Kotlin 2.4.0: Fix plugin service file to be version-conditional

The CompilerPluginRegistrar service file must only be included in the
2.4.0 jar. Older Kotlin versions (2.3.x and below) read this service
file and try to cast the class to CompilerPluginRegistrar, but the
older version extractor only implements ComponentRegistrar, causing a
ClassCastException at runtime.

For 2.4.0, the registrar implements both ComponentRegistrar (no-op, as
extensionArea was removed) and CompilerPluginRegistrar (actual
registration via ExtensionStorage).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andersfugmann

java/kotlin-extractor/BUILD.bazel

@@ -64,8 +64,14 @@ _resources = [
         r[len("src/main/resources/"):],
     )
     for r in glob(["src/main/resources/**"])
+    if r != "src/main/resources/META-INF/services/org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar"
 ]
 
+_compiler_plugin_registrar_service = (
+    "src/main/resources/META-INF/services/org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar",
+    "META-INF/services/org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar",
+)
+
 kt_javac_options(
     name = "javac-options",
     release = "8",
@@ -91,19 +97,26 @@ kt_javac_options(
         # * `resource_strip_prefix` is unique per jar, so we must also put other resources under the same version prefix
         genrule(
             name = "resources-%s" % v,
-            srcs = [src for src, _ in _resources],
+            srcs = [src for src, _ in _resources] + (
+                [_compiler_plugin_registrar_service[0]] if not version_less(v, "2.4.0") else []
+            ),
             outs = [
                 "%s/com/github/codeql/extractor.name" % v,
             ] + [
                 "%s/%s" % (v, target)
                 for _, target in _resources
-            ],
+            ] + (
+                ["%s/%s" % (v, _compiler_plugin_registrar_service[1])] if not version_less(v, "2.4.0") else []
+            ),
             cmd = "\n".join([
                 "echo %s-%s > $(RULEDIR)/%s/com/github/codeql/extractor.name" % (_extractor_name_prefix, v, v),
             ] + [
                 "cp $(execpath %s) $(RULEDIR)/%s/%s" % (source, v, target)
                 for source, target in _resources
-            ]),
+            ] + (
+                ["cp $(execpath %s) $(RULEDIR)/%s/%s" % (_compiler_plugin_registrar_service[0], v, _compiler_plugin_registrar_service[1])]
+                if not version_less(v, "2.4.0") else []
+            )),
         ),
         kt_jvm_library(
             name = "%s-%s" % (_extractor_name_prefix, v),

java/kotlin-extractor/src/main/kotlin/utils/versions/v_2_4_0/Kotlin2ComponentRegistrar.kt

@@ -1,21 +1,34 @@
-@file:Suppress("DEPRECATION")
+@file:Suppress("DEPRECATION", "DEPRECATION_ERROR")
 @file:OptIn(ExperimentalCompilerApi::class)
 
 package com.github.codeql
 
+import com.intellij.mock.MockProject
 import org.jetbrains.kotlin.backend.common.extensions.IrGenerationExtension
+import org.jetbrains.kotlin.compiler.plugin.ComponentRegistrar
 import org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar
 import org.jetbrains.kotlin.compiler.plugin.ExperimentalCompilerApi
 import org.jetbrains.kotlin.config.CompilerConfiguration
 
-abstract class Kotlin2ComponentRegistrar : CompilerPluginRegistrar() {
+abstract class Kotlin2ComponentRegistrar : CompilerPluginRegistrar(), ComponentRegistrar {
     override val supportsK2: Boolean
         get() = true
 
     override val pluginId: String
         get() = "com.github.codeql.kotlin-extractor"
 
+    // ComponentRegistrar implementation (legacy path, still called by Kotlin compiler)
+    override fun registerProjectComponents(
+        project: MockProject,
+        configuration: CompilerConfiguration
+    ) {
+        // In 2.4.0, we use CompilerPluginRegistrar path instead.
+        // This is only called if the compiler uses the ComponentRegistrar service file.
+        // We do nothing here since registerExtensions will be called separately.
+    }
+
     private var extensionStorage: CompilerPluginRegistrar.ExtensionStorage? = null
+    private var registeredExtension: IrGenerationExtension? = null
 
     override fun ExtensionStorage.registerExtensions(configuration: CompilerConfiguration) {
         this@Kotlin2ComponentRegistrar.extensionStorage = this