In progress: KT-7442 Inspection + intention to replace "if (xxx == null) return ..' with elvis

compiler/frontend/src/org/jetbrains/kotlin/psi/JetPsiUtil.java

@@ -551,6 +551,11 @@ public class JetPsiUtil {
             return true;
         }
 
+        // 'x ?: ...' case
+        if (parentExpression instanceof JetBinaryExpression && parentOperation == JetTokens.ELVIS && currentInner == ((JetBinaryExpression) parentExpression).getRight()) {
+            return false;
+        }
+
         int innerPriority = getPriority(innerExpression);
         int parentPriority = getPriority(parentExpression);
 

idea/src/META-INF/plugin.xml

@@ -498,6 +498,11 @@
         language="jet"
         implementationClass="org.jetbrains.kotlin.idea.search.ideaExtensions.JetTargetElementEvaluator" />
 
+    <intentionAction>
+      <className>org.jetbrains.kotlin.idea.intentions.IfNullToElvisIntention</className>
+      <category>Kotlin</category>
+    </intentionAction>
+
     <intentionAction>
       <className>org.jetbrains.kotlin.idea.intentions.SpecifyTypeExplicitlyAction</className>
       <category>Kotlin</category>

idea/src/org/jetbrains/kotlin/idea/intentions/IfNullToElvisIntention.kt

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2010-2015 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.intentions
+
+import com.intellij.openapi.editor.Editor
+import com.intellij.psi.PsiComment
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiExpression
+import com.intellij.psi.PsiRecursiveElementVisitor
+import org.jetbrains.kotlin.JetNodeTypes
+import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.util.isNothing
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.replaced
+import org.jetbrains.kotlin.psi.psiUtil.siblings
+import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
+import java.util.ArrayList
+
+public class IfNullToElvisIntention : JetSelfTargetingIntention<JetIfExpression>(javaClass(), "Replace 'if' with elvis operator"){
+    override fun isApplicableTo(element: JetIfExpression, caretOffset: Int): Boolean {
+        //TODO: range!
+        val data = calcData(element) ?: return false
+
+        val type = data.ifNullExpression.analyze().getType(data.ifNullExpression) ?: return false
+        if (!type.isNothing()) return false
+
+        return true
+    }
+
+    override fun applyTo(element: JetIfExpression, editor: Editor) {
+        val (initializer, statement, ifNullExpr) = calcData(element)!!
+        val factory = JetPsiFactory(element)
+
+        // do not loose any comments!
+        val comments = element.extractComments(ifNullExpr)
+
+        for (comment in comments) {
+            statement.add(factory.createWhiteSpace())
+            statement.add(comment)
+        }
+
+        val elvis = factory.createExpression("a ?: b") as JetBinaryExpression
+        elvis.getLeft()!!.replace(initializer)
+        elvis.getRight()!!.replace(ifNullExpr)
+        val newElvis = initializer.replaced(elvis)
+        element.delete()
+
+        editor.getCaretModel().moveToOffset(newElvis.getRight()!!.getTextOffset())
+    }
+
+    private data class Data(
+            val initializer: JetExpression,
+            val statement: JetExpression,
+            val ifNullExpression: JetExpression
+    )
+
+    private fun calcData(ifExpression: JetIfExpression): Data? {
+        if (ifExpression.getElse() != null) return null
+
+        val binaryExpression = ifExpression.getCondition() as? JetBinaryExpression ?: return null
+        if (binaryExpression.getRight()?.getNode()?.getElementType() != JetNodeTypes.NULL) return null
+        val left = binaryExpression.getLeft() as? JetSimpleNameExpression ?: return null
+
+        if (ifExpression.getParent() !is JetBlockExpression) return null
+        val prevStatement = ifExpression.siblings(forward = false, withItself = false)
+                                    .firstIsInstanceOrNull<JetExpression>() ?: return null
+        if (prevStatement !is JetVariableDeclaration) return null
+        if (prevStatement.getNameAsName() != left.getReferencedNameAsName()) return null
+        val initializer = prevStatement.getInitializer() ?: return null
+        val then = ifExpression.getThen() ?: return null
+
+        if (then is JetBlockExpression) {
+            val statement = then.getStatements().singleOrNull() as? JetExpression ?: return null
+            return Data(initializer, prevStatement, statement)
+        }
+        else {
+            return Data(initializer, prevStatement, then)
+        }
+    }
+
+    private fun PsiElement.extractComments(skipElement: PsiElement): List<PsiComment> {
+        val comments = ArrayList<PsiComment>()
+        accept(object : PsiRecursiveElementVisitor() {
+            override fun visitElement(element: PsiElement) {
+                if (element == skipElement) return
+                super.visitElement(element)
+            }
+
+            override fun visitComment(comment: PsiComment) {
+                comments.add(comment)
+            }
+        })
+        return comments
+    }
+}

idea/testData/intentions/ifNullToElvis/.intention

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.intentions.IfNullToElvisIntention

idea/testData/intentions/ifNullToElvis/Break.kt

@@ -0,0 +1,6 @@
+fun foo(p: List<String?>) {
+    for (i in 1..10) {
+        val v = p[i]
+        <caret>if (v == null) break
+    }
+}

idea/testData/intentions/ifNullToElvis/Break.kt.after

@@ -0,0 +1,5 @@
+fun foo(p: List<String?>) {
+    for (i in 1..10) {
+        val v = p[i] ?: <caret>break
+    }
+}

idea/testData/intentions/ifNullToElvis/CommentInBlock.kt

@@ -0,0 +1,8 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0]
+    <caret>if (v == null) {
+        // return -1 if null
+        return -1
+    }
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/CommentInBlock.kt.after

@@ -0,0 +1,4 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0] ?: <caret>return -1 // return -1 if null
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Comments.kt

@@ -0,0 +1,6 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0]
+    // now check if v is null
+    <caret>if (v == null/* null */) return -1 // return -1
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Comments.kt.after

@@ -0,0 +1,6 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0] ?: <caret>return -1 /* null */
+    // now check if v is null
+    // return -1
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Comments2.kt

@@ -0,0 +1,8 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0]
+    <caret>if (v == null) { // v is null
+        // we should do something with it
+        return -1 // let's return -1
+    } // end of if
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Comments2.kt.after

@@ -0,0 +1,5 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0] ?: <caret>return -1 // v is null // we should do something with it // let's return -1
+    // end of if
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Continue.kt

@@ -0,0 +1,6 @@
+fun foo(p: List<String?>) {
+    for (i in 1..10) {
+        val v = p[i]
+        <caret>if (v == null) continue
+    }
+}

idea/testData/intentions/ifNullToElvis/Continue.kt.after

@@ -0,0 +1,5 @@
+fun foo(p: List<String?>) {
+    for (i in 1..10) {
+        val v = p[i] ?: <caret>continue
+    }
+}

idea/testData/intentions/ifNullToElvis/MultiStatementBlock.kt

@@ -0,0 +1,10 @@
+// IS_APPLICABLE: false
+fun foo(p: List<String?>) {
+    val v = p[0]
+    <caret>if (v == null) {
+        bar()
+        return
+    }
+}
+
+fun bar(){}

idea/testData/intentions/ifNullToElvis/NotExit.kt

@@ -0,0 +1,8 @@
+// IS_APPLICABLE: false
+fun foo(p: List<String?>): Int? {
+    val v = p[0]
+    <caret>if (v == null) bar()
+    return v?.length()
+}
+
+fun bar(){}

idea/testData/intentions/ifNullToElvis/OtherVar1.kt

@@ -0,0 +1,11 @@
+// IS_APPLICABLE: false
+class C {
+    var v: String? = null
+
+    fun foo(p: List<String?>): Int {
+        val v = p[0]
+        <caret>if (this.v == null) return -1
+        return v!!.length()
+    }
+}
+

idea/testData/intentions/ifNullToElvis/OtherVar2.kt

@@ -0,0 +1,11 @@
+// IS_APPLICABLE: false
+class C {
+    var x: String? = null
+
+    fun foo(p: List<String?>): Int {
+        val v = p[0]
+        <caret>if (x == null) return -1
+        return v!!.length()
+    }
+}
+

idea/testData/intentions/ifNullToElvis/Return.kt

@@ -0,0 +1,5 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0]
+    <caret>if (v == null) return -1
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/Return.kt.after

@@ -0,0 +1,4 @@
+fun foo(p: List<String?>): Int {
+    val v = p[0] ?: <caret>return -1
+    return v.length()
+}

idea/testData/intentions/ifNullToElvis/ThrowInBlock.kt

@@ -0,0 +1,8 @@
+// WITH_RUNTIME
+
+fun foo(p: List<String?>) {
+    val v = p[0]
+    <caret>if (v == null) {
+        throw RuntimeException()
+    }
+}

idea/testData/intentions/ifNullToElvis/ThrowInBlock.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun foo(p: List<String?>) {
+    val v = p[0] ?: <caret>throw RuntimeException()
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -4094,6 +4094,81 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
         }
     }
 
+    @TestMetadata("idea/testData/intentions/ifNullToElvis")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class IfNullToElvis extends AbstractIntentionTest {
+        public void testAllFilesPresentInIfNullToElvis() throws Exception {
+            JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/intentions/ifNullToElvis"), Pattern.compile("^(.+)\\.kt$"), true);
+        }
+
+        @TestMetadata("Break.kt")
+        public void testBreak() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/Break.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("CommentInBlock.kt")
+        public void testCommentInBlock() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/CommentInBlock.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("Comments.kt")
+        public void testComments() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/Comments.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("Comments2.kt")
+        public void testComments2() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/Comments2.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("Continue.kt")
+        public void testContinue() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/Continue.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("MultiStatementBlock.kt")
+        public void testMultiStatementBlock() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/MultiStatementBlock.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("NotExit.kt")
+        public void testNotExit() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/NotExit.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("OtherVar1.kt")
+        public void testOtherVar1() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/OtherVar1.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("OtherVar2.kt")
+        public void testOtherVar2() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/OtherVar2.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("Return.kt")
+        public void testReturn() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/Return.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("ThrowInBlock.kt")
+        public void testThrowInBlock() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/ifNullToElvis/ThrowInBlock.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("idea/testData/intentions/insertCurlyBracesToTemplate")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)