rules/proto_file_utils.bzl

# Copyright (C) 2021 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.

load("@bazel_skylib//lib:paths.bzl", "paths")
load("@bazel_skylib//lib:sets.bzl", "sets")

def _generate_and_declare_output_files(
        ctx,
        file_names,
        type_dictionary):
    ret = {}
    for typ in type_dictionary:
        ret[typ] = []

    for name in file_names:
        short_path = name.short_path
        for typ, ext in type_dictionary.items():
            # prefix with label.name to prevent collisions between targets
            # if proto compliation becomes an aspect, can prefix with output
            # information instead to allow reuse, e.g. multiple cc `lite`
            # libraries containing the same proto file
            out_name = paths.join(ctx.label.name, paths.replace_extension(short_path, ext))
            declared = ctx.actions.declare_file(out_name)
            ret[typ].append(declared)

    return ret

def _generate_jar_proto_action(
        proto_infos,
        protoc,
        ctx,
        out_flags = [],
        plugin_executable = None,
        out_arg = None,
        mnemonic = "ProtoGen"):
    jar_basename = ctx.label.name + "-proto_gen"
    jar_name = jar_basename + "-src.jar"
    jar_file = ctx.actions.declare_file(jar_name)

    _generate_proto_action(
        proto_infos = proto_infos,
        protoc = protoc,
        ctx = ctx,
        out_flags = out_flags,
        plugin_executable = plugin_executable,
        out_arg = out_arg,
        mnemonic = mnemonic,
        output_file = jar_file,
    )

    srcjar_name = jar_basename + ".srcjar"
    srcjar_file = ctx.actions.declare_file(srcjar_name)
    ctx.actions.symlink(
        output = srcjar_file,
        target_file = jar_file,
    )

    return srcjar_file

def _generate_proto_action(
        proto_infos,
        protoc,
        ctx,
        type_dictionary = None,
        out_flags = [],
        plugin_executable = None,
        out_arg = None,
        mnemonic = "ProtoGen",
        output_file = None):
    """ Utility function for creating proto_compiler action.

    Args:
      proto_infos: A list of ProtoInfo.
      protoc: proto compiler executable.
      ctx: context, used for declaring new files only.
      type_dictionary: a dictionary of types to output extensions
      out_flags: protoc output flags
      plugin_executable: plugin executable file
      out_arg: as appropriate, if plugin_executable and out_arg are both supplied, plugin_executable is preferred
      mnemonic: (optional) a string to describe the proto compilation action
      output_file: (optional) File, used to specify a specific file for protoc output (typically a JAR file)

    Returns:
      Dictionary with declared files grouped by type from the type_dictionary.
    """

    # TODO(B/245629074): Don't build external/protobuf if it is provided in
    #  toolchain already.
    proto_srcs = []
    proto_source_root_list = sets.make()
    transitive_proto_srcs_list = []
    transitive_proto_path_list = sets.make()

    for proto_info in proto_infos:
        sets.insert(proto_source_root_list, proto_info.proto_source_root)
        proto_srcs.extend(proto_info.direct_sources)
        transitive_proto_srcs_list.append(proto_info.transitive_imports)
        for p in proto_info.transitive_proto_path.to_list():
            sets.insert(transitive_proto_path_list, p)

    protoc_out_name = paths.join(ctx.bin_dir.path, ctx.label.package)
    if output_file:
        protoc_out_name = paths.join(protoc_out_name, output_file.basename)
        out_files = {
            "out": [output_file],
        }
    else:
        protoc_out_name = paths.join(protoc_out_name, ctx.label.name)
        out_files = _generate_and_declare_output_files(
            ctx,
            proto_srcs,
            type_dictionary,
        )

    tools = []
    args = ctx.actions.args()
    if plugin_executable:
        tools.append(plugin_executable)
        args.add("--plugin=protoc-gen-PLUGIN=" + plugin_executable.path)
        args.add("--PLUGIN_out=" + ",".join(out_flags) + ":" + protoc_out_name)
    else:
        args.add("{}={}:{}".format(out_arg, ",".join(out_flags), protoc_out_name))

    # the order matters so we add the source roots first
    args.add_all(["-I" + p for p in sets.to_list(proto_source_root_list)])

    args.add_all(["-I" + p for p in sets.to_list(transitive_proto_path_list)])
    args.add_all(["-I{0}={1}".format(f.short_path, f.path) for t in transitive_proto_srcs_list for f in t.to_list()])

    args.add_all([f.short_path for f in proto_srcs])

    inputs = depset(
        direct = proto_srcs,
        transitive = transitive_proto_srcs_list,
    )

    outputs = []
    for outs in out_files.values():
        outputs.extend(outs)

    ctx.actions.run(
        inputs = inputs,
        executable = protoc,
        tools = tools,
        outputs = outputs,
        arguments = [args],
        mnemonic = mnemonic,
    )
    return out_files

proto_file_utils = struct(
    generate_proto_action = _generate_proto_action,
    generate_jar_proto_action = _generate_jar_proto_action,
)