From e5009c3dd2da712c03ee68173a8291d57c851057 Mon Sep 17 00:00:00 2001
From: shelches <42914500+shelches@users.noreply.github.com>
Date: Fri, 27 May 2022 17:59:43 -0500
Subject: [PATCH] Fix ClassCastException when using StringBuilder/Buffer #496
 (#1210)

Convert non-String, non-ConsString objects to a string when creating a ConsString so that StringBuilders and other CharSequence objects can be used natively more easily.

Fixes https://github.com/mozilla/rhino/discussions/1206 and https://github.com/mozilla/rhino/issues/496

Co-authored-by: Edward Jensen <edward.jensen@infor.com>
---
 src/org/mozilla/javascript/ConsString.java    |  6 +++
 .../javascript/tests/Issue1206Test.java       | 42 +++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 testsrc/org/mozilla/javascript/tests/Issue1206Test.java

diff --git a/src/org/mozilla/javascript/ConsString.java b/src/org/mozilla/javascript/ConsString.java
index 58c06eadbb..cd0d040293 100644
--- a/src/org/mozilla/javascript/ConsString.java
+++ b/src/org/mozilla/javascript/ConsString.java
@@ -34,6 +34,12 @@ public class ConsString implements CharSequence, Serializable, Wrapper {
     private boolean isFlat;
 
     public ConsString(CharSequence str1, CharSequence str2) {
+        if (!(str1 instanceof String) && !(str1 instanceof ConsString)) {
+            str1 = str1.toString();
+        }
+        if (!(str2 instanceof String) && !(str2 instanceof ConsString)) {
+            str2 = str2.toString();
+        }
         left = str1;
         right = str2;
         length = left.length() + right.length();
diff --git a/testsrc/org/mozilla/javascript/tests/Issue1206Test.java b/testsrc/org/mozilla/javascript/tests/Issue1206Test.java
new file mode 100644
index 0000000000..a4b0d548d2
--- /dev/null
+++ b/testsrc/org/mozilla/javascript/tests/Issue1206Test.java
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.javascript.tests;
+
+import junit.framework.TestCase;
+import org.junit.Test;
+import org.mozilla.javascript.Context;
+import org.mozilla.javascript.Scriptable;
+
+/**
+ * Tests the ConsString class to ensure it properly supports String, StringBuffer and StringBuilder.
+ */
+public class Issue1206Test extends TestCase {
+    @Test
+    public void testConsStringUsingString() {
+        Context cx = Context.enter();
+        Scriptable scope = cx.initStandardObjects(null);
+        scope.put("var1", scope, "hello");
+        Object result = cx.evaluateString(scope, "var1 = var1 + ' world'", "test", 1, null);
+        assertEquals("hello world", result);
+    }
+
+    @Test
+    public void testConsStringUsingStringBuffer() {
+        Context cx = Context.enter();
+        Scriptable scope = cx.initStandardObjects(null);
+        scope.put("var1", scope, new StringBuffer("hello"));
+        Object result = cx.evaluateString(scope, "var1 = var1 + ' world'", "test", 1, null);
+        assertEquals("hello world", result);
+    }
+
+    @Test
+    public void testConsStringUsingStringBuilder() {
+        Context cx = Context.enter();
+        Scriptable scope = cx.initStandardObjects(null);
+        scope.put("var1", scope, new StringBuilder("hello"));
+        Object result = cx.evaluateString(scope, "var1 = var1 + ' world'", "test", 1, null);
+        assertEquals("hello world", result);
+    }
+}