Always scan root for script templates in background

^KT-29893 Fixed

Provide AsyncScriptDefinitionsContributor.
Show a notification if the highlighting for script is requested when not all script templates are loaded

idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinHighlightingUtil.kt

@@ -20,6 +20,7 @@ import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.idea.caches.project.NotUnderContentRootModuleInfo
 import org.jetbrains.kotlin.idea.caches.project.getModuleInfo
 import org.jetbrains.kotlin.idea.core.script.IdeScriptReportSink
+import org.jetbrains.kotlin.idea.core.script.ScriptDefinitionsManager
 import org.jetbrains.kotlin.idea.core.script.scriptDependencies
 import org.jetbrains.kotlin.idea.util.ProjectRootsUtil
 import org.jetbrains.kotlin.psi.KtCodeFragment
@@ -69,6 +70,8 @@ object KotlinHighlightingUtil {
             return false
         }
 
+        if (!ScriptDefinitionsManager.getInstance(ktFile.project).isReady()) return false
+
         return ProjectRootsUtil.isInProjectSource(ktFile, includeScriptsOutsideSourceRoots = true)
     }
 }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/ScriptExternalHighlightingPass.kt

@@ -31,8 +31,13 @@ import com.intellij.openapi.editor.Document
 import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.progress.ProgressIndicator
 import com.intellij.openapi.project.DumbAware
+import com.intellij.openapi.ui.MessageType
+import com.intellij.openapi.wm.WindowManager
+import com.intellij.openapi.wm.ex.StatusBarEx
 import com.intellij.psi.PsiFile
+import com.intellij.util.ui.UIUtil
 import org.jetbrains.kotlin.idea.core.script.IdeScriptReportSink
+import org.jetbrains.kotlin.idea.core.script.ScriptDefinitionsManager
 import org.jetbrains.kotlin.psi.KtFile
 import kotlin.script.experimental.dependencies.ScriptReport
 
@@ -45,6 +50,23 @@ class ScriptExternalHighlightingPass(
     override fun doApplyInformationToEditor() {
         val document = document ?: return
 
+        if (!file.isScript()) return
+
+        if (!ScriptDefinitionsManager.getInstance(file.project).isReady()) {
+            UIUtil.invokeLaterIfNeeded {
+                val ideFrame = WindowManager.getInstance().getIdeFrame(file.project)
+                if (ideFrame != null) {
+                    val statusBar = ideFrame.statusBar as StatusBarEx
+                    statusBar.notifyProgressByBalloon(
+                        MessageType.WARNING,
+                        "Highlighting in scripts is not available until all Script Definitions are loaded",
+                        null,
+                        null
+                    )
+                }
+            }
+        }
+
         val reports = file.virtualFile.getUserData(IdeScriptReportSink.Reports) ?: return
 
         val annotations = reports.mapNotNull { (message, severity, position) ->