From 90af13819d8b904f8d3d2b2e01359ed9ae1a910f Mon Sep 17 00:00:00 2001
From: Anton Kozub <anton.kozub@jetbrains.com>
Date: Sun, 29 Jun 2025 15:33:33 +0200
Subject: [PATCH] IDEA-375192 Structure View: Show empty node for lazy groups

GitOrigin-RevId: 3ec96a6ad7fa9b3416c299e31499f42c0a41436e
---
 .../messages/StructureViewBundle.properties    |  1 +
 .../logical/impl/LogicalStructureViewModel.kt  | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/platform/structure-view-impl/resources/messages/StructureViewBundle.properties b/platform/structure-view-impl/resources/messages/StructureViewBundle.properties
index 5d490f90065e..ad1b3fdfb3fe 100644
--- a/platform/structure-view-impl/resources/messages/StructureViewBundle.properties
+++ b/platform/structure-view-impl/resources/messages/StructureViewBundle.properties
@@ -5,6 +5,7 @@ action.structureview.show.inherited=Inherited
 action.structureview.sort.by.visibility=By Visibility
 file.structure.toggle.show.inherited=Inherited members
 node.structureview.invalid=<invalid>
+node.structureview.empty=<empty>
 structureview.subgroup.sort=Sort
 structureview.subgroup.filter=Show
 structureview.subgroup.group=Group
diff --git a/platform/structure-view-impl/src/com/intellij/ide/structureView/logical/impl/LogicalStructureViewModel.kt b/platform/structure-view-impl/src/com/intellij/ide/structureView/logical/impl/LogicalStructureViewModel.kt
index 9239c333913f..47b3cd9e78b1 100644
--- a/platform/structure-view-impl/src/com/intellij/ide/structureView/logical/impl/LogicalStructureViewModel.kt
+++ b/platform/structure-view-impl/src/com/intellij/ide/structureView/logical/impl/LogicalStructureViewModel.kt
@@ -4,6 +4,7 @@ package com.intellij.ide.structureView.logical.impl
 import com.intellij.ide.TypePresentationService
 import com.intellij.ide.projectView.PresentationData
 import com.intellij.ide.structureView.*
+import com.intellij.ide.structureView.StructureViewBundle
 import com.intellij.ide.structureView.impl.common.PsiTreeElementBase
 import com.intellij.ide.structureView.logical.ContainerElementsProvider
 import com.intellij.ide.structureView.logical.ExternalElementsProvider
@@ -37,7 +38,7 @@ class LogicalStructureViewModel private constructor(psiFile: PsiFile, editor: Ed
   }
 
   override fun isAlwaysLeaf(element: StructureViewTreeElement?): Boolean {
-    return element is ElementsBuilder.PropertyStructureElement
+    return element is ElementsBuilder.PropertyStructureElement || element is ElementsBuilder.EmptyChildrenElement
   }
 
   override fun isAutoExpand(element: StructureViewTreeElement): Boolean {
@@ -289,7 +290,9 @@ private class ElementsBuilder {
   ) : LogicalStructureViewTreeElement<T> {
 
     private val cashedChildren: Array<TreeElement> by lazy {
-      calculateChildren()
+      val result = calculateChildren()
+      if (result.isEmpty()) return@lazy arrayOf(EmptyChildrenElement())
+      result
     }
 
     override fun getValue(): Any = grouper
@@ -388,4 +391,15 @@ private class ElementsBuilder {
       return assembledModel.hashCode()
     }
   }
+
+  class EmptyChildrenElement: StructureViewTreeElement {
+    override fun getPresentation(): ItemPresentation {
+      return PresentationData(null, null, null, null).apply {
+        this.addText(StructureViewBundle.message("node.structureview.empty"), SimpleTextAttributes.GRAY_SMALL_ATTRIBUTES)
+      }
+    }
+
+    override fun getChildren(): Array<out TreeElement?> = emptyArray()
+    override fun getValue(): Any? = Any()
+  }
 }
\ No newline at end of file