Find Usages: Properly select primary element for Find Usages Dialog. Avoid delegating handler when there is only one primary element

#KT-7048 Fixed

idea/src/org/jetbrains/kotlin/idea/findUsages/KotlinFindUsagesHandlerFactory.kt

@@ -29,6 +29,7 @@ import com.intellij.find.findUsages.JavaFindUsagesHandlerFactory
 import org.jetbrains.kotlin.idea.findUsages.handlers.DelegatingFindMemberUsagesHandler
 import org.jetbrains.kotlin.plugin.findUsages.handlers.KotlinFindUsagesHandlerDecorator
 import com.intellij.openapi.extensions.Extensions
+import org.jetbrains.kotlin.asJava.unwrapped
 import org.jetbrains.kotlin.psi.*
 
 public class KotlinFindUsagesHandlerFactory(project: Project) : FindUsagesHandlerFactory() {
@@ -57,7 +58,19 @@ public class KotlinFindUsagesHandlerFactory(project: Project) : FindUsagesHandle
 
                 if (forHighlightUsages) return KotlinFindMemberUsagesHandler.getInstance(declaration, this)
                 JetRefactoringUtil.checkSuperMethods(declaration, null, "super.methods.action.key.find.usages")?.let { callables ->
-                    if (callables.empty) FindUsagesHandler.NULL_HANDLER else DelegatingFindMemberUsagesHandler(declaration, callables, this)
+                    when (callables.size()) {
+                        0 -> FindUsagesHandler.NULL_HANDLER
+                        1 -> {
+                            val target = callables.first().unwrapped ?: return FindUsagesHandler.NULL_HANDLER
+                            if (target is JetNamedDeclaration) {
+                                KotlinFindMemberUsagesHandler.getInstance(target, this)
+                            }
+                            else {
+                                javaHandlerFactory.createFindUsagesHandler(target, false)
+                            }
+                        }
+                        else -> DelegatingFindMemberUsagesHandler(declaration, callables, this)
+                    }
                 }
             }
 

idea/src/org/jetbrains/kotlin/idea/findUsages/handlers/DelegatingFindMemberUsagesHandler.kt

@@ -16,24 +16,20 @@
 
 package org.jetbrains.kotlin.idea.findUsages.handlers
 
+import com.intellij.find.findUsages.AbstractFindUsagesDialog
 import com.intellij.find.findUsages.FindUsagesHandler
+import com.intellij.find.findUsages.FindUsagesOptions
+import com.intellij.find.findUsages.JavaFindUsagesHandler
+import com.intellij.openapi.actionSystem.DataContext
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiMethod
 import com.intellij.usageView.UsageInfo
 import com.intellij.util.Processor
-import com.intellij.find.findUsages.FindUsagesOptions
 import org.jetbrains.kotlin.idea.findUsages.KotlinFindUsagesHandlerFactory
-import kotlin.properties.Delegates
-import org.jetbrains.kotlin.psi.JetNamedDeclaration
-import com.intellij.psi.PsiMethod
-import com.intellij.find.findUsages.JavaFindUsagesHandler
 import org.jetbrains.kotlin.idea.findUsages.KotlinFunctionFindUsagesOptions
 import org.jetbrains.kotlin.idea.findUsages.toJavaMethodOptions
-import com.intellij.openapi.actionSystem.DataContext
+import org.jetbrains.kotlin.psi.JetNamedDeclaration
-import com.intellij.openapi.components.ServiceManager
+import kotlin.properties.Delegates
-import com.intellij.psi.xml.XmlAttribute
-import org.jetbrains.kotlin.psi.JetProperty
-import com.intellij.find.findUsages.JavaVariableFindUsagesOptions
-import java.util.ArrayList
 
 class DelegatingFindMemberUsagesHandler(
         val declaration: JetNamedDeclaration,
@@ -42,10 +38,6 @@ class DelegatingFindMemberUsagesHandler(
 ) : FindUsagesHandler(declaration) {
     private val kotlinHandler = KotlinFindMemberUsagesHandler.getInstance(declaration, elementsToSearch, factory)
 
-    private val javaHandler: JavaFindUsagesHandler by Delegates.lazy {
-        JavaFindUsagesHandler(declaration, elementsToSearch.copyToArray(), factory.javaHandlerFactory)
-    }
-
     private fun getHandler(element: PsiElement): FindUsagesHandler? =
             when (element) {
                 is JetNamedDeclaration ->
@@ -57,6 +49,11 @@ class DelegatingFindMemberUsagesHandler(
                 else -> null
             }
 
+    override fun getFindUsagesDialog(isSingleFile: Boolean, toShowInNewTab: Boolean, mustOpenInNewTab: Boolean): AbstractFindUsagesDialog {
+        return getHandler(getPsiElement())?.getFindUsagesDialog(isSingleFile, toShowInNewTab, mustOpenInNewTab)
+               ?: super.getFindUsagesDialog(isSingleFile, toShowInNewTab, mustOpenInNewTab)
+    }
+
     override fun getPrimaryElements(): Array<PsiElement> {
         return kotlinHandler.getPrimaryElements()
     }