Refactor Main-Class computation in CLI for JVM with .jar outputs

Compute FQ name of the main class right after running the analysis and
before invoking codegen. This is needed because MainFunctionDetector
depends on BindingContext, and JVM IR needs to clear BindingContext as
soon as it's not necessary to reduce peak memory usage, thus breaking
any usages of data from it after the codegen.

Also refactor and use the extracted, but not properly reused previously,
copy of findMainClass in findMainClass.kt.

Note that this replaces NPE in KT-42868 with an UOE.

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

@@ -53,7 +53,6 @@ import org.jetbrains.kotlin.config.*
 import org.jetbrains.kotlin.container.get
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.diagnostics.*
-import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 import org.jetbrains.kotlin.fir.FirPsiSourceElement
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.analysis.FirAnalyzerFacade
@@ -63,7 +62,6 @@ import org.jetbrains.kotlin.fir.backend.jvm.FirMetadataSerializer
 import org.jetbrains.kotlin.fir.checkers.registerExtendedCommonCheckers
 import org.jetbrains.kotlin.fir.java.FirProjectSessionProvider
 import org.jetbrains.kotlin.fir.session.FirSessionFactory
-import org.jetbrains.kotlin.idea.MainFunctionDetector
 import org.jetbrains.kotlin.ir.backend.jvm.jvmResolveLibraries
 import org.jetbrains.kotlin.javac.JavacWrapper
 import org.jetbrains.kotlin.load.kotlin.ModuleVisibilityManager
@@ -88,14 +86,14 @@ object KotlinToJVMBytecodeCompiler {
     private fun writeOutput(
         configuration: CompilerConfiguration,
         outputFiles: OutputFileCollection,
-        mainClassProvider: MainClassProvider?
+        mainClassFqName: FqName?
     ) {
         val reportOutputFiles = configuration.getBoolean(CommonConfigurationKeys.REPORT_OUTPUT_FILES)
         val jarPath = configuration.get(JVMConfigurationKeys.OUTPUT_JAR)
         val messageCollector = configuration.get(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY, MessageCollector.NONE)
         if (jarPath != null) {
             val includeRuntime = configuration.get(JVMConfigurationKeys.INCLUDE_RUNTIME, false)
-            CompileEnvironmentUtil.writeToJar(jarPath, includeRuntime, mainClassProvider?.mainClassFqName, outputFiles)
+            CompileEnvironmentUtil.writeToJar(jarPath, includeRuntime, mainClassFqName, outputFiles)
             if (reportOutputFiles) {
                 val message = OutputMessageUtil.formatOutputMessage(outputFiles.asList().flatMap { it.sourceFiles }.distinct(), jarPath)
                 messageCollector.report(OUTPUT, message)
@@ -200,6 +198,11 @@ object KotlinToJVMBytecodeCompiler {
 
         result.throwIfError()
 
+        val mainClassFqName =
+            if (chunk.size == 1 && projectConfiguration.get(JVMConfigurationKeys.OUTPUT_JAR) != null)
+                findMainClass(result.bindingContext, projectConfiguration.languageVersionSettings, environment.getSourceFiles())
+            else null
+
         val outputs = newLinkedHashMapWithExpectedSize<Module, GenerationState>(chunk.size)
 
         val localFileSystem = VirtualFileManager.getInstance().getFileSystem(StandardFileSystems.FILE_PROTOCOL)
@@ -214,20 +217,20 @@ object KotlinToJVMBytecodeCompiler {
             outputs[module] = generate(environment, moduleConfiguration, result, ktFiles, module)
         }
 
-        return writeOutputs(environment, projectConfiguration, chunk, outputs)
+        return writeOutputs(environment, projectConfiguration, chunk, outputs, mainClassFqName)
     }
 
     private fun writeOutputs(
         environment: KotlinCoreEnvironment,
         projectConfiguration: CompilerConfiguration,
         chunk: List<Module>,
-        outputs: Map<Module, GenerationState>
+        outputs: Map<Module, GenerationState>,
+        mainClassFqName: FqName?
     ): Boolean {
         try {
             for ((_, state) in outputs) {
                 ProgressIndicatorAndCompilationCanceledStatus.checkCanceled()
-                val mainClassProvider = if (outputs.size == 1) MainClassProvider(state, environment) else null
-                writeOutput(state.configuration, state.factory, mainClassProvider)
+                writeOutput(state.configuration, state.factory, mainClassFqName)
             }
         } finally {
             outputs.values.forEach(GenerationState::destroy)
@@ -436,7 +439,13 @@ object KotlinToJVMBytecodeCompiler {
             ProgressIndicatorAndCompilationCanceledStatus.checkCanceled()
             outputs[module] = generationState
         }
-        return writeOutputs(environment, projectConfiguration, chunk, outputs)
+
+        val mainClassFqName: FqName? =
+            if (chunk.size == 1 && projectConfiguration.get(JVMConfigurationKeys.OUTPUT_JAR) != null)
+                TODO(".jar output is not yet supported for -Xuse-fir: KT-42868")
+            else null
+
+        return writeOutputs(environment, projectConfiguration, chunk, outputs, mainClassFqName)
     }
 
     private fun FirDiagnostic<*>.toRegularDiagnostic(): Diagnostic {
@@ -469,22 +478,6 @@ object KotlinToJVMBytecodeCompiler {
             (File(path).takeIf(File::isAbsolute) ?: buildFile.resolveSibling(path)).absolutePath
         }
 
-    class MainClassProvider(generationState: GenerationState, environment: KotlinCoreEnvironment) {
-        val mainClassFqName: FqName? by lazy { findMainClass(generationState, environment.getSourceFiles()) }
-
-        private fun findMainClass(generationState: GenerationState, files: List<KtFile>): FqName? {
-            val mainFunctionDetector = MainFunctionDetector(generationState.bindingContext, generationState.languageVersionSettings)
-            return files.asSequence()
-                .map { file ->
-                    if (mainFunctionDetector.hasMain(file.declarations))
-                        JvmFileClassUtil.getFileClassInfoNoResolve(file).facadeClassFqName
-                    else
-                        null
-                }
-                .singleOrNull { it != null }
-        }
-    }
-
     fun compileBunchOfSources(environment: KotlinCoreEnvironment): Boolean {
         val moduleVisibilityManager = ModuleVisibilityManager.SERVICE.getInstance(environment.project)
 
@@ -498,7 +491,7 @@ object KotlinToJVMBytecodeCompiler {
         val generationState = analyzeAndGenerate(environment) ?: return false
 
         try {
-            writeOutput(environment.configuration, generationState.factory, MainClassProvider(generationState, environment))
+            writeOutput(environment.configuration, generationState.factory, null)
             return true
         } finally {
             generationState.destroy()

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

@@ -5,14 +5,15 @@
 
 package org.jetbrains.kotlin.cli.jvm.compiler
 
-import org.jetbrains.kotlin.codegen.state.GenerationState
+import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 import org.jetbrains.kotlin.idea.MainFunctionDetector
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.resolve.BindingContext
 
-fun findMainClass(generationState: GenerationState, files: List<KtFile>): FqName? {
-    val mainFunctionDetector = MainFunctionDetector(generationState.bindingContext, generationState.languageVersionSettings)
+fun findMainClass(bindingContext: BindingContext, languageVersionSettings: LanguageVersionSettings, files: List<KtFile>): FqName? {
+    val mainFunctionDetector = MainFunctionDetector(bindingContext, languageVersionSettings)
     return files.asSequence()
         .map { file ->
             if (mainFunctionDetector.hasMain(file.declarations))
@@ -21,4 +22,4 @@ fun findMainClass(generationState: GenerationState, files: List<KtFile>): FqName
                 null
         }
         .singleOrNull { it != null }
-}
+}

idea/jvm-debugger/jvm-debugger-test/test/org/jetbrains/kotlin/idea/debugger/test/DebuggerTestCompilerFacility.kt

@@ -10,7 +10,6 @@ import com.intellij.openapi.module.Module
 import com.intellij.openapi.roots.LibraryOrderEntry
 import com.intellij.openapi.roots.ModuleRootManager
 import com.intellij.openapi.roots.OrderRootType
-import com.intellij.openapi.roots.libraries.ui.OrderRoot
 import com.intellij.openapi.util.io.FileUtil
 import com.intellij.openapi.vfs.LocalFileSystem
 import com.intellij.openapi.vfs.VirtualFile
@@ -32,6 +31,7 @@ import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.config.JVMConfigurationKeys
 import org.jetbrains.kotlin.config.JvmTarget
 import org.jetbrains.kotlin.diagnostics.rendering.DefaultErrorMessages
+import org.jetbrains.kotlin.idea.resolve.getLanguageVersionSettings
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.test.KotlinBaseTest.TestFile
 import org.jetbrains.kotlin.test.MockLibraryUtil
@@ -198,7 +198,8 @@ class DebuggerTestCompilerFacility(
 
         state.factory.writeAllTo(classesDir)
 
-        return findMainClass(state, files)?.asString() ?: error("Cannot find main class name")
+        return findMainClass(bindingContext, resolutionFacade.getLanguageVersionSettings(), files)?.asString()
+            ?: error("Cannot find main class name")
     }
 
     private fun getClasspath(module: Module): List<String> {