IDEA-130703 Join Lines (Ctrl-Shift-J) could join nested if's

java/java-impl/src/META-INF/JavaPlugin.xml

@@ -406,6 +406,7 @@
              order="before explicitlyImported"/>
     <weigher key="proximity" implementationClass="com.intellij.psi.util.proximity.ReferenceListWeigher" id="referenceList"
              order="before samePsiMember"/>
+    <joinLinesHandler implementation="com.intellij.codeInsight.editorActions.NestedIfJoinLinesHandler"/>
     <joinLinesHandler implementation="com.intellij.codeInsight.editorActions.BlockJoinLinesHandler"/>
     <joinLinesHandler implementation="com.intellij.codeInsight.editorActions.ChainCallJoinLinesHandler"/>
     <joinLinesHandler implementation="com.intellij.codeInsight.editorActions.AssignmentSequenceJoinLinesHandler"/>

java/java-impl/src/com/intellij/codeInsight/editorActions/NestedIfJoinLinesHandler.java

@@ -0,0 +1,64 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.codeInsight.editorActions;
+
+import com.intellij.openapi.editor.Document;
+import com.intellij.psi.*;
+import com.intellij.psi.util.PsiTreeUtil;
+import com.siyeh.ig.psiutils.CommentTracker;
+import com.siyeh.ig.psiutils.ControlFlowUtils;
+import com.siyeh.ig.psiutils.ParenthesesUtils;
+import org.jetbrains.annotations.NotNull;
+
+import static com.intellij.util.ObjectUtils.tryCast;
+
+/**
+ * <pre>{@code
+ * if(a) {
+ *   if(b) {
+ *     ...
+ *   }
+ * }
+ * =>
+ * if(a && b) {
+ *   ...
+ * }
+ * }</pre>
+ */
+public class NestedIfJoinLinesHandler implements JoinLinesHandlerDelegate {
+  @Override
+  public int tryJoinLines(@NotNull final Document document, @NotNull final PsiFile psiFile, final int start, final int end) {
+    PsiJavaToken elementAtStartLineEnd = tryCast(psiFile.findElementAt(start), PsiJavaToken.class);
+    PsiElement nextLineElement = psiFile.findElementAt(end);
+    if (elementAtStartLineEnd == null || nextLineElement == null) return CANNOT_JOIN;
+    PsiIfStatement outerIf = null;
+    if (elementAtStartLineEnd.getTokenType().equals(JavaTokenType.RPARENTH)) {
+      outerIf = tryCast(elementAtStartLineEnd.getParent(), PsiIfStatement.class);
+    } else if(elementAtStartLineEnd.getTokenType().equals(JavaTokenType.LBRACE)) {
+      PsiCodeBlock block = tryCast(elementAtStartLineEnd.getParent(), PsiCodeBlock.class);
+      if (block != null) {
+        PsiBlockStatement blockStatement = tryCast(block.getParent(), PsiBlockStatement.class);
+        if (blockStatement != null) {
+          outerIf = tryCast(blockStatement.getParent(), PsiIfStatement.class);
+          if (outerIf == null || outerIf.getThenBranch() != blockStatement) return CANNOT_JOIN;
+        }
+      }
+    }
+    if (outerIf == null || outerIf.getElseBranch() != null) return CANNOT_JOIN;
+    PsiIfStatement innerIf = tryCast(ControlFlowUtils.stripBraces(outerIf.getThenBranch()), PsiIfStatement.class);
+    if (!PsiTreeUtil.isAncestor(innerIf, nextLineElement, false)) return CANNOT_JOIN;
+    if (innerIf.getThenBranch() == null || innerIf.getElseBranch() != null) return CANNOT_JOIN;
+
+    PsiExpression outerCondition = outerIf.getCondition();
+    if (outerCondition == null) return CANNOT_JOIN;
+    PsiExpression innerCondition = innerIf.getCondition();
+    if (innerCondition == null) return CANNOT_JOIN;
+
+    CommentTracker ct = new CommentTracker();
+    String childConditionText = ParenthesesUtils.getText(ct.markUnchanged(innerCondition), ParenthesesUtils.OR_PRECEDENCE);
+    String parentConditionText = ParenthesesUtils.getText(ct.markUnchanged(outerCondition), ParenthesesUtils.OR_PRECEDENCE);
+
+    PsiBinaryExpression newCondition = (PsiBinaryExpression)ct.replace(outerCondition, parentConditionText + "&&" + childConditionText);
+    ct.replaceAndRestoreComments(outerIf.getThenBranch(), innerIf.getThenBranch());
+    return newCondition.getOperationSign().getTextRange().getStartOffset();
+  }
+}

java/java-tests/testData/codeInsight/joinLines/IfChain.java

@@ -0,0 +1,9 @@
+class Foo {
+    void test(int a, int b) {
+        <caret>if(a > 0) {
+            if(b < 0) {
+                System.out.println(a+b);
+            }
+        }
+    }
+}

java/java-tests/testData/codeInsight/joinLines/IfChainElse.java

@@ -0,0 +1,11 @@
+class Foo {
+    void test(int a, int b) {
+        <caret>if(a > 0) {
+            if(b < 0) {
+                System.out.println(a+b);
+            } else {
+                System.out.println(a-b);
+            }
+        }
+    }
+}

java/java-tests/testData/codeInsight/joinLines/IfChainElse_after.java

@@ -0,0 +1,9 @@
+class Foo {
+    void test(int a, int b) {
+        if(a > 0) if(b < 0) {
+                System.out.println(a+b);
+            } else {
+                System.out.println(a-b);
+            }
+    }
+}

java/java-tests/testData/codeInsight/joinLines/IfChainNoBraces.java

@@ -0,0 +1,6 @@
+class Foo {
+    void test(int a, int b) {
+        <caret>if(a > 0)
+            if (b < 0) System.out.println(a + b);
+    }
+}

java/java-tests/testData/codeInsight/joinLines/IfChainNoBraces_after.java

@@ -0,0 +1,5 @@
+class Foo {
+    void test(int a, int b) {
+        if(a > 0 && b < 0) System.out.println(a + b);
+    }
+}

java/java-tests/testData/codeInsight/joinLines/IfChain_after.java

@@ -0,0 +1,7 @@
+class Foo {
+    void test(int a, int b) {
+        if(a > 0 && b < 0) {
+                System.out.println(a+b);
+            }
+    }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/JoinLinesTest.java

@@ -50,6 +50,10 @@ public class JoinLinesTest extends LightCodeInsightTestCase {
   public void testDeclarationAndReassignmentWithCall() { doTest(); }
   public void testAssignmentAndReassignmentWithCall() { doTest(); }
 
+  public void testIfChain() { doTest(); }
+  public void testIfChainNoBraces() { doTest(); }
+  public void testIfChainElse() { doTest(); }
+
   public void testSCR3493() {
     CommonCodeStyleSettings settings = getJavaSettings();
     boolean use_tab_character = settings.getIndentOptions().USE_TAB_CHARACTER;