K2 scripting: treat default import similarly to K1

namely, add them to importing scopes directly and according to the
schema used for other implicit imports, rather than adding them
to the regular script file imports. See KT-65982 for explanation.
#KT-65982 fixed

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/extensions/FirExtensionRegistrar.kt

@@ -33,6 +33,7 @@ abstract class FirExtensionRegistrar : FirExtensionRegistrarAdapter() {
             FirSamConversionTransformerExtension::class,
             FirAssignExpressionAltererExtension::class,
             FirScriptConfiguratorExtension::class,
+            FirScriptResolutionConfigurationExtension::class,
             Fir2IrScriptConfiguratorExtension::class,
             FirFunctionTypeKindExtension::class,
             @OptIn(FirExtensionApiInternals::class)
@@ -100,6 +101,11 @@ abstract class FirExtensionRegistrar : FirExtensionRegistrarAdapter() {
             registerExtension(FirScriptConfiguratorExtension::class, this)
         }
 
+        @JvmName("plusFirScriptResolutionConfigurationExtension")
+        operator fun (FirScriptResolutionConfigurationExtension.Factory).unaryPlus() {
+            registerExtension(FirScriptResolutionConfigurationExtension::class, this)
+        }
+
         @JvmName("plusFir2IrScriptConfiguratorExtension")
         operator fun (Fir2IrScriptConfiguratorExtension.Factory).unaryPlus() {
             registerExtension(Fir2IrScriptConfiguratorExtension::class, this)
@@ -168,6 +174,11 @@ abstract class FirExtensionRegistrar : FirExtensionRegistrarAdapter() {
             FirScriptConfiguratorExtension.Factory { this.invoke(it) }.unaryPlus()
         }
 
+        @JvmName("plusFirScriptResolutionConfigurationExtension")
+        operator fun ((FirSession) -> FirScriptResolutionConfigurationExtension).unaryPlus() {
+            FirScriptResolutionConfigurationExtension.Factory { this.invoke(it) }.unaryPlus()
+        }
+
         @JvmName("plusFir2IrScriptConfiguratorExtension")
         operator fun ((FirSession) -> Fir2IrScriptConfiguratorExtension).unaryPlus() {
             Fir2IrScriptConfiguratorExtension.Factory { this.invoke(it) }.unaryPlus()

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/extensions/FirScriptResolutionConfigurationExtension.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.extensions
+
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.declarations.FirImport
+import org.jetbrains.kotlin.fir.declarations.FirScript
+import kotlin.reflect.KClass
+
+abstract class FirScriptResolutionConfigurationExtension(
+    session: FirSession,
+) : FirExtension(session) {
+    companion object {
+        val NAME = FirExtensionPointName("FirScriptResolutionConfiguration")
+    }
+
+    final override val name: FirExtensionPointName
+        get() = NAME
+
+    final override val extensionType: KClass<out FirExtension> = FirScriptResolutionConfigurationExtension::class
+
+    fun interface Factory : FirExtension.Factory<FirScriptResolutionConfigurationExtension>
+
+    abstract fun getScriptDefaultImports(script: FirScript): List<FirImport>
+}
+
+val FirExtensionService.firScriptResolutionConfigurators: List<FirScriptResolutionConfigurationExtension> by FirExtensionService.registeredExtensions()

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/ImportingScopes.kt

@@ -6,13 +6,15 @@
 package org.jetbrains.kotlin.fir.scopes
 
 import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.declarations.FirFile
-import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.extensions.extensionService
+import org.jetbrains.kotlin.fir.extensions.firScriptResolutionConfigurators
 import org.jetbrains.kotlin.fir.importTracker
 import org.jetbrains.kotlin.fir.packageFqName
 import org.jetbrains.kotlin.fir.reportImportDirectives
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.scopeSessionKey
+import org.jetbrains.kotlin.fir.resolve.transformers.FirImportResolveTransformer
 import org.jetbrains.kotlin.fir.scopes.impl.*
 import org.jetbrains.kotlin.fir.symbols.lazyResolveToPhase
 import org.jetbrains.kotlin.name.FqName
@@ -20,6 +22,8 @@ import org.jetbrains.kotlin.name.FqName
 private val ALL_IMPORTS = scopeSessionKey<FirFile, ListStorageFirScope>()
 private val DEFAULT_STAR_IMPORT = scopeSessionKey<DefaultStarImportKey, FirSingleLevelDefaultStarImportingScope>()
 private val DEFAULT_SIMPLE_IMPORT = scopeSessionKey<DefaultSimpleImportKey, FirDefaultSimpleImportingScope>()
+private val DEFAULT_SCRIPT_STAR_IMPORT = scopeSessionKey<FirFile, FirExplicitStarImportingScope>()
+private val DEFAULT_SCRIPT_SIMPLE_IMPORT = scopeSessionKey<FirFile, FirExplicitSimpleImportingScope>()
 
 private data class DefaultStarImportKey(val priority: DefaultImportPriority, val excludedImportNames: Set<FqName>)
 
@@ -60,6 +64,18 @@ internal fun computeImportingScopes(
         }
     }
 
+    val script = file.declarations.firstOrNull() as? FirScript
+    val scriptDefaultImports by lazy(LazyThreadSafetyMode.NONE) {
+        script?.let {
+            val importResolveTransformer = FirImportResolveTransformer(session)
+            session.extensionService.firScriptResolutionConfigurators.flatMap {
+                it.getScriptDefaultImports(script).map { firImport ->
+                    (importResolveTransformer.transformImport(firImport, null) as? FirResolvedImport) ?: firImport
+                }
+            }
+        }?.partition { it.isAllUnder }
+    }
+
     return buildList {
         if (includeDefaultImports) {
             this += FirDefaultStarImportingScope(
@@ -70,6 +86,11 @@ internal fun computeImportingScopes(
                     FirSingleLevelDefaultStarImportingScope(session, scopeSession, DefaultImportPriority.LOW, excludedImportNames)
                 },
             )
+            if (script != null) {
+                this += scopeSession.getOrBuild(file, DEFAULT_SCRIPT_STAR_IMPORT) {
+                    FirExplicitStarImportingScope(scriptDefaultImports?.first.orEmpty(), session, scopeSession, excludedImportNames)
+                }
+            }
         }
 
         this += FirExplicitStarImportingScope(file.imports, session, scopeSession, excludedImportNames)
@@ -81,6 +102,11 @@ internal fun computeImportingScopes(
             this += scopeSession.getOrBuild(DefaultSimpleImportKey(DefaultImportPriority.HIGH, excludedImportNames), DEFAULT_SIMPLE_IMPORT) {
                 FirDefaultSimpleImportingScope(session, scopeSession, priority = DefaultImportPriority.HIGH, excludedImportNames)
             }
+            if (script != null) {
+                this += scopeSession.getOrBuild(file, DEFAULT_SCRIPT_SIMPLE_IMPORT) {
+                    FirExplicitSimpleImportingScope(scriptDefaultImports?.second.orEmpty(), session, scopeSession)
+                }
+            }
         }
 
         if (includePackageImport) {