[KLIB tool] Refactoring. Fix visibility, add comments, drop useless code

What's done:
- Reduce the visibility of all entities inside the module to `internal`
  or `private`. Only leave `fun main()` as `public` because it's the
  single legal entry point.
- Add comments to few classes related to "contents" command that they
  should be removed together with the command after 2.0.
- Drop useless `DeclarationHeaderRenderer` interface.
- Rename: KlibToolLinker -> KlibToolIrLinker

^KT-62340

kotlin-native/klib/src/main/kotlin/org/jetbrains/kotlin/cli/klib/DeclarationHeaderRenderer.kt

@@ -1,7 +0,0 @@
-package org.jetbrains.kotlin.cli.klib
-
-import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
-
-interface DeclarationHeaderRenderer {
-    fun render(descriptor: DeclarationDescriptor): String
-}

kotlin-native/klib/src/main/kotlin/org/jetbrains/kotlin/cli/klib/DeclarationPrinter.kt

@@ -7,9 +7,9 @@ import org.jetbrains.kotlin.descriptors.DescriptorVisibilities.INTERNAL
 import org.jetbrains.kotlin.descriptors.impl.DeclarationDescriptorVisitorEmptyBodies
 import org.jetbrains.kotlin.utils.Printer
 
+// TODO: This class is used in dumping metadata by descriptors, "contents" command. Drop it after 2.0. KT-65380
 internal class DeclarationPrinter(
         out: Appendable,
-        private val headerRenderer: DeclarationHeaderRenderer,
         private val signatureRenderer: KlibSignatureRenderer
 ) {
     private val printer = Printer(out, 1, "    ")
@@ -53,14 +53,14 @@ internal class DeclarationPrinter(
                 .filter { it.shouldBePrinted }
                 .sortedBy { it.name }
             if (children.isNotEmpty()) {
-                printer.printWithBody(header = headerRenderer.render(descriptor)) {
+                printer.printWithBody(header = DefaultDeclarationHeaderRenderer.render(descriptor)) {
                     children.forEach { it.accept(this, data) }
                 }
             }
         }
 
         override fun visitClassDescriptor(descriptor: ClassDescriptor, data: Unit) {
-            val header = headerRenderer.render(descriptor)
+            val header = DefaultDeclarationHeaderRenderer.render(descriptor)
             val signature = signatureRenderer.render(descriptor)
 
             val children = descriptor.unsubstitutedMemberScope.getContributedDescriptors().filter { it.shouldBePrinted }
@@ -76,19 +76,19 @@ internal class DeclarationPrinter(
         }
 
         override fun visitFunctionDescriptor(descriptor: FunctionDescriptor, data: Unit) {
-            printer.printPlain(header = headerRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
+            printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
         }
 
         override fun visitPropertyDescriptor(descriptor: PropertyDescriptor, data: Unit) {
-            printer.printPlain(header = headerRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
+            printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
             descriptor.getter?.takeUnless { canSkipAccessor(it, descriptor) }?.let { getter ->
                 printer.pushIndent()
-                printer.printPlain(header = headerRenderer.render(getter), signature = signatureRenderer.render(getter))
+                printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(getter), signature = signatureRenderer.render(getter))
                 printer.popIndent()
             }
             descriptor.setter?.takeUnless { canSkipAccessor(it, descriptor) }?.let { setter ->
                 printer.pushIndent()
-                printer.printPlain(header = headerRenderer.render(setter), signature = signatureRenderer.render(setter))
+                printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(setter), signature = signatureRenderer.render(setter))
                 printer.popIndent()
             }
         }
@@ -98,11 +98,11 @@ internal class DeclarationPrinter(
         }
 
         override fun visitConstructorDescriptor(descriptor: ConstructorDescriptor, data: Unit) {
-            printer.printPlain(header = headerRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
+            printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
         }
 
         override fun visitTypeAliasDescriptor(descriptor: TypeAliasDescriptor, data: Unit) {
-            printer.printPlain(header = headerRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
+            printer.printPlain(header = DefaultDeclarationHeaderRenderer.render(descriptor), signature = signatureRenderer.render(descriptor))
         }
     }
 }

kotlin-native/klib/src/main/kotlin/org/jetbrains/kotlin/cli/klib/DefaultDeclarationHeaderRenderer.kt

@@ -7,8 +7,9 @@ import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.renderer.DescriptorRendererModifier
 import org.jetbrains.kotlin.renderer.OverrideRenderingPolicy
 
-object DefaultDeclarationHeaderRenderer : DeclarationHeaderRenderer {
-    override fun render(descriptor: DeclarationDescriptor): String = when (descriptor) {
+// TODO: This class is used in dumping metadata by descriptors, "contents" command. Drop it after 2.0. KT-65380
+internal object DefaultDeclarationHeaderRenderer {
+    fun render(descriptor: DeclarationDescriptor): String = when (descriptor) {
         is PackageFragmentDescriptor -> render(descriptor)
         is ClassifierDescriptorWithTypeParameters -> render(descriptor)
         is PropertyAccessorDescriptor -> render(descriptor)

kotlin-native/klib/src/main/kotlin/org/jetbrains/kotlin/cli/klib/main.kt

@@ -18,7 +18,6 @@ import org.jetbrains.kotlin.backend.konan.serialization.KonanManglerIr
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
-import org.jetbrains.kotlin.ir.builders.TranslationPluginContext
 import org.jetbrains.kotlin.ir.declarations.impl.IrFactoryImpl
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl
 import org.jetbrains.kotlin.ir.util.DumpIrTreeOptions
@@ -40,7 +39,7 @@ import java.io.File
 import kotlin.system.exitProcess
 import org.jetbrains.kotlin.konan.file.File as KFile
 
-fun printUsage() {
+private fun printUsage() {
     println(
             """
             Usage: klib <command> <library> [<option>]
@@ -98,7 +97,7 @@ private fun parseOptions(args: Array<String>): Map<String, List<String>> {
 }
 
 
-private class Command(args: Array<String>) {
+internal class Command(args: Array<String>) {
     init {
         if (args.size < 2) {
             printUsage()
@@ -132,20 +131,7 @@ private fun Command.parseSignatureVersion(): KotlinIrSignatureVersion? {
     return signatureVersion
 }
 
-internal fun logWarning(text: String) {
-    println("warning: $text")
-}
-
-internal fun logError(text: String, withStacktrace: Boolean = false): Nothing {
-    if (withStacktrace)
-        error("error: $text")
-    else {
-        System.err.println("error: $text")
-        exitProcess(1)
-    }
-}
-
-object KlibToolLogger : Logger, IrMessageLogger {
+internal object KlibToolLogger : Logger, IrMessageLogger {
     override fun log(message: String) = println(message)
     override fun warning(message: String) = logWarning(message)
     override fun error(message: String) = logWarning(message)
@@ -162,7 +148,20 @@ object KlibToolLogger : Logger, IrMessageLogger {
     }
 }
 
-val defaultRepository = KFile(DependencyDirectories.localKonanDir.resolve("klib").absolutePath)
+internal fun logWarning(text: String) {
+    println("warning: $text")
+}
+
+internal fun logError(text: String, withStacktrace: Boolean = false): Nothing {
+    if (withStacktrace)
+        error("error: $text")
+    else {
+        System.err.println("error: $text")
+        exitProcess(1)
+    }
+}
+
+private val defaultRepository = KFile(DependencyDirectories.localKonanDir.resolve("klib").absolutePath)
 
 private class KlibRepoDeprecationWarning {
     private var alreadyLogged = false
@@ -175,11 +174,11 @@ private class KlibRepoDeprecationWarning {
     }
 }
 
-class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
+internal class Library(val libraryNameOrPath: String, requestedRepository: String?) {
 
     private val klibRepoDeprecationWarning = KlibRepoDeprecationWarning()
 
-    val repository = requestedRepository?.let {
+    private val repository = requestedRepository?.let {
         klibRepoDeprecationWarning.logOnceIfNecessary() // Due to use of "-repository" option.
         KFile(it)
     } ?: defaultRepository
@@ -242,9 +241,11 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
         library?.libraryFile?.deleteRecursively()
     }
 
-    class KlibToolLinker(
-            module: ModuleDescriptor, irBuiltIns: IrBuiltIns, symbolTable: SymbolTable
-    ) : KotlinIrLinker(module, KlibToolLogger, irBuiltIns, symbolTable, emptyList()) {
+    class KlibToolIrLinker(
+            module: ModuleDescriptor,
+            irBuiltIns: IrBuiltIns,
+            symbolTable: SymbolTable
+    ) : KotlinIrLinker(module, KlibToolLogger, irBuiltIns, symbolTable, exportedDependencies = emptyList()) {
         override val fakeOverrideBuilder = IrLinkerFakeOverrideProvider(
                 linker = this,
                 symbolTable = symbolTable,
@@ -254,25 +255,23 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
                 partialLinkageSupport = PartialLinkageSupportForLinker.DISABLED,
         )
 
-        override val returnUnboundSymbolsIfSignatureNotFound: Boolean
-            get() = true
+        override val returnUnboundSymbolsIfSignatureNotFound get() = true
 
-        override val translationPluginContext: TranslationPluginContext
-            get() = TODO("Not needed for ir dumping")
+        override val translationPluginContext get() = TODO("Not needed for ir dumping")
 
-        override fun createModuleDeserializer(moduleDescriptor: ModuleDescriptor, klib: KotlinLibrary?, strategyResolver: (String) -> DeserializationStrategy): IrModuleDeserializer {
-            return KlibToolModuleDeserializer(
-                    module = moduleDescriptor,
-                    klib = klib ?: error("Expecting kotlin library for $moduleDescriptor"),
-                    strategyResolver = strategyResolver
-            )
-        }
+        override fun createModuleDeserializer(
+                moduleDescriptor: ModuleDescriptor,
+                klib: KotlinLibrary?,
+                strategyResolver: (String) -> DeserializationStrategy
+        ): IrModuleDeserializer = KlibToolModuleDeserializer(
+                module = moduleDescriptor,
+                klib = klib ?: error("Expecting kotlin library for $moduleDescriptor"),
+                strategyResolver = strategyResolver
+        )
 
-        override fun isBuiltInModule(moduleDescriptor: ModuleDescriptor): Boolean {
-            return false
-        }
+        override fun isBuiltInModule(moduleDescriptor: ModuleDescriptor) = false
 
-        inner class KlibToolModuleDeserializer(
+        private inner class KlibToolModuleDeserializer(
                 module: ModuleDescriptor,
                 klib: KotlinLibrary,
                 strategyResolver: (String) -> DeserializationStrategy
@@ -302,7 +301,7 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
         val typeTranslator = TypeTranslatorImpl(symbolTable, ModuleDescriptorLoader.languageVersionSettings, module)
         val irBuiltIns = IrBuiltInsOverDescriptors(module.builtIns, typeTranslator, symbolTable)
 
-        val linker = KlibToolLinker(module, irBuiltIns, symbolTable)
+        val linker = KlibToolIrLinker(module, irBuiltIns, symbolTable)
         module.allDependencyModules.forEach {
             linker.deserializeOnlyHeaderModule(it, it.kotlinLibrary)
             linker.resolveModuleDeserializer(it, null).init()
@@ -363,6 +362,7 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
         )
     }
 
+    // TODO: This command is deprecated. Drop it after 2.0. KT-65380
     fun contents(output: Appendable, printSignatures: Boolean, signatureVersion: KotlinIrSignatureVersion?) {
         logWarning("\"contents\" has been renamed to \"dump-metadata\". Please, use new command name.")
         val module = ModuleDescriptorLoader.load(libraryInRepoOrCurrentDir(repository, libraryNameOrPath))
@@ -370,7 +370,7 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
             DefaultKlibSignatureRenderer(signatureVersion, "// Signature: ")
         else
             KlibSignatureRenderer.NO_SIGNATURE
-        val printer = DeclarationPrinter(output, DefaultDeclarationHeaderRenderer, signatureRenderer)
+        val printer = DeclarationPrinter(output, signatureRenderer)
 
         printer.print(module)
     }
@@ -419,12 +419,12 @@ class Library(val libraryNameOrPath: String, val requestedRepository: String?) {
     }
 }
 
-fun libraryInRepo(repository: KFile, name: String) =
+private fun libraryInRepo(repository: KFile, name: String) =
         resolverByName(listOf(repository.absolutePath), skipCurrentDir = true, logger = KlibToolLogger).resolve(name)
 
-fun libraryInCurrentDir(name: String) = resolverByName(emptyList(), logger = KlibToolLogger).resolve(name)
+private fun libraryInCurrentDir(name: String) = resolverByName(emptyList(), logger = KlibToolLogger).resolve(name)
 
-fun libraryInRepoOrCurrentDir(repository: KFile, name: String) =
+private fun libraryInRepoOrCurrentDir(repository: KFile, name: String) =
         resolverByName(listOf(repository.absolutePath), logger = KlibToolLogger).resolve(name)
 
 private enum class KnownOption(val option: String) {