Delete/Move: Delete entire file when deleting top-level class or object and no other top-level declarations are present. Ask the user confirmation if deletion if caused by the Move refactoring

#KT-8033 Fixed

compiler/frontend/src/org/jetbrains/kotlin/psi/JetClassOrObject.kt

@@ -16,10 +16,13 @@
 
 package org.jetbrains.kotlin.psi
 
+import com.intellij.lang.ASTNode
 import com.intellij.lang.ASTNode
 import com.intellij.navigation.ItemPresentation
 import com.intellij.navigation.ItemPresentationProviders
 import com.intellij.psi.PsiElement
+import com.intellij.psi.impl.CheckUtil
+import com.intellij.psi.impl.source.codeStyle.CodeEditUtil
 import com.intellij.psi.stubs.IStubElementType
 import org.jetbrains.kotlin.JetNodeTypes
 import org.jetbrains.kotlin.lexer.JetTokens
@@ -62,4 +65,16 @@ abstract public class JetClassOrObject : JetTypeParameterListOwnerStub<KotlinCla
     public fun getSecondaryConstructors(): List<JetSecondaryConstructor> = getBody()?.getSecondaryConstructors().orEmpty()
 
     public fun isAnnotation(): Boolean = hasModifier(JetTokens.ANNOTATION_KEYWORD)
+
+    public override fun delete() {
+        CheckUtil.checkWritable(this);
+
+        val file = getContainingJetFile();
+        if (!isTopLevel() || file.getDeclarations().size() > 1) {
+            CodeEditUtil.removeChild(getParent().getNode(), getNode());
+        }
+        else {
+            file.delete();
+        }
+    }
 }

idea/idea-core/src/org/jetbrains/kotlin/idea/core/psiModificationUtils.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.idea.core
 
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiWhiteSpace
+import com.intellij.psi.impl.source.codeStyle.CodeEditUtil
 import com.intellij.psi.util.PsiTreeUtil
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil
@@ -149,3 +150,7 @@ private fun deleteElementWithDelimiters(element: PsiElement) {
 
     parent.deleteChildRange(from, to)
 }
+
+public fun PsiElement.deleteSingle() {
+    CodeEditUtil.removeChild(getParent()?.getNode() ?: return, getNode() ?: return)
+}

idea/src/org/jetbrains/kotlin/idea/refactoring/move/moveTopLevelDeclarations/MoveKotlinTopLevelDeclarationsProcessor.kt

@@ -45,6 +45,7 @@ import org.jetbrains.kotlin.asJava.toLightElements
 import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde
 import org.jetbrains.kotlin.idea.codeInsight.JetFileReferencesResolver
 import org.jetbrains.kotlin.idea.codeInsight.shorten.addToShorteningWaitSet
+import org.jetbrains.kotlin.idea.core.deleteSingle
 import org.jetbrains.kotlin.idea.core.refactoring.getUsageContext
 import org.jetbrains.kotlin.idea.refactoring.JetRefactoringBundle
 import org.jetbrains.kotlin.idea.refactoring.fqName.getKotlinFqName
@@ -68,7 +69,7 @@ trait Mover: (originalElement: JetNamedDeclaration, targetFile: JetFile) -> JetN
     object Default: Mover {
         override fun invoke(originalElement: JetNamedDeclaration, targetFile: JetFile): JetNamedDeclaration {
             val newElement = targetFile.add(originalElement) as JetNamedDeclaration
-            originalElement.delete()
+            originalElement.deleteSingle()
             return newElement
         }
     }

idea/src/org/jetbrains/kotlin/idea/refactoring/safeDelete/KotlinSafeDeleteProcessor.kt

@@ -37,12 +37,12 @@ import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.idea.JetBundle
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.core.deleteElementAndCleanParent
 import org.jetbrains.kotlin.idea.refactoring.JetRefactoringUtil
 import org.jetbrains.kotlin.idea.references.JetReference
 import org.jetbrains.kotlin.idea.search.usagesSearch.processDelegationCallConstructorUsages
 import org.jetbrains.kotlin.lexer.JetTokens
 import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.idea.core.deleteElementAndCleanParent
 import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
 import org.jetbrains.kotlin.resolve.BindingContext
 import java.util.ArrayList
@@ -326,18 +326,4 @@ public class KotlinSafeDeleteProcessor : JavaSafeDeleteProcessor() {
             else -> super.getElementsToSearch(element, module, allElementsToDelete)
         }
     }
-
-    override fun getAdditionalElementsToDelete(
-            element: PsiElement,
-            allElementsToDelete: MutableCollection<PsiElement>,
-            askUser: Boolean
-    ): Collection<PsiElement> {
-        val filesToDelete = allElementsToDelete
-                .filter { it is JetNamedDeclaration && it.getContainingJetFile() == it.getParent() }
-                .groupBy { (it as JetNamedDeclaration).getContainingJetFile() }
-                .filter { it.getKey().getDeclarations().size() == it.getValue().size() }
-                .keySet()
-        return super.getAdditionalElementsToDelete(element, allElementsToDelete, askUser)?.let { it + filesToDelete }
-               ?: filesToDelete
-    }
 }