K2: add a check for duplicate source root

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

@@ -52,7 +52,6 @@ import org.jetbrains.kotlin.cli.common.CliModuleVisibilityManagerImpl
 import org.jetbrains.kotlin.cli.common.CompilerSystemProperties
 import org.jetbrains.kotlin.cli.common.config.ContentRoot
 import org.jetbrains.kotlin.cli.common.config.KotlinSourceRoot
-import org.jetbrains.kotlin.cli.common.config.kotlinSourceRoots
 import org.jetbrains.kotlin.cli.common.environment.setIdeaIoUseFallback
 import org.jetbrains.kotlin.cli.common.extensions.ScriptEvaluationExtension
 import org.jetbrains.kotlin.cli.common.extensions.ShellExtension
@@ -195,7 +194,10 @@ class KotlinCoreEnvironment private constructor(
         val project = projectEnvironment.project
         project.registerService(DeclarationProviderFactoryService::class.java, CliDeclarationProviderFactoryService(sourceFiles))
 
-        sourceFiles += createSourceFilesFromSourceRoots(configuration, project, getSourceRootsCheckingForDuplicates())
+        sourceFiles += createSourceFilesFromSourceRoots(
+            configuration, project,
+            getSourceRootsCheckingForDuplicates(configuration, configuration[CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY])
+        )
 
         collectAdditionalSources(project)
 
@@ -402,20 +404,6 @@ class KotlinCoreEnvironment private constructor(
     private fun findJarRoot(file: File): VirtualFile? =
         projectEnvironment.jarFileSystem.findFileByPath("$file${URLUtil.JAR_SEPARATOR}")
 
-    private fun getSourceRootsCheckingForDuplicates(): List<KotlinSourceRoot> {
-        val uniqueSourceRoots = hashSetOf<String>()
-        val result = mutableListOf<KotlinSourceRoot>()
-
-        for (root in configuration.kotlinSourceRoots) {
-            if (!uniqueSourceRoots.add(root.path)) {
-                report(STRONG_WARNING, "Duplicate source root: ${root.path}")
-            }
-            result.add(root)
-        }
-
-        return result
-    }
-
     fun getSourceFiles(): List<KtFile> =
         ProcessSourcesBeforeCompilingExtension.getInstances(project)
             .fold(sourceFiles as Collection<KtFile>) { files, extension ->

compiler/cli/cli-base/src/org/jetbrains/kotlin/cli/jvm/compiler/coreEnvironmentUtils.kt

@@ -15,6 +15,7 @@ import com.intellij.openapi.vfs.VirtualFileManager
 import com.intellij.psi.PsiManager
 import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys
 import org.jetbrains.kotlin.cli.common.config.KotlinSourceRoot
+import org.jetbrains.kotlin.cli.common.config.kotlinSourceRoots
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageLocation
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity
 import org.jetbrains.kotlin.cli.common.messages.MessageCollector
@@ -143,3 +144,18 @@ fun CompilerConfiguration.applyModuleProperties(module: Module, buildFile: File?
     }
 }
 
+fun getSourceRootsCheckingForDuplicates(configuration: CompilerConfiguration, messageCollector: MessageCollector?): List<KotlinSourceRoot> {
+    val uniqueSourceRoots = hashSetOf<String>()
+    val result = mutableListOf<KotlinSourceRoot>()
+
+    for (root in configuration.kotlinSourceRoots) {
+        if (!uniqueSourceRoots.add(root.path)) {
+            messageCollector?.report(CompilerMessageSeverity.STRONG_WARNING, "Duplicate source root: ${root.path}")
+        }
+        result.add(root)
+    }
+
+    return result
+}
+
+