From a9ccd926c2db12d4ec6d54e4fc8b18945b3f5197 Mon Sep 17 00:00:00 2001
From: duonglaiquang <duonglaiquang@gmail.com>
Date: Thu, 4 Jan 2024 14:09:33 +0900
Subject: [PATCH] NativeRegExp: fix RegExp.prototype.toString throwing
 TypeError on NativeObject

---
 src/org/mozilla/javascript/regexp/NativeRegExp.java    |  9 +++++++++
 .../org/mozilla/javascript/tests/NativeRegExpTest.java | 10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/org/mozilla/javascript/regexp/NativeRegExp.java b/src/org/mozilla/javascript/regexp/NativeRegExp.java
index 2b7cffdefe..50d7f55760 100644
--- a/src/org/mozilla/javascript/regexp/NativeRegExp.java
+++ b/src/org/mozilla/javascript/regexp/NativeRegExp.java
@@ -11,6 +11,7 @@
 import org.mozilla.javascript.IdFunctionObject;
 import org.mozilla.javascript.IdScriptableObject;
 import org.mozilla.javascript.Kit;
+import org.mozilla.javascript.NativeObject;
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
@@ -2716,6 +2717,14 @@ public Object execIdCall(
                 return realThis(thisObj, f).compile(cx, scope, args);
 
             case Id_toString:
+                if (thisObj instanceof NativeObject) {
+                    Object sourceObj = thisObj.get("source", thisObj);
+                    String source = sourceObj.equals(NOT_FOUND) ? "undefined" : escapeRegExp(sourceObj);
+                    Object flagsObj = thisObj.get("flags", thisObj);
+                    String flags = flagsObj.equals(NOT_FOUND) ? "undefined" : flagsObj.toString();
+
+                    return "/" + source + "/" + flags;
+                }
             case Id_toSource:
                 return realThis(thisObj, f).toString();
 
diff --git a/testsrc/org/mozilla/javascript/tests/NativeRegExpTest.java b/testsrc/org/mozilla/javascript/tests/NativeRegExpTest.java
index 944629438d..47d8da1481 100644
--- a/testsrc/org/mozilla/javascript/tests/NativeRegExpTest.java
+++ b/testsrc/org/mozilla/javascript/tests/NativeRegExpTest.java
@@ -328,6 +328,16 @@ public void flagsPropery() throws Exception {
         test("0-undefined-true-false-undefined", script);
     }
 
+    /** @throws Exception if an error occurs */
+    @Test
+    public void objectToString() throws Exception {
+        test("/undefined/undefined", "RegExp.prototype.toString.call({})");
+        test("/Foo/undefined", "RegExp.prototype.toString.call({source: 'Foo'})");
+        test("/undefined/gy", "RegExp.prototype.toString.call({flags: 'gy'})");
+        test("/Foo/g", "RegExp.prototype.toString.call({source: 'Foo', flags: 'g'})");
+        test("/Foo/g", "RegExp.prototype.toString.call({source: 'Foo', flags: 'g', sticky: true})");
+    }
+
     private static void test(final String expected, final String script) {
         Utils.runWithAllOptimizationLevels(
                 cx -> {