Add CommandLineParserAdapter for >=2.13.9

[mbland]

Description

Fixes //third_party/utils/src/test:test_util for Scala 2.13.9 and later by providing a thin scala.tools.cmd.CommandLineParser adapter. Part of #1482.

Motivation

Before this change, building under Scala 2.13.14 produced:

$ bazel build --repo_env=SCALA_VERSION=2.13.14 \
    //third_party/utils/src/test:test_util

ERROR: .../third_party/utils/src/test/BUILD:6:14:
  scala @@//third_party/utils/src/test:test_util failed: (Exit 1):
  scalac failed: error executing Scalac command
  (from target //third_party/utils/src/test:test_util)
  bazel-out/darwin_arm64-opt-exec-ST-d57f47055a04/bin/src/java/io/bazel/rulesscala/scalac/scalac
  @bazel-out/darwin_arm64-fastbuild/bin/third_party/utils/src/test/test_util.jar-0.params

third_party/utils/src/test/io/bazel/rulesscala/utils/TestUtil.scala:10:
  error: object cmd is not a member of package tools
    import scala.tools.cmd.CommandLineParser
                       ^
third_party/utils/src/test/io/bazel/rulesscala/utils/TestUtil.scala:119:
  error: not found: value CommandLineParser
    val options = CommandLineParser.tokenize(compileOptions)
                  ^

Turns out CommandLineParser disappered in Scala 2.13.9, and its Parser replacement is private:

• improve escaped-quote handling in sys.process (CommandLineParser) scala/scala#10057

[WojciechMazur]

It might be unlikely but in theory some other compiler plugin might define the same workaround. Have you maybe considered creating a dedicated proxy explicitly for rulesscala to decrease chances of name clash?

I had this issue recently when starting work on dependency analyzer plugin port to Scala 3. I've defined it there as following:
For Scala 2.13.10+

package scala {
  package rulesscala {
    // proxy to private[scala] compiler API
    object Proxy {
      def tokenize(cmd: String): List[String] = sys.process.Parser.tokenize(cmd)
    }
  }
}

package io.bazel.rulesscala.utils {
  trait CompilerAPICompat {
    def tokenize(cmd: String): List[String] = scala.rulesscala.Proxy.tokenize(cmd)
  }
}

For other versions:

package io.bazel.rulesscala.utils

import scala.tools.cmd.CommandLineParser

trait CompilerAPICompat {
  def tokenize(cmd: String): List[String] = CommandLineParser.tokenize(cmd)
}

Then I've redefined object TestUtil to extend this trait and used a proxy method instead of depending on compiler internals

[mbland]

Oh, this is better. I haven't actually done much Scala in a while, so this approach didn't occur to me, but it's definitely better than monkeypatching scala.tools.cmd.

I didn't see your original code in the existing code base, so I literally copied and pasted it into a new commit (crediting you, of course).

If this should live somewhere else, or you're about to check it in somewhere else (a quick find | xargs grep didn't turn it up), let me know.

[simuons]

Would it be possible to make CompilerAPICompat an object instead of a trait? It's not a big deal I guess, but on the other hand you are adding tokenize to the api of TestUtil and I'm not sure it belongs here.

[mbland]

Done. I was thinking about doing that, too, as I tend to prefer helper objects to mixins for similar reasons.

I also renamed it to CommandLineParserAdapter to reflect the very specific reason for its existence.

[simuons]

Thanks, @mbland!