add args parser

scalafix/BUILD

@@ -0,0 +1,15 @@
+load("//rules:scala.bzl", "scala_binary")
+
+scala_binary(
+    name = "scalafmt",
+    args = [
+        "--toolchain=",
+        "--opts=:--verbose:--config",
+    ],
+    main_class = "rules_scala3.scalafix.src.Main",
+    scala = "//scala:bootstrap_3",
+    visibility = ["//visibility:public"],
+    deps = [
+        "@rules_scala3//3rdparty/jvm/com/github/scopt",
+    ],
+)

scalafix/src/ArgsConfig.scala

@@ -0,0 +1,43 @@
+package rules_scala3.scalafix.src
+
+import scopt.OParser
+
+case class ArgsConfig(
+  toolchain: Option[String] = None,
+  scalafixOpts: Option[String] = None,
+  targets: Seq[String] = Seq.empty,
+  excludedTargets: Seq[String] = Seq.empty
+)
+
+object ArgsConfig:
+  private val builder = OParser.builder[ArgsConfig]
+  import builder.*
+
+  private val parser = OParser.sequence(
+    programName("scalafix-runner"),
+    head("scalafix-runner", "1.0"),
+
+    help('h', "help").text("Displays this usage text"),
+
+    opt[String]('t', "toolchain")
+      .required()
+      .action((value, config) => config.copy(toolchain = Some(value)))
+      .text("Required. Specifies the toolchain with which targets will be built"),
+
+    opt[String]('o', "opts")
+      .action((value, config) => config.copy(scalafixOpts = Some(value)))
+      .text("Options passed to scalafix as a colon-separated string (e.g., :--verbose:--config)"),
+
+    arg[String]("<target>...")
+      .unbounded()
+      .optional()
+      .action((target, config) => config.copy(targets = config.targets :+ target))
+      .text("Specifies the Bazel targets to be included"),
+
+    checkConfig { config =>
+      val (excluded, included) = config.targets.partition(_.startsWith("-"))
+      Right(config.copy(excludedTargets = excluded.map(_.drop(1)), targets = included))
+    }
+  )
+
+  def parse(args: Seq[String]): Option[ArgsConfig] = OParser.parse(parser, args, ArgsConfig())

scalafix/src/Main.scala

@@ -0,0 +1,5 @@
+package rules_scala3.scalafix.src
+
+object Main:
+  def main(args: Array[String]): Unit =
+    given Vars = ArgsConfig(args.toIndexedSeq).getOrElse(sys.exit(2))