Kotlin UI DSL: strict validation for LABEL_FOR and tests

GitOrigin-RevId: c72e012696aab5fc8ff834a140d9c0bf89d55d2c

platform/platform-impl/src/com/intellij/ui/dsl/builder/impl/utils.kt

@@ -155,8 +155,15 @@ private fun getLabelComponentFor(cell: CellBaseImpl<*>?): JComponent? {
 }
 
 private fun getLabelComponentFor(component: JComponent): JComponent? {
-  val delegate = component.getClientProperty(DslComponentProperty.LABEL_FOR) as? JComponent
-  if (delegate != null && delegate !== component) return getLabelComponentFor(delegate)
+  val labelFor = component.getClientProperty(DslComponentProperty.LABEL_FOR)
+  if (labelFor != null) {
+    if (labelFor is JComponent) {
+      return labelFor
+    }
+    else {
+      throw UiDslException("LABEL_FOR must be a JComponent: ${labelFor::class.java.name}")
+    }
+  }
 
   if (ALLOWED_LABEL_COMPONENTS.any { clazz -> clazz.isInstance(component) }) {
     return component
@@ -164,7 +171,6 @@ private fun getLabelComponentFor(component: JComponent): JComponent? {
   return null
 }
 
-
 internal fun warn(message: String) {
   if (FAIL_ON_WARN) {
     throw UiDslException(message)

platform/platform-tests/testSrc/com/intellij/ui/dsl/builder/LabelTest.kt

@@ -0,0 +1,59 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.ui.dsl.builder
+
+import com.intellij.ui.dsl.UiDslException
+import org.junit.Test
+import org.junit.jupiter.api.assertThrows
+import java.awt.TextArea
+import javax.swing.JLabel
+import javax.swing.JPanel
+import javax.swing.JTextField
+import kotlin.test.assertEquals
+
+class LabelTest {
+
+  @Test
+  fun testLabelFor() {
+    val label = JLabel("Label:")
+    lateinit var component: JTextField
+    panel {
+      row(label) {
+        component = textField().component
+      }
+    }
+
+    assertEquals(label.labelFor, component)
+  }
+
+  @Test
+  fun testLabelForProperty() {
+    val label = JLabel("Label:")
+    val panel = JPanel()
+    val textField = JTextField()
+    panel.add(textField)
+    panel.putClientProperty(DslComponentProperty.LABEL_FOR, textField)
+    panel {
+      row(label) {
+        cell(panel)
+      }
+    }
+
+    assertEquals(label.labelFor, textField)
+  }
+
+  @Test
+  fun testInvalidLabelForProperty() {
+    val label = JLabel("Label:")
+    val panel = JPanel()
+    val component = TextArea()
+    panel.add(component)
+    panel.putClientProperty(DslComponentProperty.LABEL_FOR, component)
+    assertThrows<UiDslException> {
+      panel {
+        row(label) {
+          cell(panel)
+        }
+      }
+    }
+  }
+}