IDEA-120694 collapsing one liners is overly eager

java/java-psi-impl/src/com/intellij/codeInsight/folding/impl/JavaFoldingBuilderBase.java

@@ -69,11 +69,23 @@ public abstract class JavaFoldingBuilderBase extends CustomFoldingBuilder implem
     return "...";
   }
 
+  private static boolean areOnAdjacentLines(PsiElement e1, PsiElement e2) {
+    Document document = e1.getContainingFile().getViewProvider().getDocument();
+    return document != null &&
+           document.getLineNumber(e1.getTextRange().getEndOffset()) + 1 == document.getLineNumber(e2.getTextRange().getStartOffset());
+  }
+
   private static boolean isSimplePropertyAccessor(PsiMethod method) {
     PsiCodeBlock body = method.getBody();
     if (body == null || body.getLBrace() == null || body.getRBrace() == null) return false;
     PsiStatement[] statements = body.getStatements();
     if (statements.length == 0) return false;
+
+    if (!areOnAdjacentLines(body.getLBrace(), statements[0]) || !areOnAdjacentLines(statements[statements.length - 1], body.getRBrace())) {
+      //the user might intend to type at an empty line
+      return false;
+    }
+
     PsiStatement statement = statements[0];
     if (PropertyUtil.isSimplePropertyGetter(method)) {
       if (statement instanceof PsiReturnStatement) {

java/java-tests/testSrc/com/intellij/codeInsight/folding/JavaFoldingTest.groovy

@@ -457,6 +457,7 @@ class Test {
     configure """class Foo {
  int field;
  int field2;
+ int field3;
  
  int getField()
  {
@@ -467,12 +468,18 @@ class Test {
    field = f;
  }
  
- void setField2(int f){field2=f;}
+ void setField2(int f){field2=f;} // normal method folding here
+
+  // normal method folding here
+ void setField3(int f){
+   
+   field2=f;
+ }
 
 }"""
     PsiClass fooClass = JavaPsiFacade.getInstance(project).findClass('Foo', GlobalSearchScope.allScope(project))
     def regions = myFixture.editor.foldingModel.allFoldRegions.sort { it.startOffset }
-    assert regions.size() == 5
+    assert regions.size() == 6
     
     Closure checkAccessorFolding = { FoldRegion region1, FoldRegion region2, PsiMethod method ->
       assert region1.startOffset == method.parameterList.textRange.endOffset
@@ -489,6 +496,7 @@ class Test {
     checkAccessorFolding(regions[2], regions[3], fooClass.methods[1])
     
     assert regions[4].placeholderText == '{...}'
+    assert regions[5].placeholderText == '{...}'
   }
 
   private def changeFoldRegions(Closure op) {