reimplement fix 6fb3647 to account for another use case - update of folding placeholder text depending on folded text region

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

@@ -1217,6 +1217,33 @@ class Foo {
     myFixture.doHighlighting()
     assertTopLevelFoldRegionsState "[FoldRegion +(24:83), placeholder='{...}']"
   }
+  
+  public void "test placeholder update on refactoring"() {
+    configure """\
+class Foo {
+  void method() {}
+  
+  Foo foo = new Foo() {
+    void method() {
+      System.out.println();
+    }
+  };
+}
+"""
+    assertTopLevelFoldRegionsState "[FoldRegion +(46:84), placeholder='method() → { ', FoldRegion +(105:115), placeholder=' }']"
+    
+    // emulate rename refactoring ('method' to 'otherMethod')
+    def document = myFixture.editor.document
+    WriteCommandAction.runWriteCommandAction myFixture.project, {
+      int pos;
+      while ((pos = document.getText().indexOf("method")) >= 0) {
+        document.replaceString(pos, pos + "method".length(), "otherMethod")
+      }
+    }    
+
+    myFixture.doHighlighting()
+    assertTopLevelFoldRegionsState "[FoldRegion +(51:94), placeholder='otherMethod() → { ', FoldRegion +(115:125), placeholder=' }']"
+  }
 
   private void assertTopLevelFoldRegionsState(String expectedState) {
     assertEquals(expectedState, myFixture.editor.foldingModel.toString())

platform/lang-impl/src/com/intellij/codeInsight/folding/impl/UpdateFoldRegionsOperation.java

@@ -93,6 +93,8 @@ class UpdateFoldRegionsOperation implements Runnable {
     List<FoldRegion> newRegions = addNewRegions(info, foldingModel, elementsToFold, rangeToExpandStatusMap, shouldExpand, groupExpand);
 
     applyExpandStatus(newRegions, shouldExpand, groupExpand);
+    
+    foldingModel.clearDocumentRangesModificationStatus();
   }
 
   private static void applyExpandStatus(@NotNull List<FoldRegion> newRegions,
@@ -248,7 +250,10 @@ class UpdateFoldRegionsOperation implements Runnable {
   }
 
   private boolean regionCanBeRemovedWhenCollapsed(FoldRegion region) {
-    return Boolean.TRUE.equals(region.getUserData(CAN_BE_REMOVED_WHEN_COLLAPSED)) || !region.isValid() || isRegionInCaretLine(region);
+    return Boolean.TRUE.equals(region.getUserData(CAN_BE_REMOVED_WHEN_COLLAPSED)) ||
+           ((FoldingModelEx)myEditor.getFoldingModel()).hasDocumentRegionChangedFor(region) ||
+           !region.isValid() ||
+           isRegionInCaretLine(region);
   }
 
   private boolean isRegionInCaretLine(FoldRegion region) {

platform/lang-impl/src/com/intellij/injected/editor/FoldingModelWindow.java

@@ -200,6 +200,14 @@ class FoldingModelWindow implements FoldingModelEx{
     return result;
   }
 
+  @Override
+  public void clearDocumentRangesModificationStatus() {}
+
+  @Override
+  public boolean hasDocumentRegionChangedFor(@NotNull FoldRegion region) {
+    return false;
+  }
+
   @Override
   public void clearFoldRegions() {
     myDelegate.clearFoldRegions();

platform/platform-impl/src/com/intellij/openapi/editor/ex/FoldingModelEx.java

@@ -64,4 +64,8 @@ public interface FoldingModelEx extends FoldingModel {
   
   @NotNull
   List<FoldRegion> getGroupedRegions(FoldingGroup group);
+  
+  void clearDocumentRangesModificationStatus();
+  
+  boolean hasDocumentRegionChangedFor(@NotNull FoldRegion region);
 }

platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldRegionImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * Copyright 2000-2016 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.
@@ -27,6 +27,7 @@ package com.intellij.openapi.editor.impl;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.FoldRegion;
 import com.intellij.openapi.editor.FoldingGroup;
+import com.intellij.openapi.editor.event.DocumentEvent;
 import com.intellij.openapi.editor.ex.DocumentEx;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -37,6 +38,7 @@ class FoldRegionImpl extends RangeMarkerImpl implements FoldRegion {
   private final String myPlaceholderText;
   private final FoldingGroup myGroup;
   private final boolean myShouldNeverExpand;
+  private boolean myDocumentRegionWasChanged;
 
   FoldRegionImpl(@NotNull Editor editor,
                  int startOffset,
@@ -119,6 +121,26 @@ class FoldRegionImpl extends RangeMarkerImpl implements FoldRegion {
   public boolean shouldNeverExpand() {
     return myShouldNeverExpand;
   }
+  
+  boolean hasDocumentRegionChanged() {
+    return myDocumentRegionWasChanged;
+  }
+  
+  void resetDocumentRegionChanged() {
+    myDocumentRegionWasChanged = false;
+  }
+
+  @Override
+  protected void changedUpdateImpl(@NotNull DocumentEvent e) {
+    if (isValid()) {
+      int oldStart = intervalStart();
+      int oldEnd = intervalEnd();
+      int changeStart = e.getOffset();
+      int changeEnd = e.getOffset() + e.getOldLength();
+      if (changeStart < oldEnd && changeEnd > oldStart) myDocumentRegionWasChanged = true;
+    }
+    super.changedUpdateImpl(e);
+  }
 
   @Override
   public String toString() {

platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldRegionsTree.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2015 JetBrains s.r.o.
+ * Copyright 2000-2016 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.
@@ -358,6 +358,14 @@ abstract class FoldRegionsTree {
     return index < 0 ? null : myRegions.get(index);
   }
 
+  void clearDocumentRangesModificationStatus() {
+    for (FoldRegion region : myRegions) {
+      if (region instanceof FoldRegionImpl) {
+        ((FoldRegionImpl)region).resetDocumentRegionChanged();
+      }
+    }
+  }
+
   private class CachedData implements Cloneable {
     private final FoldRegion[] visibleRegions;
     private final FoldRegion[] topLevelRegions;

platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldingModelImpl.java

@@ -87,6 +87,18 @@ public class FoldingModelImpl implements FoldingModelEx, PrioritizedInternalDocu
     return (List<FoldRegion>)myGroups.get(group);
   }
 
+  @Override
+  public void clearDocumentRangesModificationStatus() {
+    assertIsDispatchThreadForEditor();
+    myFoldTree.clearDocumentRangesModificationStatus();
+  }
+
+  @Override
+  public boolean hasDocumentRegionChangedFor(@NotNull FoldRegion region) {
+    assertReadAccess();
+    return region instanceof FoldRegionImpl && ((FoldRegionImpl)region).hasDocumentRegionChanged();
+  }
+
   @NotNull
   public FoldRegion getFirstRegion(@NotNull FoldingGroup group, FoldRegion child) {
     final List<FoldRegion> regions = getGroupedRegions(group);