[FIR] Make FirExtensionRegistrar a proper extension point

After that commit it's allowed to register any FIR plugin using
  existing extension infrastructure (`-Xplugin` CLI argument,
  plugin.xml for IDE plugins, etc)

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/FirKotlinToJvmBytecodeCompiler.kt

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.fir.backend.jvm.FirJvmBackendExtension
 import org.jetbrains.kotlin.fir.checkers.registerExtendedCommonCheckers
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
+import org.jetbrains.kotlin.fir.extensions.FirExtensionRegistrar
 import org.jetbrains.kotlin.fir.java.FirProjectSessionProvider
 import org.jetbrains.kotlin.fir.pipeline.buildFirFromKtFiles
 import org.jetbrains.kotlin.fir.pipeline.convertToIr
@@ -87,6 +88,7 @@ object FirKotlinToJvmBytecodeCompiler {
         val isMultiModuleChunk = chunk.size > 1
 
         // TODO: run lowerings for all modules in the chunk, then run codegen for all modules.
+        val project = (projectEnvironment as? PsiBasedProjectEnvironment)?.project
         for (module in chunk) {
             val moduleConfiguration = projectConfiguration.applyModuleProperties(module, buildFile)
             val context = CompilationContext(
@@ -101,7 +103,8 @@ object FirKotlinToJvmBytecodeCompiler {
                 targetIds,
                 incrementalComponents,
                 extendedAnalysisMode,
-                (projectEnvironment as? PsiBasedProjectEnvironment)?.project?.let { IrGenerationExtension.getInstances(it) } ?: emptyList()
+                firExtensionRegistrars = project?.let { FirExtensionRegistrar.getInstances(it) } ?: emptyList(),
+                irGenerationExtensions = project?.let { IrGenerationExtension.getInstances(it) } ?: emptyList()
             )
             val generationState = context.compileModule() ?: return false
             outputs += generationState
@@ -112,7 +115,7 @@ object FirKotlinToJvmBytecodeCompiler {
         }
 
         return writeOutputs(
-            (projectEnvironment as? PsiBasedProjectEnvironment)?.project,
+            project,
             projectConfiguration,
             chunk,
             outputs.map(Pair<FirResult, GenerationState>::second),
@@ -208,6 +211,7 @@ object FirKotlinToJvmBytecodeCompiler {
                 librariesScope,
                 lookupTracker = moduleConfiguration.get(CommonConfigurationKeys.LOOKUP_TRACKER),
                 providerAndScopeForIncrementalCompilation,
+                firExtensionRegistrars,
                 dependenciesConfigurator = {
                     dependencies(moduleConfiguration.jvmClasspathRoots.map { it.toPath() })
                     dependencies(moduleConfiguration.jvmModularRoots.map { it.toPath() })
@@ -350,6 +354,7 @@ object FirKotlinToJvmBytecodeCompiler {
         val targetIds: List<TargetId>?,
         val incrementalComponents: IncrementalCompilationComponents?,
         val extendedAnalysisMode: Boolean,
+        val firExtensionRegistrars: List<FirExtensionRegistrar>,
         val irGenerationExtensions: Collection<IrGenerationExtension>
     )
 

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/KotlinCoreEnvironment.kt

@@ -82,6 +82,7 @@ import org.jetbrains.kotlin.config.*
 import org.jetbrains.kotlin.extensions.*
 import org.jetbrains.kotlin.extensions.internal.CandidateInterceptor
 import org.jetbrains.kotlin.extensions.internal.TypeResolutionInterceptor
+import org.jetbrains.kotlin.fir.extensions.FirExtensionRegistrar
 import org.jetbrains.kotlin.idea.KotlinFileType
 import org.jetbrains.kotlin.js.translate.extensions.JsSyntheticTranslateExtension
 import org.jetbrains.kotlin.load.kotlin.KotlinBinaryClassCache
@@ -648,6 +649,7 @@ class KotlinCoreEnvironment private constructor(
             TypeResolutionInterceptor.registerExtensionPoint(project)
             CandidateInterceptor.registerExtensionPoint(project)
             DescriptorSerializerPlugin.registerExtensionPoint(project)
+            FirExtensionRegistrar.registerExtensionPoint(project)
         }
 
         internal fun registerExtensionsFromPlugins(project: MockProject, configuration: CompilerConfiguration) {

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/extensions/FirExtensionRegistrar.kt

@@ -5,14 +5,18 @@
 
 package org.jetbrains.kotlin.fir.extensions
 
+import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.SessionConfiguration
 import org.jetbrains.kotlin.fir.analysis.extensions.FirAdditionalCheckersExtension
 import kotlin.reflect.KClass
 
 abstract class FirExtensionRegistrar {
-    companion object {
-        val AVAILABLE_EXTENSIONS = listOf(
+    companion object : ProjectExtensionDescriptor<FirExtensionRegistrar>(
+        name = "org.jetbrains.kotlin.fir.extensions.firExtensionRegistrar",
+        extensionClass = FirExtensionRegistrar::class.java
+    ) {
+        internal val AVAILABLE_EXTENSIONS = listOf(
             FirStatusTransformerExtension::class,
             FirDeclarationGenerationExtension::class,
             FirAdditionalCheckersExtension::class,

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/FirSessionFactory.kt

@@ -84,6 +84,7 @@ object FirSessionFactory {
         librariesScope: AbstractProjectFileSearchScope,
         lookupTracker: LookupTracker?,
         providerAndScopeForIncrementalCompilation: ProviderAndScopeForIncrementalCompilation?,
+        extensionRegistrars: List<FirExtensionRegistrar>,
         dependenciesConfigurator: DependencyListForCliModule.Builder.() -> Unit = {},
         noinline sessionConfigurator: FirSessionConfigurator.() -> Unit = {},
     ): FirSession {
@@ -113,6 +114,7 @@ object FirSessionFactory {
             sourceScope,
             projectEnvironment,
             providerAndScopeForIncrementalCompilation,
+            extensionRegistrars,
             languageVersionSettings = languageVersionSettings,
             lookupTracker = lookupTracker,
             init = sessionConfigurator
@@ -125,6 +127,7 @@ object FirSessionFactory {
         scope: AbstractProjectFileSearchScope,
         projectEnvironment: AbstractProjectEnvironment,
         providerAndScopeForIncrementalCompilation: ProviderAndScopeForIncrementalCompilation?,
+        extensionRegistrars: List<FirExtensionRegistrar>,
         languageVersionSettings: LanguageVersionSettings = LanguageVersionSettingsImpl.DEFAULT,
         lookupTracker: LookupTracker? = null,
         init: FirSessionConfigurator.() -> Unit = {}
@@ -160,6 +163,9 @@ object FirSessionFactory {
             FirSessionConfigurator(this).apply {
                 registerCommonCheckers()
                 registerJvmCheckers()
+                for (extensionRegistrar in extensionRegistrars) {
+                    registerExtensions(extensionRegistrar.configure())
+                }
                 init()
             }.configure()
 

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/FirFrontendFacade.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.cli.jvm.config.jvmModularRoots
 import org.jetbrains.kotlin.config.JVMConfigurationKeys
 import org.jetbrains.kotlin.fir.analysis.FirAnalyzerFacade
 import org.jetbrains.kotlin.fir.checkers.registerExtendedCommonCheckers
+import org.jetbrains.kotlin.fir.extensions.FirExtensionRegistrar
 import org.jetbrains.kotlin.fir.moduleData
 import org.jetbrains.kotlin.fir.session.FirSessionFactory
 import org.jetbrains.kotlin.js.resolve.JsPlatformAnalyzerServices
@@ -91,6 +92,7 @@ class FirFrontendFacade(
             PsiBasedProjectFileSearchScope(librariesScope),
             lookupTracker = null,
             providerAndScopeForIncrementalCompilation = null,
+            extensionRegistrars = FirExtensionRegistrar.getInstances(project),
             dependenciesConfigurator = {
                 dependencies(configuration.jvmModularRoots.map { it.toPath() })
                 dependencies(configuration.jvmClasspathRoots.map { it.toPath() })

compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirBaseDiagnosticsTest.kt

@@ -98,6 +98,7 @@ abstract class AbstractFirBaseDiagnosticsTest : BaseDiagnosticsTest() {
                 librariesScope = PsiBasedProjectFileSearchScope(allProjectScope),
                 lookupTracker = null,
                 providerAndScopeForIncrementalCompilation = null,
+                extensionRegistrars = emptyList()
             ) {
                 configureSession()
                 getFirExtensions()?.let {

compiler/tests-compiler-utils/tests/org/jetbrains/kotlin/fir/SessionTestUtils.kt

@@ -40,6 +40,7 @@ fun createSessionForTests(
     librariesScope,
     lookupTracker = null,
     providerAndScopeForIncrementalCompilation = null,
+    extensionRegistrars = emptyList(),
     dependenciesConfigurator = {
         friendDependencies(friendsPaths)
     }
@@ -65,6 +66,7 @@ fun createSessionForTests(
         PsiBasedProjectFileSearchScope(librariesScope),
         lookupTracker = null,
         providerAndScopeForIncrementalCompilation = null,
+        extensionRegistrars = emptyList(),
         dependenciesConfigurator = {
             friendDependencies(friendsPaths)
         }