Avoid retaining whole KotlinClassHeader in IDEKotlinBinaryClassCache

Before this change there was a retention chain
VirtualFile -> KotlinBinaryData -> KotlinBinaryHeaderData -> KotlinClassHeader

The latter one contains all binary metadata (a lot of String[])
while only a small part of it is used.

The used parts are moved straight to KotlinBinaryClassHeaderData
in this change.

 #KT-19484 Fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/IDEKotlinBinaryClassCache.kt

@@ -22,14 +22,22 @@ import com.intellij.openapi.util.Key
 import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.openapi.vfs.VirtualFileWithId
 import com.intellij.reference.SoftReference
+import org.jetbrains.kotlin.load.kotlin.JvmMetadataVersion
 import org.jetbrains.kotlin.load.kotlin.KotlinBinaryClassCache
 import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinaryClass
 import org.jetbrains.kotlin.load.kotlin.header.KotlinClassHeader
 import org.jetbrains.kotlin.name.ClassId
 
 object IDEKotlinBinaryClassCache {
-    data class KotlinBinaryHeaderData(val classHeader: KotlinClassHeader, val classId: ClassId)
-    data class KotlinBinaryData(val isKotlinBinary: Boolean, val timestamp: Long, val headerData: KotlinBinaryHeaderData?)
+    class KotlinBinaryClassHeaderData(
+        val classId: ClassId,
+        val kind: KotlinClassHeader.Kind,
+        val metadataVersion: JvmMetadataVersion,
+        val partNamesIfMultifileFacade: List<String>,
+        val packageName: String?
+    )
+
+    data class KotlinBinaryData(val isKotlinBinary: Boolean, val timestamp: Long, val headerData: KotlinBinaryClassHeaderData?)
 
     /**
      * Checks if this file is a compiled Kotlin class file (not necessarily ABI-compatible with the current plugin)
@@ -67,7 +75,7 @@ object IDEKotlinBinaryClassCache {
         return kotlinBinaryClass
     }
 
-    fun getKotlinBinaryClassHeaderData(file: VirtualFile, fileContent: ByteArray? = null): KotlinBinaryHeaderData? {
+    fun getKotlinBinaryClassHeaderData(file: VirtualFile, fileContent: ByteArray? = null): KotlinBinaryClassHeaderData? {
         val cached = getKotlinBinaryFromCache(file)
         if (cached != null) {
             if (!cached.isKotlinBinary) {
@@ -84,13 +92,17 @@ object IDEKotlinBinaryClassCache {
 
     private val attributeService = ServiceManager.getService(FileAttributeService::class.java)
 
-    private fun createHeaderInfo(kotlinBinaryClass: KotlinJvmBinaryClass?): KotlinBinaryHeaderData? {
-        val header = kotlinBinaryClass?.classHeader
-        val classId = kotlinBinaryClass?.classId
+    private fun createHeaderInfo(kotlinBinaryClass: KotlinJvmBinaryClass?): KotlinBinaryClassHeaderData? {
+        val classId = kotlinBinaryClass?.classId ?: return null
 
-        return if (header != null && classId != null) KotlinBinaryHeaderData(header, classId) else null
+        return kotlinBinaryClass.classHeader.toLightHeader(classId)
     }
 
+    private fun KotlinClassHeader.toLightHeader(classId: ClassId) =
+        KotlinBinaryClassHeaderData(
+            classId, kind, metadataVersion, multifilePartNames, packageName
+        )
+
     private val KOTLIN_IS_COMPILED_FILE_ATTRIBUTE: String = "kotlin-is-binary-compiled".apply {
         ServiceManager.getService(FileAttributeService::class.java)?.register(this, 1)
     }
@@ -120,4 +132,4 @@ object IDEKotlinBinaryClassCache {
 
         return null
     }
-}
+}

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/ClassFileDecompilerUtil.kt

@@ -42,7 +42,7 @@ fun isKotlinWithCompatibleAbiVersion(file: VirtualFile): Boolean {
     if (!IDEKotlinBinaryClassCache.isKotlinJvmCompiledFile(file)) return false
 
     val kotlinClass = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(file)
-    return kotlinClass != null && kotlinClass.classHeader.metadataVersion.isCompatible()
+    return kotlinClass != null && kotlinClass.metadataVersion.isCompatible()
 }
 
 /**
@@ -69,18 +69,18 @@ fun isKotlinInternalCompiledFile(file: VirtualFile, fileContent: ByteArray? = nu
         return true
     }
 
-    val (header, classId) = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(file, fileContent) ?: return false
-    if (classId.isLocal) return true
+    val header = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(file, fileContent) ?: return false
+    if (header.classId.isLocal) return true
 
     return header.kind == KotlinClassHeader.Kind.SYNTHETIC_CLASS ||
            header.kind == KotlinClassHeader.Kind.MULTIFILE_CLASS_PART
 }
 
-fun findMultifileClassParts(file: VirtualFile, classId: ClassId, header: KotlinClassHeader): List<KotlinJvmBinaryClass> {
+fun findMultifileClassParts(file: VirtualFile, classId: ClassId, partNames: List<String>): List<KotlinJvmBinaryClass> {
     val packageFqName = classId.packageFqName
     val partsFinder = DirectoryBasedClassFinder(file.parent!!, packageFqName)
-    val partNames = header.data ?: return emptyList()
+
     return partNames.mapNotNull {
         partsFinder.findKotlinClass(ClassId(packageFqName, Name.identifier(it.substringAfterLast('/'))))
     }
-}
+}

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/KotlinClassFileDecompiler.kt

@@ -67,9 +67,11 @@ fun buildDecompiledTextForClassFile(
         classFile: VirtualFile,
         resolver: ResolverForDecompiler = DeserializerForClassfileDecompiler(classFile)
 ): DecompiledText {
-    val (classHeader, classId) = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(classFile)
+    val classHeader = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(classFile)
                                  ?: error("Decompiled data factory shouldn't be called on an unsupported file: " + classFile)
 
+    val classId = classHeader.classId
+
     if (!classHeader.metadataVersion.isCompatible()) {
         return createIncompatibleAbiVersionDecompiledText(JvmMetadataVersion.INSTANCE, classHeader.metadataVersion)
     }
@@ -85,7 +87,7 @@ fun buildDecompiledTextForClassFile(
             buildText(listOfNotNull(resolver.resolveTopLevelClass(classId)))
         }
         KotlinClassHeader.Kind.MULTIFILE_CLASS -> {
-            val partClasses = findMultifileClassParts(classFile, classId, classHeader)
+            val partClasses = findMultifileClassParts(classFile, classId, classHeader.partNamesIfMultifileFacade)
             val partMembers = partClasses.flatMap { partClass ->
                 resolver.resolveDeclarationsInFacade(partClass.classId.asSingleFqName())
             }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/KotlinClsStubBuilder.kt

@@ -64,7 +64,7 @@ open class KotlinClsStubBuilder : ClsStubBuilder() {
 
         val components = createStubBuilderComponents(file, packageFqName, fileContent)
         if (header.kind == KotlinClassHeader.Kind.MULTIFILE_CLASS) {
-            val partFiles = findMultifileClassParts(file, classId, header)
+            val partFiles = findMultifileClassParts(file, classId, header.multifilePartNames)
             return createMultifileClassStub(header, partFiles, classId.asSingleFqName(), components)
         }
 

idea/idea-analysis/src/org/jetbrains/kotlin/idea/vfilefinder/fileIndexes.kt

@@ -93,7 +93,7 @@ object KotlinClassFileIndex : KotlinFileIndexBase<KotlinClassFileIndex>(KotlinCl
 
     private val INDEXER = indexer { fileContent ->
         val headerInfo = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(fileContent.file, fileContent.content)
-        if (headerInfo != null && headerInfo.classHeader.metadataVersion.isCompatible()) headerInfo.classId.asSingleFqName() else null
+        if (headerInfo != null && headerInfo.metadataVersion.isCompatible()) headerInfo.classId.asSingleFqName() else null
     }
 }
 

idea/tests/org/jetbrains/kotlin/idea/decompiler/AbstractInternalCompiledClassesTest.kt

@@ -26,9 +26,9 @@ import org.jetbrains.kotlin.name.ClassId
 import org.junit.Assert
 
 abstract class AbstractInternalCompiledClassesTest : KotlinLightCodeInsightFixtureTestCase() {
-    private fun isFileWithHeader(predicate: (KotlinClassHeader, ClassId) -> Boolean) : VirtualFile.() -> Boolean = {
+    private fun isFileWithHeader(predicate: (IDEKotlinBinaryClassCache.KotlinBinaryClassHeaderData, ClassId) -> Boolean) : VirtualFile.() -> Boolean = {
         val info = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(this)
-        info != null && predicate(info.classHeader, info.classId)
+        info != null && predicate(info, info.classId)
     }
 
     protected fun isSyntheticClass(): VirtualFile.() -> Boolean =