licenses.py

#!/usr/bin/env python
# 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.

"""Utility for checking and processing licensing information in third_party
directories.

Usage: licenses.py <command>

Commands:
  scan     scan third_party directories, verifying that we have licensing info
  credits  generate about:credits on stdout

(You can also import this as a module.)
"""
from __future__ import print_function

import argparse
import codecs
import json
import os
import shutil
import re
import subprocess
import sys
import tempfile

if sys.version_info.major == 2:
  import cgi as html
else:
  import html

# TODO(agrieve): Move build_utils.WriteDepFile into a non-android directory.
_REPOSITORY_ROOT = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
sys.path.insert(0, os.path.join(_REPOSITORY_ROOT, 'build/android/gyp'))
from util import build_utils


# Paths from the root of the tree to directories to skip.
PRUNE_PATHS = set([
    # Placeholder directory only, not third-party code.
    os.path.join('third_party','adobe'),

    # Will remove it once converted private sdk using cipd.
    os.path.join('third_party','android_tools_internal'),

    # Build files only, not third-party code.
    os.path.join('third_party','widevine'),

    # Only binaries, used during development.
    os.path.join('third_party','valgrind'),

    # Used for development and test, not in the shipping product.
    os.path.join('build','secondary'),
    os.path.join('third_party','bison'),
    os.path.join('third_party','blanketjs'),
    os.path.join('third_party','chromite'),
    os.path.join('third_party','cygwin'),
    os.path.join('third_party','gles2_conform'),
    os.path.join('third_party','gnu_binutils'),
    os.path.join('third_party','gold'),
    os.path.join('third_party','gperf'),
    os.path.join('third_party','lighttpd'),
    os.path.join('third_party','llvm'),
    os.path.join('third_party','llvm-build'),
    os.path.join('third_party','mingw-w64'),
    os.path.join('third_party','nacl_sdk_binaries'),
    os.path.join('third_party','pefile'),
    os.path.join('third_party','perl'),
    os.path.join('third_party','psyco_win32'),
    os.path.join('third_party','pyelftools'),
    os.path.join('third_party','pylib'),
    os.path.join('third_party','pywebsocket'),
    os.path.join('third_party','syzygy'),

    # Chromium code.
    os.path.join('tools', 'swarming_client'),

    # Stuff pulled in from chrome-internal for official builds/tools.
    os.path.join('third_party', 'clear_cache'),
    os.path.join('third_party', 'gnu'),
    os.path.join('third_party', 'googlemac'),
    os.path.join('third_party', 'pcre'),
    os.path.join('third_party', 'psutils'),
    os.path.join('third_party', 'sawbuck'),
    # See crbug.com/350472
    os.path.join('chrome', 'browser', 'resources', 'chromeos', 'quickoffice'),
    # Chrome for Android proprietary code.
    os.path.join('clank'),

    # Redistribution does not require attribution in documentation.
    os.path.join('third_party','directxsdk'),

    # For testing only, presents on some bots.
    os.path.join('isolate_deps_dir'),

    # Mock test data.
    os.path.join('tools', 'binary_size', 'libsupersize', 'testdata'),

    # Overrides some WebRTC files, same license. Skip this one.
    os.path.join('third_party', 'webrtc_overrides'),
])

# Directories we don't scan through.
VCS_METADATA_DIRS = ('.svn', '.git')
PRUNE_DIRS = VCS_METADATA_DIRS + ('layout_tests', )  # lots of subdirs

# A third_party directory can define this file, containing a list of
# subdirectories to process in addition to itself. Intended for directories
# that contain multiple others as transitive dependencies.
ADDITIONAL_PATHS_FILENAME = 'additional_readme_paths.json'

# A list of paths that contain license information but that would otherwise
# not be included.  Possible reasons include:
#   - Third party directories in //clank which are considered to be Google-owned
#   - Directories that are directly checked out from upstream, and thus
#     don't have a README.chromium
#   - Directories that contain example code, or build tooling.
#   - Nested third_party code inside other third_party libraries.
ADDITIONAL_PATHS = (
    os.path.join('chrome', 'common', 'extensions', 'docs', 'examples'),
    os.path.join('chrome', 'test', 'chromeos', 'autotest'),
    os.path.join('chrome', 'test', 'data'),
    os.path.join('native_client'),
    os.path.join('testing', 'gmock'),
    os.path.join('testing', 'gtest'),
    os.path.join('third_party', 'boringssl', 'src', 'third_party', 'fiat'),
    os.path.join('tools', 'gyp'),
    os.path.join('tools', 'page_cycler', 'acid3'),
    os.path.join('url', 'third_party', 'mozilla'),
    os.path.join('v8'),
    # Fake directories to include the strongtalk and fdlibm licenses.
    os.path.join('v8', 'strongtalk'),
    os.path.join('v8', 'fdlibm'),
)


# Directories where we check out directly from upstream, and therefore
# can't provide a README.chromium.  Please prefer a README.chromium
# wherever possible.
SPECIAL_CASES = {
    os.path.join('native_client'): {
        "Name": "native client",
        "URL": "http://code.google.com/p/nativeclient",
        "License": "BSD",
    },
    os.path.join('testing', 'gmock'): {
        "Name": "gmock",
        "URL": "http://code.google.com/p/googlemock",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('testing', 'gtest'): {
        "Name": "gtest",
        "URL": "http://code.google.com/p/googletest",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'angle'): {
        "Name": "Almost Native Graphics Layer Engine",
        "URL": "http://code.google.com/p/angleproject/",
        "License": "BSD",
    },
    os.path.join('third_party', 'cros_system_api'): {
        "Name": "Chromium OS system API",
        "URL": "http://www.chromium.org/chromium-os",
        "License": "BSD",
        # Absolute path here is resolved as relative to the source root.
        "License File": "/LICENSE.chromium_os",
    },
    os.path.join('third_party', 'devtools-frontend'): {
        # TODO(crbug.com/1151057): Remove this special case when issue is fixed.
        "Name": "Devtools-Frontend",
        "URL": "https://chromium.googlesource.com/devtools/devtools-frontend",
        "License": "BSD",
        "License File": "src/LICENSE",
    },
    os.path.join('third_party', 'lss'): {
        "Name": "linux-syscall-support",
        "URL": "http://code.google.com/p/linux-syscall-support/",
        "License": "BSD",
        "License File": "/LICENSE",
    },
    os.path.join('third_party', 'openscreen', 'src', 'third_party', 'abseil'): {
        "Name": "abseil",
        "URL": "https://github.com/abseil/abseil-cpp/",
        "License": "Apache 2.0",
        "License File": "/third_party/abseil-cpp/LICENSE",
    },
    os.path.join('third_party', 'openscreen', 'src', 'third_party',
                 'boringssl'):
    {
        "Name": "BoringSSL",
        "URL": "https://boringssl.googlesource.com/boringssl/",
        "License": "BSDish",
        "License File": "/third_party/boringssl/src/LICENSE",
    },
    os.path.join('third_party', 'openscreen', 'src', 'third_party', 'jsoncpp'):
    {
        "Name": "jsoncpp",
        "URL": "https://github.com/open-source-parsers/jsoncpp",
        "License": "MIT",
        "License File": "/third_party/jsoncpp/LICENSE",
    },
    os.path.join('third_party', 'openscreen', 'src', 'third_party', 'mozilla'):
    {
        "Name": "mozilla",
        "URL": "https://github.com/mozilla",
        "License": "MPL 1.1/GPL 2.0/LGPL 2.1",
        "License File": "LICENSE.txt",
    },
    os.path.join('third_party', 'pdfium'): {
        "Name": "PDFium",
        "URL": "http://code.google.com/p/pdfium/",
        "License": "BSD",
    },
    os.path.join('third_party', 'ppapi'): {
        "Name": "ppapi",
        "URL": "http://code.google.com/p/ppapi/",
    },
    os.path.join('third_party', 'scons-2.0.1'): {
        "Name": "scons-2.0.1",
        "URL": "http://www.scons.org",
        "License": "MIT",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'catapult'): {
        "Name": "catapult",
        "URL": "https://github.com/catapult-project/catapult",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'crashpad', 'crashpad', 'third_party', 'lss'): {
        "Name": "linux-syscall-support",
        "URL": "https://chromium.googlesource.com/linux-syscall-support/",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'crashpad', 'crashpad', 'third_party',
                 'mini_chromium'):
    {
        "Name": "mini_chromium",
        "URL": "https://chromium.googlesource.com/chromium/mini_chromium/",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'crashpad', 'crashpad', 'third_party', 'xnu'): {
        "Name": "xnu",
        "URL": "https://opensource.apple.com/source/xnu/",
        "License": "Apple Public Source License 2.0",
        "License File": "APPLE_LICENSE",
    },
    os.path.join('third_party', 'crashpad', 'crashpad', 'third_party', 'zlib'):
    {
        "Name": "zlib",
        "URL": "https://zlib.net/",
        "License": "zlib",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'v8-i18n'): {
        "Name": "Internationalization Library for v8",
        "URL": "http://code.google.com/p/v8-i18n/",
        "License": "Apache 2.0",
    },
    os.path.join('third_party', 'blink'): {
        # about:credits doesn't show "Blink" but "WebKit".
        # Blink is a fork of WebKit, and Chromium project has maintained it
        # since the fork.  about:credits needs to mention the code before
        # the fork.
        "Name": "WebKit",
        "URL": "http://webkit.org/",
        "License": "BSD and LGPL v2 and LGPL v2.1",
        # Absolute path here is resolved as relative to the source root.
        "License File": "/third_party/blink/LICENSE_FOR_ABOUT_CREDITS",
    },
    os.path.join('third_party', 'webpagereplay'): {
        "Name": "webpagereplay",
        "URL": "http://code.google.com/p/web-page-replay",
        "License": "Apache 2.0",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('tools', 'gyp'): {
        "Name": "gyp",
        "URL": "http://code.google.com/p/gyp",
        "License": "BSD",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('v8'): {
        "Name": "V8 JavaScript Engine",
        "URL": "http://code.google.com/p/v8",
        "License": "BSD",
    },
    os.path.join('v8', 'strongtalk'): {
        "Name": "Strongtalk",
        "URL": "http://www.strongtalk.org/",
        "License": "BSD",
        # Absolute path here is resolved as relative to the source root.
        "License File": "/v8/LICENSE.strongtalk",
    },
    os.path.join('v8', 'fdlibm'): {
        "Name": "fdlibm",
        "URL": "http://www.netlib.org/fdlibm/",
        "License": "Freely Distributable",
        # Absolute path here is resolved as relative to the source root.
        "License File": "/v8/LICENSE.fdlibm",
        "License Android Compatible": "yes",
    },
    os.path.join('third_party', 'khronos_glcts'): {
        # These sources are not shipped, are not public, and it isn't
        # clear why they're tripping the license check.
        "Name": "khronos_glcts",
        "URL": "http://no-public-url",
        "License": "Khronos",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('tools', 'telemetry', 'third_party', 'gsutil'): {
        "Name": "gsutil",
        "URL": "https://cloud.google.com/storage/docs/gsutil",
        "License": "Apache 2.0",
        "License File": "NOT_SHIPPED",
    },
    os.path.join('third_party', 'swiftshader'): {
        "Name": "SwiftShader",
        "URL": "https://swiftshader.googlesource.com/SwiftShader",
        "License": "Apache 2.0 and compatible licenses",
        "License Android Compatible": "yes",
        "License File": "/third_party/swiftshader/LICENSE.txt",
    },
}

# Special value for 'License File' field used to indicate that the license file
# should not be used in about:credits.
NOT_SHIPPED = "NOT_SHIPPED"

# Paths for libraries that we have checked are not shipped on iOS. These are
# left out of the licenses file primarily because we don't want to cause a
# firedrill due to someone thinking that Chrome for iOS is using LGPL code
# when it isn't.
# This is a temporary hack; the real solution is crbug.com/178215
KNOWN_NON_IOS_LIBRARIES = set([
    os.path.join('base', 'third_party', 'symbolize'),
    os.path.join('base', 'third_party', 'xdg_mime'),
    os.path.join('base', 'third_party', 'xdg_user_dirs'),
    os.path.join('buildtools', 'third_party', 'libc++'),
    os.path.join('buildtools', 'third_party', 'libc++abi'),
    os.path.join('chrome', 'installer', 'mac', 'third_party', 'bsdiff'),
    os.path.join('chrome', 'installer', 'mac', 'third_party', 'xz'),
    os.path.join('chrome', 'test', 'data', 'third_party', 'kraken'),
    os.path.join('chrome', 'test', 'data', 'third_party', 'spaceport'),
    os.path.join('chrome', 'third_party', 'mozilla_security_manager'),
    os.path.join('third_party', 'angle'),
    os.path.join('third_party', 'apple_apsl'),
    os.path.join('third_party', 'apple_sample_code'),
    os.path.join('third_party', 'ashmem'),
    os.path.join('third_party', 'blink'),
    os.path.join('third_party', 'bspatch'),
    os.path.join('third_party', 'cld'),
    os.path.join('third_party', 'flot'),
    os.path.join('third_party', 'gtk+'),
    os.path.join('third_party', 'iaccessible2'),
    os.path.join('third_party', 'iccjpeg'),
    os.path.join('third_party', 'isimpledom'),
    os.path.join('third_party', 'jsoncpp'),
    os.path.join('third_party', 'khronos'),
    os.path.join('third_party', 'libXNVCtrl'),
    os.path.join('third_party', 'libevent'),
    os.path.join('third_party', 'libjpeg'),
    os.path.join('third_party', 'libusb'),
    os.path.join('third_party', 'libxslt'),
    os.path.join('third_party', 'lss'),
    os.path.join('third_party', 'lzma_sdk'),
    os.path.join('third_party', 'mesa'),
    os.path.join('third_party', 'motemplate'),
    os.path.join('third_party', 'mozc'),
    os.path.join('third_party', 'mozilla'),
    os.path.join('third_party', 'npapi'),
    os.path.join('third_party', 'ots'),
    os.path.join('third_party', 'perfetto'),
    os.path.join('third_party', 'ppapi'),
    os.path.join('third_party', 'qcms'),
    os.path.join('third_party', 're2'),
    os.path.join('third_party', 'safe_browsing'),
    os.path.join('third_party', 'smhasher'),
    os.path.join('third_party', 'sudden_motion_sensor'),
    os.path.join('third_party', 'swiftshader'),
    os.path.join('third_party', 'swig'),
    os.path.join('third_party', 'talloc'),
    os.path.join('third_party', 'tcmalloc'),
    os.path.join('third_party', 'usb_ids'),
    os.path.join('third_party', 'v8-i18n'),
    os.path.join('third_party', 'wtl'),
    os.path.join('third_party', 'yasm'),
    os.path.join('v8', 'strongtalk'),
])


class LicenseError(Exception):
  """We raise this exception when a directory's licensing info isn't
    fully filled out."""
  pass


def AbsolutePath(path, filename, root):
  """Convert a path in README.chromium to be absolute based on the source
    root."""
  if filename.startswith('/'):
    # Absolute-looking paths are relative to the source root
    # (which is the directory we're run from).
    absolute_path = os.path.join(root, filename[1:])
  else:
    absolute_path = os.path.join(root, path, filename)
  if os.path.exists(absolute_path):
    return absolute_path
  return None


def ParseDir(path, root, require_license_file=True, optional_keys=None):
  """Examine a third_party/foo component and extract its metadata."""
  # Parse metadata fields out of README.chromium.
  # We examine "LICENSE" for the license file by default.
  metadata = {
      "License File": "LICENSE",  # Relative path to license text.
      "Name": None,  # Short name (for header on about:credits).
      "URL": None,  # Project home page.
      "License": None,  # Software license.
  }

  if optional_keys is None:
    optional_keys = []

  if path in SPECIAL_CASES:
    metadata.update(SPECIAL_CASES[path])
  else:
    # Try to find README.chromium.
    readme_path = os.path.join(root, path, 'README.chromium')
    if not os.path.exists(readme_path):
      raise LicenseError("missing README.chromium or licenses.py "
                         "SPECIAL_CASES entry in %s\n" % path)

    for line in codecs.open(readme_path, encoding='utf-8'):
      line = line.strip()
      if not line:
        break
      for key in list(metadata.keys()) + optional_keys:
        field = key + ": "
        if line.startswith(field):
          metadata[key] = line[len(field):]

  # Check that all expected metadata is present.
  errors = []
  for key, value in metadata.items():
    if not value:
      errors.append("couldn't find '" + key + "' line "
                    "in README.chromium or licences.py "
                    "SPECIAL_CASES")

  # Special-case modules that aren't in the shipping product, so don't need
  # their license in about:credits.
  if metadata["License File"] != NOT_SHIPPED:
    # Check that the license file exists.
    for filename in (metadata["License File"], "COPYING"):
      license_path = AbsolutePath(path, filename, root)
      if license_path is not None:
        break

    if require_license_file and not license_path:
      errors.append("License file not found. "
                    "Either add a file named LICENSE, "
                    "import upstream's COPYING if available, "
                    "or add a 'License File:' line to "
                    "README.chromium with the appropriate path.")
    metadata["License File"] = license_path

  if errors:
    raise LicenseError("Errors in %s:\n %s\n" % (path, ";\n ".join(errors)))
  return metadata


def ContainsFiles(path, root):
  """Determines whether any files exist in a directory or in any of its
    subdirectories."""
  for _, dirs, files in os.walk(os.path.join(root, path)):
    if files:
      return True
    for vcs_metadata in VCS_METADATA_DIRS:
      if vcs_metadata in dirs:
        dirs.remove(vcs_metadata)
  return False


def FilterDirsWithFiles(dirs_list, root):
  # If a directory contains no files, assume it's a DEPS directory for a
  # project not used by our current configuration and skip it.
  return [x for x in dirs_list if ContainsFiles(x, root)]


def ProcessAdditionalReadmePathsJson(root, dirname, third_party_dirs):
  """For a given directory, process the additional readme paths, and add to
    third_party_dirs."""
  additional_paths_file = os.path.join(root, dirname, ADDITIONAL_PATHS_FILENAME)
  if os.path.exists(additional_paths_file):
    with codecs.open(additional_paths_file, encoding='utf-8') as paths_file:
      extra_paths = json.load(paths_file)
      third_party_dirs.update([os.path.join(dirname, p) for p in extra_paths])


def FindThirdPartyDirs(prune_paths, root, extra_third_party_dirs=None):
  """Find all third_party directories underneath the source root."""
  third_party_dirs = set()
  for path, dirs, files in os.walk(root):
    path = path[len(root) + 1:]  # Pretty up the path.

    # .gitignore ignores /out*/, so do the same here.
    if path in prune_paths or path.startswith('out'):
      dirs[:] = []
      continue

    # Prune out directories we want to skip.
    # (Note that we loop over PRUNE_DIRS so we're not iterating over a
    # list that we're simultaneously mutating.)
    for skip in PRUNE_DIRS:
      if skip in dirs:
        dirs.remove(skip)

    if os.path.basename(path) == 'third_party':
      # Add all subdirectories that are not marked for skipping.
      for dir in dirs:
        dirpath = os.path.join(path, dir)
        if dirpath not in prune_paths:
          third_party_dirs.add(dirpath)

        ProcessAdditionalReadmePathsJson(root, dirpath, third_party_dirs)

      # Don't recurse into any subdirs from here.
      dirs[:] = []
      continue

    # Don't recurse into paths in ADDITIONAL_PATHS, like we do with regular
    # third_party/foo paths.
    if path in ADDITIONAL_PATHS:
      dirs[:] = []

  extra_paths = set(ADDITIONAL_PATHS)
  if extra_third_party_dirs:
    extra_paths.update(extra_third_party_dirs)

  for dir in extra_paths:
    if dir not in prune_paths:
      third_party_dirs.add(dir)
      ProcessAdditionalReadmePathsJson(root, dir, third_party_dirs)

  return sorted(third_party_dirs)


def FindThirdPartyDirsWithFiles(root):
  third_party_dirs = FindThirdPartyDirs(PRUNE_PATHS, root)
  return FilterDirsWithFiles(third_party_dirs, root)


# Many builders do not contain 'gn' in their PATH, so use the GN binary from
# //buildtools.
def _GnBinary():
  exe = 'gn'
  if sys.platform.startswith('linux'):
    subdir = 'linux64'
  elif sys.platform == 'darwin':
    subdir = 'mac'
  elif sys.platform == 'win32':
    subdir, exe = 'win', 'gn.exe'
  else:
    raise RuntimeError("Unsupported platform '%s'." % sys.platform)

  return os.path.join(_REPOSITORY_ROOT, 'buildtools', subdir, exe)


def GetThirdPartyDepsFromGNDepsOutput(gn_deps, target_os):
  """Returns third_party/foo directories given the output of "gn desc deps".

    Note that it always returns the direct sub-directory of third_party
    where README.chromium and LICENSE files are, so that it can be passed to
    ParseDir(). e.g.:
        third_party/cld_3/src/src/BUILD.gn -> third_party/cld_3

    It returns relative paths from _REPOSITORY_ROOT, not absolute paths.
    """
  third_party_deps = set()
  for absolute_build_dep in gn_deps.split():
    relative_build_dep = os.path.relpath(absolute_build_dep, _REPOSITORY_ROOT)
    m = re.search(
        r'^((.+[/\\])?third_party[/\\][^/\\]+[/\\])(.+[/\\])?BUILD\.gn$',
        relative_build_dep)
    if not m:
      continue
    third_party_path = m.group(1)
    if any(third_party_path.startswith(p + os.sep) for p in PRUNE_PATHS):
      continue
    if (target_os == 'ios' and any(
        third_party_path.startswith(p + os.sep)
        for p in KNOWN_NON_IOS_LIBRARIES)):
      # Skip over files that are known not to be used on iOS.
      continue
    third_party_deps.add(third_party_path[:-1])
  return sorted(third_party_deps)


def FindThirdPartyDeps(gn_out_dir, gn_target, target_os):
  if not gn_out_dir:
    raise RuntimeError("--gn-out-dir is required if --gn-target is used.")

  # Generate gn project in temp directory and use it to find dependencies.
  # Current gn directory cannot be used when we run this script in a gn action
  # rule, because gn doesn't allow recursive invocations due to potential side
  # effects.
  tmp_dir = None
  try:
    tmp_dir = tempfile.mkdtemp(dir=gn_out_dir)
    shutil.copy(os.path.join(gn_out_dir, "args.gn"), tmp_dir)
    subprocess.check_output([_GnBinary(), "gen", tmp_dir])
    gn_deps = subprocess.check_output([
        _GnBinary(), "desc", tmp_dir, gn_target, "deps", "--as=buildfile",
        "--all"
    ])
    if isinstance(gn_deps, bytes):
      gn_deps = gn_deps.decode("utf-8")
  finally:
    if tmp_dir and os.path.exists(tmp_dir):
      shutil.rmtree(tmp_dir)

  return GetThirdPartyDepsFromGNDepsOutput(gn_deps, target_os)


def ScanThirdPartyDirs(root=None):
  """Scan a list of directories and report on any problems we find."""
  if root is None:
    root = os.getcwd()
  third_party_dirs = FindThirdPartyDirsWithFiles(root)

  errors = []
  for path in sorted(third_party_dirs):
    try:
      metadata = ParseDir(path, root)
    except LicenseError as e:
      errors.append((path, e.args[0]))
      continue

  for path, error in sorted(errors):
    print(path + ": " + error)

  return len(errors) == 0


def GenerateCredits(file_template_file,
                    entry_template_file,
                    output_file,
                    target_os,
                    gn_out_dir,
                    gn_target,
                    extra_third_party_dirs=None,
                    depfile=None):
  """Generate about:credits."""

  def EvaluateTemplate(template, env, escape=True):
    """Expand a template with variables like {{foo}} using a
        dictionary of expansions."""
    for key, val in env.items():
      if escape:
        val = html.escape(val)
      template = template.replace('{{%s}}' % key, val)
    return template

  def MetadataToTemplateEntry(metadata, entry_template):
    env = {
        'name': metadata['Name'],
        'url': metadata['URL'],
        'license': codecs.open(metadata['License File'],
                               encoding='utf-8').read(),
    }
    return {
        'name': metadata['Name'],
        'content': EvaluateTemplate(entry_template, env),
        'license_file': metadata['License File'],
    }

  if gn_target:
    third_party_dirs = FindThirdPartyDeps(gn_out_dir, gn_target, target_os)

    # Sanity-check to raise a build error if invalid gn_... settings are
    # somehow passed to this script.
    if not third_party_dirs:
      raise RuntimeError("No deps found.")
  else:
    third_party_dirs = FindThirdPartyDirs(PRUNE_PATHS, _REPOSITORY_ROOT,
                                          extra_third_party_dirs)

  if not file_template_file:
    file_template_file = os.path.join(_REPOSITORY_ROOT, 'components',
                                      'about_ui', 'resources',
                                      'about_credits.tmpl')
  if not entry_template_file:
    entry_template_file = os.path.join(_REPOSITORY_ROOT, 'components',
                                       'about_ui', 'resources',
                                       'about_credits_entry.tmpl')

  entry_template = codecs.open(entry_template_file, encoding='utf-8').read()
  entries = []
  # Start from Chromium's LICENSE file
  chromium_license_metadata = {
      'Name': 'The Chromium Project',
      'URL': 'http://www.chromium.org',
      'License File': os.path.join(_REPOSITORY_ROOT, 'LICENSE')
  }
  entries.append(
      MetadataToTemplateEntry(chromium_license_metadata, entry_template))

  entries_by_name = {}
  for path in third_party_dirs:
    try:
      metadata = ParseDir(path, _REPOSITORY_ROOT)
    except LicenseError:
      # TODO(phajdan.jr): Convert to fatal error (http://crbug.com/39240).
      continue
    if metadata['License File'] == NOT_SHIPPED:
      continue
    if target_os == 'ios' and not gn_target:
      # Skip over files that are known not to be used on iOS. But
      # skipping is unnecessary if GN was used to query the actual
      # dependencies.
      # TODO(lambroslambrou): Remove this step once the iOS build is
      # updated to provide --gn-target to this script.
      if path in KNOWN_NON_IOS_LIBRARIES:
        continue

    new_entry = MetadataToTemplateEntry(metadata, entry_template)
    # Skip entries that we've already seen (it exists in multiple directories).
    prev_entry = entries_by_name.setdefault(new_entry['name'], new_entry)
    if prev_entry is not new_entry and (
        prev_entry['content'] == new_entry['content']):
      continue

    entries.append(new_entry)

  entries.sort(key=lambda entry: (entry['name'].lower(), entry['content']))
  for entry_id, entry in enumerate(entries):
    entry['content'] = entry['content'].replace('{{id}}', str(entry_id))

  entries_contents = '\n'.join([entry['content'] for entry in entries])
  file_template = codecs.open(file_template_file, encoding='utf-8').read()
  template_contents = "<!-- Generated by licenses.py; do not edit. -->"
  template_contents += EvaluateTemplate(
      file_template, {'entries': entries_contents}, escape=False)

  if output_file:
    changed = True
    try:
      old_output = codecs.open(output_file, 'r', encoding='utf-8').read()
      if old_output == template_contents:
        changed = False
    except:
      pass
    if changed:
      with codecs.open(output_file, 'w', encoding='utf-8') as output:
        output.write(template_contents)
  else:
    print(template_contents)

  if depfile:
    assert output_file
    # Add in build.ninja so that the target will be considered dirty whenever
    # gn gen is run. Otherwise, it will fail to notice new files being added.
    # This is still no perfect, as it will fail if no build files are changed,
    # but a new README.chromium / LICENSE is added. This shouldn't happen in
    # practice however.
    license_file_list = (entry['license_file'] for entry in entries)
    license_file_list = (os.path.relpath(p) for p in license_file_list)
    license_file_list = sorted(set(license_file_list))
    build_utils.WriteDepfile(depfile, output_file,
                             license_file_list + ['build.ninja'])

  return True


def _ReadFile(path):
  """Reads a file from disk.
    Args:
      path: The path of the file to read, relative to the root of the
      repository.
    Returns:
      The contents of the file as a string.
    """
  with codecs.open(os.path.join(_REPOSITORY_ROOT, path), 'r', 'utf-8') as f:
    return f.read()


def GenerateLicenseFile(output_file, gn_out_dir, gn_target, target_os):
  """Generate a plain-text LICENSE file which can be used when you ship a part
    of Chromium code (specified by gn_target) as a stand-alone library
    (e.g., //ios/web_view).

    The LICENSE file contains licenses of both Chromium and third-party
    libraries which gn_target depends on. """

  third_party_dirs = FindThirdPartyDeps(gn_out_dir, gn_target, target_os)

  # Start with Chromium's LICENSE file.
  content = [_ReadFile('LICENSE')]

  # Add necessary third_party.
  for directory in sorted(third_party_dirs):
    metadata = ParseDir(directory, _REPOSITORY_ROOT, require_license_file=True)
    license_file = metadata['License File']
    if license_file and license_file != NOT_SHIPPED:
      content.append('-' * 20)
      content.append(directory.split(os.sep)[-1])
      content.append('-' * 20)
      content.append(_ReadFile(license_file))

  content_text = '\n'.join(content)

  if output_file:
    with codecs.open(output_file, 'w', 'utf-8') as output:
      output.write(content_text)
  else:
    print(content_text)



def main():
  parser = argparse.ArgumentParser()
  parser.add_argument(
      '--file-template', help='Template HTML to use for the license page.')
  parser.add_argument(
      '--entry-template', help='Template HTML to use for each license.')
  parser.add_argument(
      '--extra-third-party-dirs',
      help='Gn list of additional third_party dirs to look through.')
  parser.add_argument('--target-os', help='OS that this build is targeting.')
  parser.add_argument(
      '--gn-out-dir', help='GN output directory for scanning dependencies.')
  parser.add_argument('--gn-target', help='GN target to scan for dependencies.')
  parser.add_argument(
      'command', choices=['help', 'scan', 'credits', 'license_file'])
  parser.add_argument('output_file', nargs='?')
  build_utils.AddDepfileOption(parser)
  args = parser.parse_args()
  args.extra_third_party_dirs = build_utils.ParseGnList(
      args.extra_third_party_dirs)

  if args.command == 'scan':
    if not ScanThirdPartyDirs():
      return 1
  elif args.command == 'credits':
    if not GenerateCredits(args.file_template, args.entry_template,
                           args.output_file, args.target_os, args.gn_out_dir,
                           args.gn_target, args.extra_third_party_dirs,
                           args.depfile):
      return 1
  elif args.command == 'license_file':
    try:
      GenerateLicenseFile(args.output_file, args.gn_out_dir, args.gn_target,
                          args.target_os)
    except LicenseError as e:
      print("Failed to parse README.chromium: {}".format(e))
      return 1
  else:
    print(__doc__)
    return 1


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