IDEA-64687 Impossible to add an import statement when import section is collapsed

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

@@ -15,8 +15,10 @@
  */
 package com.intellij.codeInsight.folding;
 
-import com.intellij.openapi.application.ex.PathManagerEx;
-import com.intellij.testFramework.fixtures.CodeInsightFixtureTestCase;
+
+import com.intellij.codeInsight.folding.impl.CodeFoldingManagerImpl
+import com.intellij.openapi.application.ex.PathManagerEx
+import com.intellij.testFramework.fixtures.CodeInsightFixtureTestCase
 
 /**
  * @author Denis Zhdanov
@@ -25,12 +27,26 @@ import com.intellij.testFramework.fixtures.CodeInsightFixtureTestCase;
 public class JavaFoldingTest extends CodeInsightFixtureTestCase {
   
   public void testEndOfLineComments() {
-    doTest();
+    myFixture.testFolding("$PathManagerEx.testDataPath/codeInsight/folding/${getTestName(false)}.java");
   }
-  
-  private void doTest() {
-    StringBuilder path = new StringBuilder(PathManagerEx.getTestDataPath()).append("/codeInsight/folding/")
-      .append(getTestName(false)).append(".java");
-    myFixture.testFolding(path.toString());
+
+  public void testEditingImports() {
+    myFixture.configureByText "a.java", """\
+import java.util.List;
+import java.util.Map;
+<caret>
+
+class Foo { List a; Map b; }
+"""
+
+    CodeFoldingManagerImpl.getInstance(getProject()).buildInitialFoldings(myFixture.editor);
+    myFixture.doHighlighting()
+    assert myFixture.editor.foldingModel.getCollapsedRegionAtOffset(10)
+
+    myFixture.type 'import '
+    myFixture.doHighlighting()
+    assert !myFixture.editor.foldingModel.getCollapsedRegionAtOffset(10)
   }
+
+
 }

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

@@ -18,6 +18,7 @@ package com.intellij.codeInsight.folding.impl;
 
 import com.intellij.lang.folding.FoldingDescriptor;
 import com.intellij.lang.injection.InjectedLanguageManager;
+import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.FoldRegion;
 import com.intellij.openapi.editor.FoldingGroup;
@@ -124,7 +125,12 @@ class UpdateFoldRegionsOperation implements Runnable {
   }
 
   private boolean shouldExpandNewRegion(PsiElement element, TextRange range, Map<TextRange, Boolean> rangeToExpandStatusMap) {
-    boolean caretInside = FoldingUtil.caretInsideRange(myEditor, range);
+    final Document document = myEditor.getDocument();
+    final int firstLine = document.getLineNumber(range.getStartOffset());
+    final int lastLine = document.getLineNumber(range.getEndOffset());
+    final int currentLine = document.getLineNumber(myEditor.getCaretModel().getOffset());
+    boolean caretInside = firstLine <= currentLine && currentLine <= lastLine;
+
     if (myApplyDefaultState) {
       return caretInside || !FoldingPolicy.isCollapseByDefault(element);
     }