IDE scripting: add default sdk only when used

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/configuration/utils/ScriptClassRootsStorage.kt

@@ -22,6 +22,7 @@ class ScriptClassRootsStorage(val project: Project) : PersistentStateComponent<S
     var classpath: Set<String> = hashSetOf()
     var sources: Set<String> = hashSetOf()
     var sdks: Set<String> = hashSetOf()
+    var defaultSdkUsed: Boolean = false
 
     override fun getState(): ScriptClassRootsStorage? {
         return this

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/uсache/ScriptClassRootsBuilder.kt

@@ -77,10 +77,8 @@ class ScriptClassRootsBuilder(
             storage.project,
             storage.classpath.toMutableSet(),
             storage.sources.toMutableSet(),
-        ).also { roots ->
-            storage.sdks.forEach {
-                roots.sdks.addSdkByName(it)
-            }
+        ).also {
+            it.sdks.fromStorage(storage)
         }
     }
 }

idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/uсache/ScriptSdksBuilder.kt

@@ -22,11 +22,7 @@ class ScriptSdksBuilder(
     private val sdks: MutableMap<String?, Sdk?> = mutableMapOf(),
     private val remove: Sdk? = null
 ) {
-    private val defaultSdk = getScriptDefaultSdk()
-
-    init {
-        sdks[null] = defaultSdk
-    }
+    private val defaultSdk by lazy { getScriptDefaultSdk() }
 
     fun build() = ScriptSdks(project, sdks)
 
@@ -35,7 +31,8 @@ class ScriptSdksBuilder(
     }
 
     fun addSdk(javaHome: File?): Sdk? {
-        if (javaHome == null) return defaultSdk
+        if (javaHome == null) return addDefaultSdk()
+
         val canonicalPath = FileUtil.toSystemIndependentName(javaHome.canonicalPath)
         return sdks.getOrPut(canonicalPath) {
             getScriptSdkByJavaHome(javaHome) ?: defaultSdk
@@ -54,6 +51,9 @@ class ScriptSdksBuilder(
             ?.takeIf { it.canBeUsedForScript() }
     }
 
+    fun addDefaultSdk(): Sdk? =
+        sdks.getOrPut(null) { defaultSdk }
+
     fun addSdkByName(sdkName: String) {
         val sdk = getProjectJdkTableSafe().allJdks
             .find { it.name == sdkName }
@@ -85,5 +85,15 @@ class ScriptSdksBuilder(
 
     fun toStorage(storage: ScriptClassRootsStorage) {
         storage.sdks = sdks.values.mapNotNullTo(mutableSetOf()) { it?.name }
+        storage.defaultSdkUsed = sdks.containsKey(null)
+    }
+
+    fun fromStorage(storage: ScriptClassRootsStorage) {
+        storage.sdks.forEach {
+            addSdkByName(it)
+        }
+        if (storage.defaultSdkUsed) {
+            addDefaultSdk()
+        }
     }
 }