grpc/bazel/protobuf.bzl

"""Utility functions for generating protobuf code."""

_PROTO_EXTENSION = ".proto"
_VIRTUAL_IMPORTS = "/_virtual_imports/"


def well_known_proto_libs():
    return [
        "@com_google_protobuf//:any_proto",
        "@com_google_protobuf//:api_proto",
        "@com_google_protobuf//:compiler_plugin_proto",
        "@com_google_protobuf//:descriptor_proto",
        "@com_google_protobuf//:duration_proto",
        "@com_google_protobuf//:empty_proto",
        "@com_google_protobuf//:field_mask_proto",
        "@com_google_protobuf//:source_context_proto",
        "@com_google_protobuf//:struct_proto",
        "@com_google_protobuf//:timestamp_proto",
        "@com_google_protobuf//:type_proto",
        "@com_google_protobuf//:wrappers_proto",
    ]

def get_proto_root(workspace_root):
    """Gets the root protobuf directory.

    Args:
      workspace_root: context.label.workspace_root

    Returns:
      The directory relative to which generated include paths should be.
    """
    if workspace_root:
        return "/{}".format(workspace_root)
    else:
        return ""

def _strip_proto_extension(proto_filename):
    if not proto_filename.endswith(_PROTO_EXTENSION):
        fail('"{}" does not end with "{}"'.format(
            proto_filename,
            _PROTO_EXTENSION,
        ))
    return proto_filename[:-len(_PROTO_EXTENSION)]

def proto_path_to_generated_filename(proto_path, fmt_str):
    """Calculates the name of a generated file for a protobuf path.

    For example, "examples/protos/helloworld.proto" might map to
      "helloworld.pb.h".

    Args:
      proto_path: The path to the .proto file.
      fmt_str: A format string used to calculate the generated filename. For
        example, "{}.pb.h" might be used to calculate a C++ header filename.

    Returns:
      The generated filename.
    """
    return fmt_str.format(_strip_proto_extension(proto_path))

def get_include_directory(source_file):
    """Returns the include directory path for the source_file. I.e. all of the
    include statements within the given source_file are calculated relative to
    the directory returned by this method.

    The returned directory path can be used as the "--proto_path=" argument
    value.

    Args:
      source_file: A proto file.

    Returns:
      The include directory path for the source_file.
    """
    directory = source_file.path
    prefix_len = 0

    if is_in_virtual_imports(source_file):
        root, relative = source_file.path.split(_VIRTUAL_IMPORTS, 2)
        result = root + _VIRTUAL_IMPORTS + relative.split("/", 1)[0]
        return result

    if not source_file.is_source and directory.startswith(source_file.root.path):
        prefix_len = len(source_file.root.path) + 1

    if directory.startswith("external", prefix_len):
        external_separator = directory.find("/", prefix_len)
        repository_separator = directory.find("/", external_separator + 1)
        return directory[:repository_separator]
    else:
        return source_file.root.path if source_file.root.path else "."

def get_plugin_args(plugin, flags, dir_out, generate_mocks):
    """Returns arguments configuring protoc to use a plugin for a language.

    Args:
      plugin: An executable file to run as the protoc plugin.
      flags: The plugin flags to be passed to protoc.
      dir_out: The output directory for the plugin.
      generate_mocks: A bool indicating whether to generate mocks.

    Returns:
      A list of protoc arguments configuring the plugin.
    """
    augmented_flags = list(flags)
    if generate_mocks:
        augmented_flags.append("generate_mock_code=true")
    return [
        "--plugin=protoc-gen-PLUGIN=" + plugin.path,
        "--PLUGIN_out=" + ",".join(augmented_flags) + ":" + dir_out,
    ]

def _get_staged_proto_file(context, source_file):
    if source_file.dirname == context.label.package \
        or is_in_virtual_imports(source_file):
        # Current target and source_file are in same package
        return source_file
    else:
        # Current target and source_file are in different packages (most
        # probably even in different repositories)
        copied_proto = context.actions.declare_file(source_file.basename)
        context.actions.run_shell(
            inputs = [source_file],
            outputs = [copied_proto],
            command = "cp {} {}".format(source_file.path, copied_proto.path),
            mnemonic = "CopySourceProto",
        )
        return copied_proto

def protos_from_context(context):
    """Copies proto files to the appropriate location.

    Args:
      context: The ctx object for the rule.

    Returns:
      A list of the protos.
    """
    protos = []
    for src in context.attr.deps:
        for file in src[ProtoInfo].direct_sources:
            protos.append(_get_staged_proto_file(context, file))
    return protos

def includes_from_deps(deps):
    """Get includes from rule dependencies."""
    return [
        file
        for src in deps
        for file in src[ProtoInfo].transitive_imports.to_list()
    ]

def get_proto_arguments(protos, genfiles_dir_path):
    """Get the protoc arguments specifying which protos to compile."""
    arguments = []
    for proto in protos:
        massaged_path = proto.path
        if is_in_virtual_imports(proto):
            incl_directory = get_include_directory(proto)
            if massaged_path.startswith(incl_directory):
                massaged_path = massaged_path[len(incl_directory) + 1:]
        elif massaged_path.startswith(genfiles_dir_path):
            massaged_path = proto.path[len(genfiles_dir_path) + 1:]
        arguments.append(massaged_path)

    return arguments

def declare_out_files(protos, context, generated_file_format):
    """Declares and returns the files to be generated."""

    out_file_paths = []
    for proto in protos:
        if not is_in_virtual_imports(proto):
            out_file_paths.append(proto.basename)
        else:
            path = proto.path[proto.path.index(_VIRTUAL_IMPORTS) + 1:]
            # TODO: uncomment if '.' path is chosen over
            #       `_virtual_imports/proto_library_target_name` as the output
            # path = proto.path.split(_VIRTUAL_IMPORTS)[1].split("/", 1)[1]
            out_file_paths.append(path)


    return [
        context.actions.declare_file(
            proto_path_to_generated_filename(
                out_file_path,
                generated_file_format,
            ),
        )
        for out_file_path in out_file_paths
    ]

def get_out_dir(protos, context):
    """ Returns the calcualted value for --<lang>_out= protoc argument based on
    the input source proto files and current context.

    Args:
        protos: A list of protos to be used as source files in protoc command
        context: A ctx object for the rule.
    Returns:
        The value of --<lang>_out= argument.
    """
    at_least_one_virtual = 0
    for proto in protos:
        if is_in_virtual_imports(proto):
            at_least_one_virtual = True
        elif at_least_one_virtual:
            fail("Proto sources must be either all virtual imports or all real")
    if at_least_one_virtual:
        return get_include_directory(protos[0])
        # TODO: uncomment if '.' path is chosen over
        #       `_virtual_imports/proto_library_target_name` as the output path
        # return "{}/{}".format(context.genfiles_dir.path, context.label.package)
    return context.genfiles_dir.path

def is_in_virtual_imports(source_file, virtual_folder = _VIRTUAL_IMPORTS):
    """Determines if source_file is virtual (is placed in _virtual_imports
    subdirectory). The output of all proto_library targets which use
    import_prefix  and/or strip_import_prefix arguments is placed under
    _virtual_imports directory.

    Args:
        context: A ctx object for the rule.
        virtual_folder: The virtual folder name (is set to "_virtual_imports"
            by default)
    Returns:
        True if source_file is located under _virtual_imports, False otherwise.
    """
    return not source_file.is_source and virtual_folder in source_file.path