Fix Java navbar for file with multiple classes

GitOrigin-RevId: 81e4fc4106dd50198384815226d33ed0a850707d

java/java-impl/src/com/intellij/ide/navigationToolbar/JavaNavBarExtension.java

@@ -112,4 +112,12 @@ public class JavaNavBarExtension extends StructureAwareNavBarModelExtension {
   protected List<NodeProvider<?>> getApplicableNodeProviders() {
     return myNodeProviders;
   }
+
+  @Override
+  protected boolean acceptParentFromModel(@Nullable PsiElement psiElement) {
+    if (psiElement instanceof PsiJavaFile) {
+      return ((PsiJavaFile) psiElement).getClasses().length > 1;
+    }
+    return true;
+  }
 }

java/java-tests/testData/ide/navigationToolbar/multipleClasses.java

@@ -0,0 +1,7 @@
+public class Foo {
+
+}
+
+class Bar {
+  <caret>
+}

java/java-tests/testSrc/com/intellij/ide/navigationToolbar/JavaNavBarTest.java

@@ -32,6 +32,11 @@ public class JavaNavBarTest extends LightJavaCodeInsightFixtureTestCase {
     assertNavBarModel("src", "LambdaExpression", "foo", "Lambda");
   }
 
+  public void testMultipleClasses() {
+    myFixture.configureByFile("multipleClasses.java");
+    assertNavBarModel("src", "multipleClasses.java", "Bar");
+  }
+
   public void assertNavBarModel(String... expectedItems) {
     NavBarModel model = new NavBarModel(myFixture.getProject());
     model.updateModel(((EditorEx)myFixture.getEditor()).getDataContext());

platform/lang-impl/src/com/intellij/ide/navigationToolbar/StructureAwareNavBarModelExtension.kt

@@ -60,7 +60,7 @@ abstract class StructureAwareNavBarModelExtension : AbstractNavBarModelExtension
       val model = buildStructureViewModel(file)
       if (model != null) {
         val parentInModel = findParentInModel(model.root, psiElement)
-        if (parentInModel !is PsiFile) {
+        if (acceptParentFromModel(parentInModel)) {
           return parentInModel
         }
       }
@@ -68,6 +68,10 @@ abstract class StructureAwareNavBarModelExtension : AbstractNavBarModelExtension
     return super.getParent(psiElement)
   }
 
+  protected open fun acceptParentFromModel(psiElement: PsiElement?): Boolean {
+    return true
+  }
+
   private fun findParentInModel(root: StructureViewTreeElement, psiElement: PsiElement): PsiElement? {
     for (child in childrenFromNodeAndProviders(root)) {
       if ((child as StructureViewTreeElement).value == psiElement) {