Export filename extension from KotlinScriptDefinition, register...

extensions after loading definitions

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/ScriptDefinitionsManager.kt

@@ -41,7 +41,6 @@ import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.script.*
 import org.jetbrains.kotlin.script.util.scriptCompilationClasspathFromContextOrStlib
 import org.jetbrains.kotlin.scripting.compiler.plugin.KotlinScriptDefinitionAdapterFromNewAPI
-import org.jetbrains.kotlin.scripting.compiler.plugin.KotlinScriptDefinitionAdapterFromNewAPIBase
 import org.jetbrains.kotlin.utils.PathUtil
 import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
 import org.jetbrains.kotlin.utils.addToStdlib.flattenTo
@@ -136,18 +135,17 @@ class ScriptDefinitionsManager(private val project: Project) : LazyScriptDefinit
         assert(lock.isWriteLocked) { "updateDefinitions should only be called under the write lock" }
         definitions = definitionsByContributor.values.flattenTo(mutableListOf()).asSequence()
 
-        // Register new file extensions
         val fileTypeManager = FileTypeManager.getInstance()
-        val extensions = definitions?.mapNotNull { definition ->
-            (definition as? KotlinScriptDefinitionAdapterFromNewAPIBase)
-                ?.scriptFileExtensionWithDot?.removePrefix(".")
-                ?.takeIf { fileTypeManager.getFileTypeByExtension(it) != KotlinFileType.INSTANCE }
-        }?.toList()
 
-        if (extensions?.isNotEmpty() == true) {
+        val newExtensions = getKnownFilenameExtensions().filter {
+            fileTypeManager.getFileTypeByExtension(it) != KotlinFileType.INSTANCE
+        }.toList()
+
+        if (newExtensions.any()) {
+            // Register new file extensions
             ApplicationManager.getApplication().invokeLater {
                 runWriteAction {
-                    extensions.forEach {
+                    newExtensions.forEach {
                         fileTypeManager.associateExtension(KotlinFileType.INSTANCE, it)
                     }
                 }