[RFC] Add kotlinc option support in toolchain

kotlin/internal/toolchains.bzl

@@ -62,6 +62,7 @@ def _kotlin_toolchain_impl(ctx):
     toolchain = dict(
         language_version = ctx.attr.language_version,
         api_version = ctx.attr.api_version,
+        extra_copts = ctx.attr.extra_copts,
         debug = ctx.attr.debug,
         jvm_target = ctx.attr.jvm_target,
         kotlinbuilder = ctx.attr.kotlinbuilder,
@@ -107,6 +108,10 @@ _kt_toolchain = rule(
                 "1.3",
             ],
         ),
+        "extra_copts": attr.string_list(
+            doc = "The extra options for kotlinc compiler.",
+            allow_empty = True
+        ),
         "debug": attr.string_list(
             doc = """Debugging tags passed to the builder. Two tags are supported. `timings` will cause the builder to
             print timing information. `trace` will cause the builder to print tracing messages. These tags can be
@@ -170,14 +175,16 @@ def define_kt_toolchain(
         name,
         language_version = None,
         api_version = None,
-        jvm_target = None):
+        jvm_target = None,
+        extra_copts = None):
     """Define the Kotlin toolchain."""
     impl_name = name + "_impl"
     _kt_toolchain(
         name = impl_name,
         language_version = language_version,
         api_version = api_version,
         jvm_target = jvm_target,
+        extra_copts = extra_copts,
         debug =
             select({
                 "@io_bazel_rules_kotlin//kotlin/internal:builder_debug_trace": ["trace"],

kotlin/internal/utils/utils.bzl

@@ -36,6 +36,8 @@ def _init_builder_args(ctx, rule_kind, module_name):
     args.add("--kotlin_language_version", toolchain.language_version)
     args.add("--kotlin_passthrough_flags", "-Xuse-experimental=kotlin.Experimental")
 
+    args.add_all("--extra_copts", toolchain.extra_copts)
+
     debug = depset(toolchain.debug)
     for tag in ctx.attr.tags:
         if tag == "trace":

src/main/kotlin/io/bazel/kotlin/builder/tasks/KotlinBuilder.kt

@@ -139,6 +139,7 @@ class KotlinBuilder @Inject internal constructor(
         JS_PASSTHROUGH_FLAGS("--kotlin_js_passthrough_flags"),
         JS_LIBRARIES("--kotlin_js_libraries"),
         DEBUG("--kotlin_debug_tags"),
+        EXTRA_COPTS("--extra_copts"),
         TASK_ID("--kotlin_task_id");
     }
 
@@ -165,6 +166,9 @@ class KotlinBuilder @Inject internal constructor(
             argMap.mandatorySingle(KotlinBuilderFlags.API_VERSION)
         toolchainInfoBuilder.commonBuilder.languageVersion =
             argMap.mandatorySingle(KotlinBuilderFlags.LANGUAGE_VERSION)
+        toolchainInfoBuilder.commonBuilder.addAllExtraCopts(
+            argMap.optional(KotlinBuilderFlags.EXTRA_COPTS) ?: emptyList<String>()
+        )
         this
       }
 

src/main/kotlin/io/bazel/kotlin/builder/tasks/jvm/compilation_task.kt

@@ -41,6 +41,7 @@ internal fun JvmCompilationTask.commonArgs(): CompilationArgs = baseArgs()
       "-Xfriend-paths=${it.joinToString(X_FRIENDS_PATH_SEPARATOR)}"
     }
     .flag("-d", directories.classes)
+    .values(info.toolchainInfo.common.extraCoptsList)
     .givenNotEmpty(info.passthroughFlags) { it.split(" ") }
 
 internal fun JvmCompilationTask.baseArgs(): CompilationArgs = CompilationArgs()

src/main/protobuf/kotlin_model.proto

@@ -31,6 +31,9 @@ message KotlinToolchainInfo {
         // mandatory
         // oneof "enable", "warn" or "error"
         string coroutines = 3;
+        // optional
+        // extra kotlinc options to be passed into compiler
+        repeated string extra_copts = 4;
     }
 
     // Properties specific to the JVM.