tools/gen_grpc_build_gn.py

#!/usr/bin/env python3
import json
import os
import subprocess
import sys
from typing import Any, Dict, List
import yaml

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

IGNORE_LIST = set([
    'grpcpp_channelz',
    'grpc++_reflection',
    'benchmark_helpers',
    'boringssl_test_util',
])

SOURCE_SET_TARGET = """
source_set("{name}") {{
  sources = {srcs}
  public_deps = {deps}
  public_configs = ["..:{config_name}"]
  configs -= [ "//gn/standalone:extra_warnings" ]
}}"""


def grpc_relpath(*segments: str) -> str:
  '''From path segments to GRPC root, returns the absolute path.'''
  return os.path.join(ROOT_DIR, 'buildtools', 'grpc', 'src', *segments)


GRPC_GN_HEADER = '''
#
# DO NOT EDIT. AUTOGENERATED file
#
# This file is generated with the command:
# tools/gen_grpc_build_gn.py > buildtools/grpc/BUILD.gn
#

# Prevent the gRPC from being depended upon without explicitly being opted in.
assert(enable_perfetto_grpc)
'''

GRPC_BUILD_YAML = grpc_relpath('build_autogenerated.yaml')
ABSL_GEN_BUILD_YAML = grpc_relpath('src', 'abseil-cpp', 'gen_build_yaml.py')
UPB_GEN_BUILD_YAML = grpc_relpath('src', 'upb', 'gen_build_yaml.py')
BSSL_GEN_BUILD_YAML = grpc_relpath('src', 'boringssl', 'gen_build_yaml.py')


def bazel_label_to_gn_target(dep: str):
  '''Converts a Bazel label name into a gn target name.'''
  if dep == 'libssl':
    return 'boringssl'
  return dep.replace('/', '_').replace(':', '_')


def gen_grpc_dep_yaml(gen_path: str) -> Dict[str, Any]:
  '''Invokes a gen_build_yaml.py file for creating YAML for gRPC deps.'''
  return yaml.safe_load(subprocess.check_output(['python3', gen_path]))


def yaml_to_gn_targets(desc: Dict[str, Any], build_type: str, config_name: str,
                       out: List[str]):
  '''Given a gRPC YAML description of the build graph, generates GN targets.'''
  for lib in desc['libs']:
    if lib['build'] != build_type:
      continue
    if lib['name'] in IGNORE_LIST:
      continue
    srcs = json.dumps([f'src/{file}' for file in lib['src'] + lib['headers']])
    deps = json.dumps(
        [f':{bazel_label_to_gn_target(dep)}' for dep in lib.get('deps', [])])
    source_set_target = SOURCE_SET_TARGET.format(
        name=bazel_label_to_gn_target(lib['name']),
        config_name=config_name,
        srcs=srcs,
        deps=deps)
    out.append(source_set_target)


def main():
  out: List[str] = []

  # Generate absl rules
  absl_yaml = gen_grpc_dep_yaml(ABSL_GEN_BUILD_YAML)
  yaml_to_gn_targets(absl_yaml, 'private', 'grpc_absl_config', out)

  # Generate upb rules
  upb_yaml = gen_grpc_dep_yaml(UPB_GEN_BUILD_YAML)
  yaml_to_gn_targets(upb_yaml, 'all', 'grpc_upb_config', out)

  # Generate boringssl rules
  boringssl_yaml = gen_grpc_dep_yaml(BSSL_GEN_BUILD_YAML)
  yaml_to_gn_targets(boringssl_yaml, 'private', 'grpc_boringssl_config', out)

  # Generate grpc rules
  with open(GRPC_BUILD_YAML, 'r', encoding='utf-8') as f:
    grpc_yaml = yaml.safe_load(f.read())
  yaml_to_gn_targets(grpc_yaml, 'all', 'grpc_internal_config', out)

  print(GRPC_GN_HEADER)
  print('\n'.join(out))
  return 0


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