rules_scala

scala rules

This package registers two rules:

These rules have the following characteristics:

• They generate @build_stack_rules_proto//rules/scala:{proto|grpc}_scala_library. Both are thin wrappers around @io_bazel_rules_scala//scala:scala.bzl%scala_library.
• The rule suffix is _scala_library.
• proto_scala_library is generated if the protos have no services, otherwise grpc_scala_library is emitted.
• They merge on srcs and resolve on deps.
• They provide a littany of symbols onto the global resolver, to be theoretically consumed by a separate scala gazelle extension (see provideScalaImports for details).

Example:

gazelle:proto_rule proto_scala_library implementation stackb:rules_proto:proto_scala_library
gazelle:proto_rule proto_scala_library deps @maven//:com_google_protobuf_protobuf_java
gazelle:proto_rule proto_scala_library deps @maven//:com_thesamet_scalapb_lenses_2_12
gazelle:proto_rule proto_scala_library deps @maven//:com_thesamet_scalapb_scalapb_runtime_2_12
gazelle:proto_rule proto_scala_library options --noresolve=scalapb/scalapb.proto
gazelle:proto_rule proto_scala_library options --exclude=package_scala.srcjar
gazelle:proto_rule proto_scala_library visibility //visibility:public

The above configuration declares a proto_scala_library rule that will statically include the thee named deps, and have public visibility.

Consider a proto package that declares "package options" (other proto files in this package are ignored for this example):

syntax = "proto2";

package example.proto;

import "thirdparty/protobuf/scalapb/scalapb.proto";

option (scalapb.options) = {
    scope: PACKAGE
    preserve_unknown_fields: false
};

In the typical case, the following proto_library and proto_compile rules will be generated:

proto_library(
    name = "package_proto",
    srcs = ["package.proto"],
    deps = ["//thirdparty/protobuf/scalapb:scalapb_proto"],
)

proto_compile(
    name = "package_scala_compile",
    outputs = ["package_scala.srcjar"],
    plugins = ["@build_stack_rules_proto//rules/scala:protoc-gen-scala"],
    proto = "package_proto",
    visibility = ["//visibility:public"],
)

However, in this case we do not want to emit a proto_scala_library. Why? Because the package_scala.srcjar in this case will be empty, as the scalapbc plugin does not emit and corresponding JVM code for this degenerate case.

Therefore, the --exclude means "suppress this output from the output list".