Fixes after review

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

@@ -58,6 +58,20 @@ interface JvmDependenciesIndex {
     ): Set<String>
 }
 
+interface JvmDependenciesIndexFactory {
+    fun makeIndexFor(roots: List<JavaRoot>): JvmDependenciesIndex
+}
+
+class JvmStaticDependenciesIndexFactory : JvmDependenciesIndexFactory {
+    override fun makeIndexFor(roots: List<JavaRoot>): JvmDependenciesIndex = JvmDependenciesIndexImpl(roots)
+}
+
+class JvmUpdatableDependenciesIndexFactory : JvmDependenciesIndexFactory {
+    override fun makeIndexFor(roots: List<JavaRoot>): JvmDependenciesIndex = JvmDependenciesDynamicCompoundIndex().apply {
+        addIndex(JvmDependenciesIndexImpl(roots))
+    }
+}
+
 // speeds up finding files/classes in classpath/java source roots
 // NOT THREADSAFE, needs to be adapted/removed if we want compiler to be multithreaded
 // the main idea of this class is for each package to store roots which contains it to avoid excessive file system traversal
@@ -355,9 +369,10 @@ class JvmDependenciesDynamicCompoundIndex() : JvmDependenciesIndex {
     }
 
     override fun collectKnownClassNamesInPackage(packageFqName: FqName): Set<String> = lock.read {
-        indices.fold(hashSetOf(), { s, index -> s.addAll(index.collectKnownClassNamesInPackage(packageFqName)); s })
+        indices.flatMapTo(hashSetOf()) { it.collectKnownClassNamesInPackage(packageFqName) }
     }
 }
 
 private fun IntArrayList.lastOrNull() = if (isEmpty) null else get(size() - 1)
-private val IntArrayList.indices: IntRange get() = 0..(size() - 1)
+private val IntArrayList.indices: IntRange get() = 0..(size() - 1)
+

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

@@ -154,15 +154,15 @@ class KotlinCoreEnvironment private constructor(
         }
 
         val initialRoots = configuration.getList(JVMConfigurationKeys.CONTENT_ROOTS).classpathRoots()
-        val initialIndex = JvmDependenciesIndexImpl(initialRoots)
-        updateClasspathFromRootsIndex(initialIndex)
 
-        // replacing index with updatable one only for REPL mode, so we can add roots to classpath then compiling
-        // subsequent lines in REPL
-        rootsIndex = if (!configuration.getBoolean(CommonConfigurationKeys.REPL_MODE)) initialIndex
-                     else JvmDependenciesDynamicCompoundIndex().apply {
-                         addIndex(initialIndex)
-                     }
+        // TODO: pass index factory in the configuration to avoid selection logic here
+        // for a moment using updatable index for REPL mode, so we can add roots to classpath then compiling subsequent lines in REPL
+        val indexFactory = if (configuration.getBoolean(CommonConfigurationKeys.REPL_MODE)) JvmUpdatableDependenciesIndexFactory()
+                           else JvmStaticDependenciesIndexFactory()
+
+        rootsIndex = indexFactory.makeIndexFor(initialRoots)
+        updateClasspathFromRootsIndex(rootsIndex)
+
         (ServiceManager.getService(project, CoreJavaFileManager::class.java)
             as KotlinCliJavaFileManagerImpl).initIndex(rootsIndex)