IDEA-196178 Join Lines on selected text also joins not selected text

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

@@ -0,0 +1,14 @@
+class Foo {
+    void test() {
+        int a = 2;
+        int b = 2;
+
+        <selection>if (a == b){
+            if (a > b){
+                System.out.println();
+            }
+        }</selection>
+
+        System.out.println();
+    }
+}

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

@@ -0,0 +1,10 @@
+class Foo {
+    void test() {
+        int a = 2;
+        int b = 2;
+
+        if (a == b && a > b) System.out.println();
+
+        System.out.println();
+    }
+}

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

@@ -56,6 +56,7 @@ public class JoinLinesTest extends LightCodeInsightTestCase {
   public void testIfChainPolyadic() { doTest(); }
   public void testIfChainNoBraces() { doTest(); }
   public void testIfChainElse() { doTest(); }
+  public void testIfChainSelection() { doTest(); }
 
   public void testSCR3493() {
     CommonCodeStyleSettings settings = getJavaSettings();

platform/lang-impl/src/com/intellij/codeInsight/editorActions/JoinLinesHandler.java

@@ -88,11 +88,16 @@ public class JoinLinesHandler extends EditorActionHandler {
         Ref<Integer> caretRestoreOffset = new Ref<>(-1);
         CodeEditUtil.setNodeReformatStrategy(node -> node.getTextRange().getStartOffset() >= startReformatOffset);
         try {
-          for (int count = 0; count < lineCount; count++) {
+          int count = 0;
+          while (count < lineCount) {
             indicator.checkCanceled();
             indicator.setFraction(((double)count) / lineCount);
+            int beforeLines = doc.getLineCount();
             ProgressManager.getInstance().executeNonCancelableSection(
               () -> doJoinTwoLines(doc, project, docManager, psiFile, line, caretRestoreOffset));
+            int afterLines = doc.getLineCount();
+            // Single Join two lines procedure could join more than two (e.g. if it removes braces)
+            count += Math.max(beforeLines - afterLines, 1);
           }
         }
         finally {