[java, completion] IJPL-207762 DiamondInsertHandler is frontend friendly

GitOrigin-RevId: 0ce6ddcf00b66bc2ec7069d33ccd75c5c11072bb

java/java-frontback-impl/resource/intellij.java.frontback.impl.xml

@@ -78,5 +78,8 @@
     <registryKey key="java.formatter.chained.calls.pre212.compatibility"
                  defaultValue="false"
                  description="Format chained calls as in versions prior to 2021.2"/>
+
+    <completion.frontendFriendlyInsertHandler implementationClass="com.intellij.codeInsight.completion.method.DiamondInsertHandler"/>
+
   </extensions>
 </idea-plugin>

java/java-frontback-impl/src/com/intellij/codeInsight/completion/method/DiamondInsertHandler.kt

@@ -0,0 +1,16 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.codeInsight.completion.method
+
+import com.intellij.codeInsight.completion.FrontendFriendlyInsertHandler
+import com.intellij.codeInsight.completion.InsertionContext
+import com.intellij.codeInsight.lookup.LookupElement
+import kotlinx.serialization.Serializable
+import org.jetbrains.annotations.ApiStatus
+
+@ApiStatus.Internal
+@Serializable
+class DiamondInsertHandler : FrontendFriendlyInsertHandler {
+  override fun handleInsert(context: InsertionContext, item: LookupElement) {
+    context.document.insertString(context.tailOffset, "<>")
+  }
+}

java/java-impl/src/com/intellij/codeInsight/completion/JavaMethodCallInsertHandler.kt

@@ -69,7 +69,7 @@ public class JavaMethodCallInsertHandler(
    */
   private val myHandlers: List<InsertHandler<in JavaMethodCallElement>> = listOfNotNull(
     RefStartInsertHandler(),
-    DiamondInsertHandler(),
+    createDiamondInsertHandler(item),
     ParenthInsertHandler(),
     beforeHandler,
     ImportQualifyAndInsertTypeParametersHandler(needImportOrQualify, needExplicitTypeParameters),
@@ -178,12 +178,11 @@ private class RefStartInsertHandler : InsertHandler<LookupElement> {
   }
 }
 
-private class DiamondInsertHandler : InsertHandler<JavaMethodCallElement> {
-  override fun handleInsert(context: InsertionContext, item: JavaMethodCallElement) {
-    val method = item.getObject().takeIf { it.isConstructor } ?: return
-    if (method.containingClass?.typeParameters?.isNotEmpty() != true) return
-    context.document.insertString(context.tailOffset, "<>")
-  }
+private fun createDiamondInsertHandler(item: JavaMethodCallElement): InsertHandler<LookupElement>? {
+  val method = item.getObject().takeIf { it.isConstructor } ?: return null
+  val containingClass = method.containingClass ?: return null
+  if (containingClass.typeParameters.isEmpty()) return null
+  return DiamondInsertHandler()
 }
 
 private class ParenthInsertHandler : InsertHandler<JavaMethodCallElement> {