Try to approximate "build.gradle.kts" script dependencies on first access

This is a hacky solution to prevent whole file being highlighted as unresolved while we wait for gradle response

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

@@ -58,6 +58,8 @@ class ScriptDependenciesCache(private val project: Project) {
         NonClasspathDirectoriesScope(allLibrarySources)
     }
 
+    fun <T> inspectCache(body: (Map<String, ScriptDependencies>) -> T): T = cacheLock.read { body(cache) }
+
     private fun onChange(file: VirtualFile?) {
         this::allScriptsClasspath.clearValue()
         this::allScriptsClasspathScope.clearValue()

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

@@ -51,7 +51,7 @@ class ScriptDependenciesManager internal constructor(
     }
 
     fun getScriptClasspath(file: VirtualFile): List<VirtualFile> = toVfsRoots(cacheUpdater.getCurrentDependencies(file).classpath)
-    fun getScriptDependencies(file: VirtualFile) = cacheUpdater.getCurrentDependencies(file)
+    fun getScriptDependencies(file: VirtualFile): ScriptDependencies = cacheUpdater.getCurrentDependencies(file)
 
     private fun reloadScriptDefinitions() {
         val def = makeScriptDefsFromTemplatesProviderExtensions(

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

@@ -18,7 +18,6 @@ package org.jetbrains.kotlin.idea.core.script
 
 import com.intellij.openapi.application.Application
 import com.intellij.openapi.application.ApplicationManager
-import com.intellij.openapi.application.ModalityState
 import com.intellij.openapi.components.ServiceManager
 import com.intellij.openapi.project.Project
 import com.intellij.openapi.project.isProjectOrWorkspaceFile
@@ -35,11 +34,13 @@ import kotlinx.coroutines.experimental.Job
 import kotlinx.coroutines.experimental.asCoroutineDispatcher
 import kotlinx.coroutines.experimental.launch
 import org.jetbrains.annotations.TestOnly
+import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
 import org.jetbrains.kotlin.idea.core.util.EDT
 import org.jetbrains.kotlin.idea.core.util.cancelOnDisposal
 import org.jetbrains.kotlin.idea.util.application.runWriteAction
 import org.jetbrains.kotlin.psi.NotNullableUserDataProperty
 import org.jetbrains.kotlin.script.*
+import org.jetbrains.kotlin.utils.addToStdlib.firstNotNullResult
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.Executors
 import kotlin.script.experimental.dependencies.AsyncDependenciesResolver
@@ -77,20 +78,33 @@ internal class ScriptDependenciesUpdater(
     fun getCurrentDependencies(file: VirtualFile): ScriptDependencies {
         cache[file]?.let { return it }
 
-        tryLoadingFromDisk(file)
+        val loaded = tryLoadingFromDisk(file)
+
+        if (!loaded) {
+            tryUsingDefault(file)
+        }
 
         updateCache(listOf(file))
 
         return cache[file] ?: ScriptDependencies.Empty
     }
 
-    private fun tryLoadingFromDisk(file: VirtualFile) {
-        ScriptDependenciesFileAttribute.read(file)?.let { deserialized ->
-            val rootsChanged = cache.hasNotCachedRoots(deserialized)
-            cache.save(file, deserialized)
-            if (rootsChanged) {
-                notifyRootsChanged()
-            }
+    private fun tryUsingDefault(file: VirtualFile) {
+        val defaults = DefaultScriptDependenciesProvider.getInstances(project).firstNotNullResult { it.defaultDependenciesFor(file) } ?: return
+        saveToCache(defaults, file)
+    }
+
+    private fun tryLoadingFromDisk(file: VirtualFile): Boolean {
+        val deserializedDependencies = ScriptDependenciesFileAttribute.read(file) ?: return false
+        saveToCache(deserializedDependencies, file)
+        return true
+    }
+
+    private fun saveToCache(deserialized: ScriptDependencies, file: VirtualFile) {
+        val rootsChanged = cache.hasNotCachedRoots(deserialized)
+        cache.save(file, deserialized)
+        if (rootsChanged) {
+            notifyRootsChanged()
         }
     }
 
@@ -280,4 +294,14 @@ private object TimeStamps {
 }
 
 @set: TestOnly
-var Application.isScriptDependenciesUpdaterDisabled by NotNullableUserDataProperty(Key.create("SCRIPT_DEPENDENCIES_UPDATER_DISABLED"), false)
+var Application.isScriptDependenciesUpdaterDisabled by NotNullableUserDataProperty(Key.create("SCRIPT_DEPENDENCIES_UPDATER_DISABLED"), false)
+
+interface DefaultScriptDependenciesProvider {
+    fun defaultDependenciesFor(scriptFile: VirtualFile): ScriptDependencies?
+
+    companion object : ProjectExtensionDescriptor<DefaultScriptDependenciesProvider>(
+            "org.jetbrains.kotlin.defaultScriptDependenciesProvider",
+            DefaultScriptDependenciesProvider::class.java
+    )
+
+}