From 7f9ce8bbcf0275a713fa335f9a2c1ab43bc13b22 Mon Sep 17 00:00:00 2001
From: ghm <ghm@google.com>
Date: Mon, 20 Mar 2023 11:08:55 -0700
Subject: [PATCH] UnusedNestedClass: don't complain about classes whose name
 begins with "Unused".

PiperOrigin-RevId: 518021137
---
 .../errorprone/bugpatterns/UnusedNestedClass.java     |  5 ++++-
 .../errorprone/bugpatterns/UnusedNestedClassTest.java | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/UnusedNestedClass.java b/core/src/main/java/com/google/errorprone/bugpatterns/UnusedNestedClass.java
index 2981f111f92..57aebe9705d 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/UnusedNestedClass.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/UnusedNestedClass.java
@@ -16,6 +16,7 @@
 
 package com.google.errorprone.bugpatterns;
 
+import static com.google.common.base.Ascii.toLowerCase;
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
 import static com.google.errorprone.matchers.Description.NO_MATCH;
 import static com.google.errorprone.util.ASTHelpers.canBeRemoved;
@@ -91,7 +92,9 @@ public Void visitClass(ClassTree classTree, Void unused) {
     }
 
     private boolean ignoreUnusedClass(ClassTree classTree, VisitorState state) {
-      return isSuppressed(classTree, state) || shouldKeep(classTree);
+      return isSuppressed(classTree, state)
+          || shouldKeep(classTree)
+          || toLowerCase(classTree.getSimpleName().toString()).startsWith("unused");
     }
   }
 
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/UnusedNestedClassTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/UnusedNestedClassTest.java
index 003935411f8..f1143e555db 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/UnusedNestedClassTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/UnusedNestedClassTest.java
@@ -43,6 +43,17 @@ public void positive() {
         .doTest();
   }
 
+  @Test
+  public void exemptedByUnusedPrefix() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java", //
+            "class A {",
+            "  private class UnusedClass {}",
+            "}")
+        .doTest();
+  }
+
   @Test
   public void nonPrivateNestedClass_noWarning() {
     compilationHelper