License generation script for build_aar.py.

The script is forked from: tools_webrtc/ios/generate_licenses.py

BUG=webrtc:8182

Review-Url: https://codereview.webrtc.org/3011613002
Cr-Commit-Position: refs/heads/master@{#19679}
diff --git a/tools_webrtc/libs/generate_licenses.py b/tools_webrtc/libs/generate_licenses.py
new file mode 100755
index 0000000..b9ca02f
--- /dev/null
+++ b/tools_webrtc/libs/generate_licenses.py
@@ -0,0 +1,153 @@
+#!/usr/bin/env python
+
+#  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+#
+#  Use of this source code is governed by a BSD-style license
+#  that can be found in the LICENSE file in the root of the source
+#  tree. An additional intellectual property rights grant can be found
+#  in the file PATENTS.  All contributing project authors may
+#  be found in the AUTHORS file in the root of the source tree.
+
+"""Generates license markdown for a prebuilt version of WebRTC."""
+
+import sys
+
+import argparse
+import cgi
+import json
+import logging
+import os
+import re
+import subprocess
+
+
+LIB_TO_LICENSES_DICT = {
+    'android_tools': ['third_party/android_tools/LICENSE'],
+    'boringssl': ['third_party/boringssl/src/LICENSE'],
+    'expat': ['third_party/expat/files/COPYING'],
+    'ijar': ['third_party/ijar/LICENSE'],
+    'jsoncpp': ['third_party/jsoncpp/LICENSE'],
+    'libc++': ['buildtools/third_party/libc++/trunk/LICENSE.TXT'],
+    'libc++abi': ['buildtools/third_party/libc++abi/trunk/LICENSE.TXT'],
+    'libevent': ['base/third_party/libevent/LICENSE'],
+    'libjpeg_turbo': ['third_party/libjpeg_turbo/LICENSE.md'],
+    'libsrtp': ['third_party/libsrtp/LICENSE'],
+    'libvpx': ['third_party/libvpx/source/libvpx/LICENSE'],
+    'libyuv': ['third_party/libyuv/LICENSE'],
+    'openmax_dl': ['third_party/openmax_dl/LICENSE'],
+    'opus': ['third_party/opus/src/COPYING'],
+    'protobuf': ['third_party/protobuf/LICENSE'],
+    'usrsctp': ['third_party/usrsctp/LICENSE'],
+    'webrtc': ['webrtc/LICENSE', 'webrtc/LICENSE_THIRD_PARTY'],
+
+    # Compile time dependencies, no license needed:
+    'yasm': [],
+}
+
+SCRIPT_DIR = os.path.dirname(os.path.realpath(sys.argv[0]))
+CHECKOUT_ROOT = os.path.abspath(os.path.join(SCRIPT_DIR, os.pardir, os.pardir))
+WEBRTC_ROOT = os.path.join(CHECKOUT_ROOT, 'webrtc')
+THIRD_PARTY_LIB_REGEX = r'^.*/third_party/([\w+]+).*$'
+
+class LicenseBuilder(object):
+
+  def __init__(self, buildfile_dirs, targets):
+    self.buildfile_dirs = buildfile_dirs
+    self.targets = targets
+
+  @staticmethod
+  def _ParseLibrary(dep):
+    """
+    Returns a regex match containing library name after third_party
+
+    Input one of:
+    //a/b/third_party/libname:c
+    //a/b/third_party/libname:c(//d/e/f:g)
+    //a/b/third_party/libname/c:d(//e/f/g:h)
+
+    Outputs match with libname in group 1 or None if this is not a third_party
+    dependency.
+    """
+    return re.match(THIRD_PARTY_LIB_REGEX, dep)
+
+  @staticmethod
+  def _RunGN(buildfile_dir, target):
+    cmd = ['gn', 'desc', '--all', '--format=json',
+        os.path.abspath(buildfile_dir), target]
+    logging.debug("Running: %r", cmd)
+    output_json = subprocess.check_output(cmd, cwd=CHECKOUT_ROOT)
+    logging.debug("Output: %s", output_json)
+    return output_json
+
+  @staticmethod
+  def _GetThirdPartyLibraries(buildfile_dir, target):
+    output = json.loads(LicenseBuilder._RunGN(buildfile_dir, target))
+    libraries = set()
+    for target in output.values():
+      third_party_matches = (
+          LicenseBuilder._ParseLibrary(dep) for dep in target['deps'])
+      libraries |= set(match.group(1) for match in third_party_matches if match)
+    return libraries
+
+  def GenerateLicenseText(self, output_dir):
+    # Get a list of third_party libs from gn. For fat libraries we must consider
+    # all architectures, hence the multiple buildfile directories.
+    third_party_libs = set()
+    for buildfile in self.buildfile_dirs:
+      for target in self.targets:
+        third_party_libs |= LicenseBuilder._GetThirdPartyLibraries(
+            buildfile, target)
+    assert len(third_party_libs) > 0
+
+    missing_licenses = third_party_libs - set(LIB_TO_LICENSES_DICT.keys())
+    if missing_licenses:
+      error_msg = 'Missing licenses: %s' % ', '.join(missing_licenses)
+      logging.error(error_msg)
+      raise Exception(error_msg)
+
+    # Put webrtc at the front of the list.
+    license_libs = sorted(third_party_libs)
+    license_libs.insert(0, 'webrtc')
+
+    logging.info("List of licenses: %s", ', '.join(license_libs))
+
+    # Generate markdown.
+    output_license_file = open(os.path.join(output_dir, 'LICENSE.md'), 'w+')
+    for license_lib in license_libs:
+      if len(LIB_TO_LICENSES_DICT[license_lib]) == 0:
+        logging.info("Skipping compile time dependency: %s", license_lib)
+        continue # Compile time dependency
+
+      output_license_file.write('# %s\n' % license_lib)
+      output_license_file.write('```\n')
+      for path in LIB_TO_LICENSES_DICT[license_lib]:
+        license_path = os.path.join(CHECKOUT_ROOT, path)
+        with open(license_path, 'r') as license_file:
+          license_text = cgi.escape(license_file.read(), quote=True)
+          output_license_file.write(license_text)
+          output_license_file.write('\n')
+      output_license_file.write('```\n\n')
+
+    output_license_file.close()
+
+
+def main():
+  parser = argparse.ArgumentParser(description='Generate WebRTC LICENSE.md')
+  parser.add_argument('--verbose', action='store_true', default=False,
+                      help='Debug logging.')
+  parser.add_argument('--target', required=True, action='append', default=[],
+                      help='Name of the GN target to generate a license for')
+  parser.add_argument('output_dir',
+                      help='Directory to output LICENSE.md to.')
+  parser.add_argument('buildfile_dirs', nargs="+",
+                      help='Directories containing gn generated ninja files')
+  args = parser.parse_args()
+
+  logging.basicConfig(level=logging.DEBUG if args.verbose else logging.INFO)
+
+  builder = LicenseBuilder(args.buildfile_dirs, args.target)
+  builder.GenerateLicenseText(args.output_dir)
+
+
+if __name__ == '__main__':
+  sys.exit(main())