Implement Smart Enter handler for class body (#1022)

Fixes #KT-9011

idea/src/org/jetbrains/kotlin/idea/editor/KotlinSmartEnterHandler.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,7 +58,9 @@ class KotlinSmartEnterHandler: SmartEnterProcessorWithFixers() {
 
                 KotlinLastLambdaParameterFixer(),
 
-                KotlinClassInitializerFixer()
+                KotlinClassInitializerFixer(),
+
+                KotlinClassBodyFixer()
         )
 
         addEnterProcessors(KotlinPlainEnterProcessor())
@@ -71,13 +73,13 @@ class KotlinSmartEnterHandler: SmartEnterProcessorWithFixers() {
 
         while (atCaret != null) {
             when {
-                atCaret.isKotlinStatement() == true -> return atCaret
+                atCaret.isKotlinStatement() -> return atCaret
                 atCaret.parent is KtFunctionLiteral -> return atCaret
                 atCaret is KtDeclaration -> {
                     val declaration = atCaret
                     when {
                         declaration is KtParameter && !declaration.isInLambdaExpression() -> {/* proceed to function declaration */}
-                        declaration.getParent() is KtForExpression -> {/* skip variable declaration in 'for' expression */}
+                        declaration.parent is KtForExpression -> {/* skip variable declaration in 'for' expression */}
                         else -> return atCaret
                     }
                 }

idea/src/org/jetbrains/kotlin/idea/editor/fixers/KotlinClassBodyFixer.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.editor.fixers
+
+import com.intellij.lang.SmartEnterProcessorWithFixers
+import com.intellij.openapi.editor.Editor
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.idea.editor.KotlinSmartEnterHandler
+import org.jetbrains.kotlin.psi.KtClassOrObject
+import org.jetbrains.kotlin.psi.psiUtil.endOffset
+
+class KotlinClassBodyFixer : SmartEnterProcessorWithFixers.Fixer<KotlinSmartEnterHandler>() {
+    override fun apply(editor: Editor, processor: KotlinSmartEnterHandler, psiElement: PsiElement) {
+        if (psiElement !is KtClassOrObject) return
+        if (psiElement.getBody() != null) return
+
+        val doc = editor.document
+        val endOffset = psiElement.range.end
+
+        editor.caretModel.moveToOffset(psiElement.endOffset - 1)
+
+        // Insert '\n' to force a multiline body, otherwise there will be an empty body on one line and a caret on the next one.
+        doc.insertString(endOffset, "{\n}")
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/codeInsight/smartEnter/SmartEnterTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -1356,6 +1356,30 @@ class SmartEnterTest : KotlinLightCodeInsightFixtureTestCase() {
             """
     )
 
+    fun testClassBody1() = doFileTest(
+            """
+            class Foo<caret>
+            """
+            ,
+            """
+            class Foo {
+                <caret>
+            }
+            """
+    )
+
+    fun testClassBody2() = doFileTest(
+            """
+            class <caret>Foo
+            """
+            ,
+            """
+            class Foo {
+                <caret>
+            }
+            """
+    )
+
     fun doFunTest(before: String, after: String) {
         fun String.withFunContext(): String {
             val bodyText = "//----\n${this.trimIndent()}\n//----"