = get_action_sanitizer(target)
  target.args = sanitizer.get_args()

  if target.script == '//base/android/jni_generator/jni_generator.py':
    # fix target.output directory to match #include statements.
    target.outputs = [re.sub('^jni_headers/', '', out) for out in target.outputs]

  elif target.script == '//base/android/jni_generator/jni_registration_generator.py':
    # jni_registration_generator.py pulls in some config dependencies that we
    # do not handle. Remove them.
    # TODO: find a better way to do this.
    target.deps.clear()

    target.inputs = [file for file in target.inputs if not file.startswith('//out/')]
  elif target.script == "//net/tools/dafsa/make_dafsa.py":
    # This script generates .cc files but source (registry_controlled_domain.cc) in the target that
    # depends on this target includes .cc file this script generates.
    module.genrule_headers.add(module.name)
  elif target.script == "//build/util/version.py":
    # android_chrome_version.py is not specified in anywhere but version.py imports this file
    module.tool_files.add('build/util/android_chrome_version.py')

  script = gn_utils.label_to_path(target.script)
  module.tool_files.add(script)

  # Handle passing parameters via response file by piping them into the script
  # and reading them from /dev/stdin.
  response_file = '{{response_file_name}}'
  use_response_file = response_file in target.args
  if use_response_file:
    # Replace {{response_file_contents}} with /dev/stdin
    target.args = ['/dev/stdin' if it == response_file else it for it in target.args]

  # escape " and \$ in target.args.
  # once all actions are properly implemented, this may not be necessary anymore.
  # TODO: is this the right place to do this?
  target.args = [arg.replace('"', r'\"') for arg in target.args]
  target.args = [arg.replace(r'\$', r'\\$') for arg in target.args]

  # put all args on a new line for better diffs.
  NEWLINE = ' " +\n         "'
  arg_string = NEWLINE.join(target.args)
  module.cmd = '$(location %s) %s' % (script, arg_string)

  if use_response_file:
    # Pipe response file contents into script
    module.cmd = 'echo \'%s\' |%s%s' % (target.response_file_contents, NEWLINE, module.cmd)

  if any(os.path.splitext(it)[1] == '.h' for it in target.outputs):
    module.genrule_headers.add(bp_module_name)

  # gn treats inputs and sources for actions equally.
  # soong only supports source files inside srcs, non-source files are added as
  # tool_files dependency.
  for it in target.sources or target.inputs:
    if is_supported_source_file(it):
      module.srcs.add(gn_utils.label_to_path(it))
    else:
      module.tool_files.add(gn_utils.label_to_path(it))

  # Actions using template "action_with_pydeps" also put script inside inputs.
  # TODO: it might make sense to filter inputs inside GnParser.
  if script in module.srcs:
    module.srcs.remove(script)

  module.out.update(target.outputs)

  if target.script == "//base/android/jni_generator/jni_generator.py":
    # android_jar.classes should be part of the tools as it list implicit classes
    # for the script to generate JNI headers.
    module.tool_files.add("base/android/jni_generator/android_jar.classes")
  elif target.script == '//base/android/jni_generator/jni_registration_generator.py':
    # jni_registration_generator.py doesn't work with python2
    module.cmd = "python3 " + module.cmd
    # Path in the original sources file does not work in genrule.
    # So creating sources file in cmd based on the srcs of this target.
    # Adding ../$(current_dir)/ to the head because jni_registration_generator.py uses the files
    # whose path startswith(..)
    commands = ["current_dir=`basename \\\`pwd\\\``;",
                "for f in $(in);",
                "do",
                "echo \\\"../$$current_dir/$$f\\\" >> $(genDir)/java.sources;",
                "done;",
                module.cmd]

    # .h file jni_registration_generator.py generates has #define with directory name.
    # With the genrule env that contains "." which is invalid. So replace that at the end of cmd.
    commands.append(";sed -i -e 's/OUT_SOONG_.TEMP_SBOX_.*_OUT/GEN/g' ")
    commands.append("$(genDir)/components/cronet/android/cronet_jni_registration.h")
    module.cmd = NEWLINE.join(commands)

  blueprint.add_module(module)
  return module



def _get_cflags(cflags, defines):
  cflags = {flag for flag in cflags if flag in cflag_allowlist}
  # Consider proper allowlist or denylist if needed
  cflags |= set("-D%s" % define.replace("\"", "\\\"") for define in defines)
  return cflags

def set_module_flags(module, cflags, defines):
  module.cflags.update(_get_cflags(cflags, defines))
  # TODO: implement proper cflag parsing.
  for flag in cflags:
    if '-std=' in flag:
      module.cpp_std = flag[len('-std='):]
    if '-fexceptions' in flag:
      module.cppflags.add('-fexceptions')

def add_genrule_per_arch(module, dep_module, type):
  module.generated_headers.update(dep_module.genrule_headers)
  # If the module is a static library, export all the generated headers.
  if type == 'cc_library_static':
    module.export_generated_headers.update(dep_module.genrule_headers)
  module.srcs.update(dep_module.genrule_srcs)
  module.shared_libs.update(dep_module.genrule_shared_libs)
  module.header_libs.update(dep_module.genrule_header_libs)

def set_module_include_dirs(module, cflags, include_dirs):
  for flag in cflags:
    if '-isystem' in flag:
      module.local_include_dirs.add(flag[len('-isystem../../'):])

  # Adding local_include_dirs is necessary due to source_sets / filegroups
  # which do not properly propagate include directories.
  # Filter any directory inside //out as a) this directory does not exist for
  # aosp / soong builds and b) the include directory should already be
  # configured via library dependency.
  module.local_include_dirs.update([gn_utils.label_to_path(d)
                                 for d in include_dirs
                                 if not re.match('^//out/.*', d)])


def create_modules_from_target(blueprint, gn, gn_target_name):
  """Generate module(s) for a given GN target.

    Given a GN target name, generate one or more corresponding modules into a
    blueprint. The only case when this generates >1 module is proto libraries.

    Args:
        blueprint: Blueprint instance which is being generated.
        gn: gn_utils.GnParser object.
        gn_target_name: GN target for module generation.
    """
  bp_module_name = label_to_module_name(gn_target_name)
  if bp_module_name in blueprint.modules:
    return blueprint.modules[bp_module_name]
  target = gn.get_target(gn_target_name)
  log.info('create modules for %s (%s)', target.name, target.type)

  if target.type == 'executable':
    if target.testonly:
      module_type = 'cc_test'
    else:
      # Can be used for both host and device targets.
      module_type = 'cc_binary'
    module = Module(module_type, bp_module_name, gn_target_name)
  elif target.type == 'static_library':
    module = Module('cc_library_static', bp_module_name, gn_target_name)
  elif target.type == 'shared_library':
    module = Module('cc_library_shared', bp_module_name, gn_target_name)
  elif target.type == 'source_set':
    module = Module('cc_object', bp_module_name, gn_target_name)
  elif target.type == 'group':
    # "group" targets are resolved recursively by gn_utils.get_target().
    # There's nothing we need to do at this level for them.
    return None
  elif target.type == 'proto_library':
    module = create_proto_modules(blueprint, gn, target)
    if module is None:
      return None
  elif target.type == 'action':
    module = create_action_module(blueprint, target)
  elif target.type == 'action_foreach':
    module = create_action_foreach_modules(blueprint, target)
  elif target.type == 'copy':
    # TODO: careful now! copy targets are not supported yet, but this will stop
    # traversing the dependency tree. For //base:base, this is not a big
    # problem as libicu contains the only copy target which happens to be a
    # leaf node.
    return None
  elif target.type == 'java_group':
    # Java targets are handled outside of create_modules_from_target.
    return None
  else:
    raise Error('Unknown target %s (%s)' % (target.name, target.type))

  blueprint.add_module(module)
  module.init_rc = target_initrc.get(target.name, [])
  module.srcs.update(
      gn_utils.label_to_path(src)
      for src in target.sources
      if is_supported_source_file(src) and not src.startswith("//out/test"))

  # Add arch-specific properties
  for arch_name, arch in target.arch.items():
    module.target[arch_name].srcs.update(
      gn_utils.label_to_path(src)
      for src in arch.sources
      if is_supported_source_file(src) and not src.startswith("//out/test"))

  module.rtti = target.rtti

  if target.type in gn_utils.LINKER_UNIT_TYPES:
    set_module_flags(module, target.cflags, target.defines)
    set_module_include_dirs(module, target.cflags, target.include_dirs)
    # TODO: set_module_xxx is confusing, apply similar function to module and target in better way.
    for arch_name, arch in target.arch.items():
      set_module_flags(module.target[arch_name], arch.cflags, arch.defines)
      # -Xclang -target-feature -Xclang +mte are used to enable MTE (Memory Tagging Extensions).
      # Flags which does not start with '-' could not be in the cflags so enabling MTE by
      # -march and -mcpu Feature Modifiers. MTE is only available on arm64. This is needed for
      # building //base/allocator/partition_allocator:partition_alloc for arm64.
      if '+mte' in arch.cflags and arch_name == 'android_arm64':
        module.target[arch_name].cflags.add('-march=armv8-a+memtag')
      set_module_include_dirs(module.target[arch_name], arch.cflags, arch.include_dirs)

  module.host_supported = target.host_supported()
  module.device_supported = target.device_supported()

  if module.is_genrule():
    module.apex_available.add(tethering_apex)

  if module.is_compiled():
    # Don't try to inject library/source dependencies into genrules or
    # filegroups because they are not compiled in the traditional sense.
    module.defaults = [defaults_module]
    for lib in target.libs:
      # Generally library names should be mangled as 'libXXX', unless they
      # are HAL libraries (e.g., android.hardware.health@2.0) or AIDL c++ / NDK
      # libraries (e.g. "android.hardware.power.stats-V1-cpp")
      android_lib = lib if '@' in lib or "-cpp" in lib or "-ndk" in lib \
        else 'lib' + lib
      if lib in shared_library_allowlist:
        module.add_android_shared_lib(android_lib)
      if lib in static_library_allowlist:
        module.add_android_static_lib(android_lib)

    # Remove prohibited include directories
    module.local_include_dirs = [d for d in module.local_include_dirs
                                 if d not in local_include_dirs_denylist]

  # If the module is a static library, export all the generated headers.
  if module.type == 'cc_library_static':
    module.export_generated_headers = module.generated_headers

  if module.name == 'cronet_aml_components_cronet_android_cronet':
    if target.output_name is None:
      raise Error('Failed to get output_name for libcronet name')
    # .so file name needs to match with CronetLibraryLoader.java (e.g. libcronet.109.0.5386.0.so)
    # So setting the output name based on the output_name from the desc.json
    module.stem = 'lib' + target.output_name

  # dep_name is an unmangled GN target name (e.g. //foo:bar(toolchain)).
  # Currently, only one module is generated from target even target has multiple toolchains.
  # And module is generated based on the first visited target.
  # Sort deps before iteration to make result deterministic.
  all_deps = sorted(target.deps | target.source_set_deps | target.transitive_proto_deps)
  for dep_name in all_deps:
    # |builtin_deps| override GN deps with Android-specific ones. See the
    # config in the top of this file.
    if dep_name in builtin_deps:
      builtin_deps[dep_name](module)
      continue

    dep_module = create_modules_from_target(blueprint, gn, dep_name)

    if dep_module is None:
      continue
    # TODO: Proper dependency check for genrule.
    # Currently, only propagating genrule dependencies.
    # Also, currently, all the dependencies are propagated upwards.
    # in gn, public_deps should be propagated but deps should not.
    # Not sure this information is available in the desc.json.
    # Following rule works for adding android_runtime_jni_headers to base:base.
    # If this doesn't work for other target, hardcoding for specific target
    # might be better.
    if module.is_genrule() and dep_module.is_genrule():
      module.genrule_headers.add(dep_module.name)
      module.genrule_headers.update(dep_module.genrule_headers)

    # For filegroups, and genrule, recurse but don't apply the
    # deps.
    if not module.is_compiled() or module.is_genrule():
      continue

    if dep_module.type == 'cc_library_shared':
      module.shared_libs.add(dep_module.name)
    elif dep_module.type == 'cc_library_static':
      module.static_libs.add(dep_module.name)
    elif dep_module.type == 'cc_object':
      module.merge_attribute('generated_headers', dep_module, target.arch.keys())
      if module.type != 'cc_object':
        if dep_module.has_input_files():
          # Only add it as part of srcs if the dep_module has input files otherwise
          # this would throw an error.
          module.srcs.add(":" + dep_module.name)
        module.merge_attribute('export_generated_headers', dep_module,
                         target.arch.keys(), 'generated_headers')
    elif dep_module.type == 'cc_genrule':
      module.merge_attribute('generated_headers', dep_module, [], 'genrule_headers')
      module.merge_attribute('srcs', dep_module, [], 'genrule_srcs')
      module.merge_attribute('shared_libs', dep_module, [], 'genrule_shared_libs')
      module.merge_attribute('header_libs', dep_module, [], 'genrule_header_libs')
      if module.type not in ["cc_object"]:
        module.merge_attribute('export_generated_headers', dep_module, [],
                         'genrule_headers')
    elif dep_module.type == 'cc_binary':
      continue  # Ignore executables deps (used by cmdline integration tests).
    else:
      raise Error('Unknown dep %s (%s) for target %s' %
                  (dep_module.name, dep_module.type, module.name))

  for arch_name, arch in target.arch.items():
    for dep_name in arch.deps:
      dep_module = create_modules_from_target(blueprint, gn, dep_name)
      # Arch-specific dependencies currently only include cc_library_static.
      # Revisit this approach once we need to support more target types.
      if dep_module.type == 'cc_library_static':
        module.target[arch_name].static_libs.add(dep_module.name)
      elif dep_module.type == 'cc_genrule':
        if dep_module.name.endswith(arch_name):
          module.target[arch_name].generated_headers.update(dep_module.genrule_headers)
          module.target[arch_name].srcs.update(dep_module.genrule_srcs)
          module.target[arch_name].shared_libs.update(dep_module.genrule_shared_libs)
          module.target[arch_name].header_libs.update(dep_module.genrule_header_libs)
          if module.type not in ["cc_object"]:
            module.target[arch_name].export_generated_headers.update(
              dep_module.genrule_headers)
      else:
        raise Error('Unsupported arch-specific dependency %s of target %s with type %s' %
                    (dep_module.name, target.name, dep_module.type))
    for dep_name in arch.source_set_deps:
      dep_module = create_modules_from_target(blueprint, gn, dep_name)
      if dep_module.type == 'cc_object':
        if module.type != 'cc_object':
          # We only want to bubble up cc_objects for modules that are not cc_objects
          # otherwise they'd be recompiled and that would cause multiple symbol redefinitions.
          if dep_module.has_input_files():
            # Only add it as part of srcs if the dep_module has input files otherwise
            # this would throw an error.
            module.target[arch_name].srcs.add(":" + dep_module.name)
      else:
        raise Error('Unsupported arch-specific dependency %s of target %s with type %s' %
                    (dep_module.name, target.name, dep_module.type))
  return module

def create_java_module(blueprint, gn):
  bp_module_name = module_prefix + 'java'
  module = Module('java_library', bp_module_name, '//gn:java')
  module.srcs.update([gn_utils.label_to_path(source) for source in gn.java_sources])
  blueprint.add_module(module)

def update_jni_registration_module(module, gn):
  # TODO: deny list is in the arg of jni_registration_generator.py. Should not be hardcoded
  deny_list = [
    '//base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java',
    '//base/android/java/src/org/chromium/base/library_loader/LibraryPrefetcher.java',
    '//base/android/java/src/org/chromium/base/process_launcher/ChildProcessService.java',
    '//base/android/java/src/org/chromium/base/SysUtils.java']

  # TODO: java_sources might not contain all the required java files
  module.srcs.update([gn_utils.label_to_path(source)
                      for source in gn.java_sources if source not in deny_list])

def create_blueprint_for_targets(gn, targets):
  """Generate a blueprint for a list of GN targets."""
  blueprint = Blueprint()

  # Default settings used by all modules.
  defaults = Module('cc_defaults', defaults_module, '//gn:default_deps')
  defaults.cflags = [
      '-DGOOGLE_PROTOBUF_NO_RTTI',
      '-Wno-error=return-type',
      '-Wno-non-virtual-dtor',
      '-Wno-macro-redefined',
      '-Wno-missing-field-initializers',
      '-Wno-sign-compare',
      '-Wno-sign-promo',
      '-Wno-unused-parameter',
      '-Wno-null-pointer-subtraction', # Needed to libevent
      '-Wno-deprecated-non-prototype', # needed for zlib
      '-fvisibility=hidden',
      '-Wno-ambiguous-reversed-operator', # needed for icui18n
      '-Wno-unreachable-code-loop-increment', # needed for icui18n
      '-O2',
      '-fPIC',
  ]
  # Chromium builds do not add a dependency for headers found inside the
  # sysroot, so they are added globally via defaults.
  defaults.target['android'].header_libs = [
      'media_ndk_headers',
      'jni_headers',
  ]
  defaults.target['host'].cflags = [
      # -DANDROID is added by default but target.defines contain -DANDROID if
      # it's required.  So adding -UANDROID to cancel default -DANDROID if it's
      # not specified.
      # Note: -DANDROID is not consistently applied across the chromium code
      # base, so it is removed unconditionally for host targets.
      '-UANDROID',
  ]
  defaults.stl = 'none'
  defaults.min_sdk_version = 29
  defaults.apex_available.add(tethering_apex)
  blueprint.add_module(defaults)

  for target in targets:
    create_modules_from_target(blueprint, gn, target)

  create_java_module(blueprint, gn)
  for module in blueprint.modules.values():
    if 'cronet_jni_registration' in module.name:
      update_jni_registration_module(module, gn)

  # Merge in additional hardcoded arguments.
  for module in blueprint.modules.values():
    for key, add_val in additional_args.get(module.name, []):
      curr = getattr(module, key)
      if add_val and isinstance(add_val, set) and isinstance(curr, set):
        curr.update(add_val)
      elif isinstance(add_val, str) and (not curr or isinstance(curr, str)):
        setattr(module, key, add_val)
      elif isinstance(add_val, bool) and (not curr or isinstance(curr, bool)):
        setattr(module, key, add_val)
      elif isinstance(add_val, dict) and isinstance(curr, dict):
        curr.update(add_val)
      elif isinstance(add_val, dict) and isinstance(curr, Target):
        curr.__dict__.update(add_val)
      else:
        raise Error('Unimplemented type %r of additional_args: %r' %
                    (type(add_val), key))

  return blueprint


def main():
  parser = argparse.ArgumentParser(
      description='Generate Android.bp from a GN description.')
  parser.add_argument(
      '--desc',
      help='GN description (e.g., gn desc out --format=json --all-toolchains "//*".' +
           'You can specify multiple --desc options for different target_cpu',
      required=True,
      action='append'
  )
  parser.add_argument(
      '--extras',
      help='Extra targets to include at the end of the Blueprint file',
      default=os.path.join(gn_utils.repo_root(), 'Android.bp.extras'),
  )
  parser.add_argument(
      '--output',
      help='Blueprint file to create',
      default=os.path.join(gn_utils.repo_root(), 'Android.bp'),
  )
  parser.add_argument(
      '-v',
      '--verbose',
      help='Print debug logs.',
      action='store_true',
  )
  parser.add_argument(
      'targets',
      nargs=argparse.REMAINDER,
      help='Targets to include in the blueprint (e.g., "//:perfetto_tests")'
  )
  args = parser.parse_args()

  if args.verbose:
    log.basicConfig(format='%(levelname)s:%(funcName)s:%(message)s', level=log.DEBUG)

  targets = args.targets or default_targets
  gn = gn_utils.GnParser()
  for desc_file in args.desc:
    with open(desc_file) as f:
      desc = json.load(f)
    for target in targets:
      gn.parse_gn_desc(desc, target)
  blueprint = create_blueprint_for_targets(gn, targets)
  project_root = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
  tool_name = os.path.relpath(os.path.abspath(__file__), project_root)

  # Add any proto groups to the blueprint.
  for l_name, t_names in proto_groups.items():
    create_proto_group_modules(blueprint, gn, l_name, t_names)

  output = [
      """// Copyright (C) 2022 The Android Open Source Project
//
// 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.
//
// This file is automatically generated by %s. Do not edit.
""" % (tool_name)
  ]
  blueprint.to_string(output)
  if os.path.exists(args.extras):
    with open(args.extras, 'r') as r:
      for line in r:
        output.append(line.rstrip("\n\r"))

  out_files = []

  # Generate the Android.bp file.
  out_files.append(args.output + '.swp')
  with open(out_files[-1], 'w') as f:
    f.write('\n'.join(output))
    # Text files should have a trailing EOL.
    f.write('\n')

  return 0


if __name__ == '__main__':
  sys.exit(main())