README documentation on scalapb_proto_library is outdated

[steinar]

README documentation on scalapb_proto_library lists a number of arguments which were moved to scala_proto_toolchain in #700.

The documentation suggest one should do the following to include gRPC:

scalapb_proto_library(
    name='ping_scala',
    deps=[':ping'],
    with_grpc = True,
)

Which will result in an error as with_grpc argument is unexpected for scalapb_proto_library. Instead you must overwrite the toolchain in your BUILD file:

load("@io_bazel_rules_scala//scala_proto:scala_proto_toolchain.bzl", "scala_proto_toolchain")

scala_proto_toolchain(
    name = "scala_proto_toolchain_configuration",
    with_grpc = False,
)

toolchain(
    name = "scalapb_toolchain",
    toolchain = ":scala_proto_toolchain_configuration",
    toolchain_type = "@io_bazel_rules_scala//scala_proto:toolchain_type",
    visibility = ["//visibility:public"],
)

AFAIK this change is not documented anywhere.

[johnynek]

yes that's right. A PR to improve the documentation would be welcomed!