fix issue #648

src/org/mozilla/javascript/regexp/RegExpImpl.java

@@ -113,6 +113,7 @@ public Object action(Context cx, Scriptable scope,
                     int index = str.indexOf(search);
                     if (index >= 0) {
                         int slen = search.length();
+                        this.parens = null;
                         this.lastParen = null;
                         this.leftContext = new SubString(str, 0, index);
                         this.lastMatch = new SubString(str, index, slen);
@@ -756,8 +757,7 @@ private static int find_split(Context cx, Scriptable scope, String target,
 
     protected String          input;         /* input string to match (perl $_, GC root) */
     protected boolean         multiline;     /* whether input contains newlines (perl $*) */
-    protected SubString[]     parens;        /* Vector of SubString; last set of parens
-                                      matched (perl $1, $2) */
+    protected SubString[]     parens;        /* Vector of SubString; last set of parens matched (perl $1, $2) */
     protected SubString       lastMatch;     /* last string matched (perl $&) */
     protected SubString       lastParen;     /* last paren matched (perl $+) */
     protected SubString       leftContext;   /* input to left of last match (perl $`) */

testsrc/org/mozilla/javascript/tests/es5/RegexpTest.java

@@ -0,0 +1,49 @@
+/* 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/. */
+
+/*
+ * Tests for the Object.getOwnPropertyDescriptor(obj, prop) method
+ */
+package org.mozilla.javascript.tests.es5;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.mozilla.javascript.Context;
+import org.mozilla.javascript.ScriptableObject;
+
+public class RegexpTest {
+
+    private Context cx;
+    private ScriptableObject scope;
+
+    @Before
+    public void setUp() {
+        cx = Context.enter();
+        cx.setLanguageVersion(Context.VERSION_1_8);
+        scope = cx.initStandardObjects();
+    }
+
+    @After
+    public void tearDown() {
+        Context.exit();
+    }
+
+    /**
+     * see https://github.com/mozilla/rhino/issues/684.
+     */
+    @Test
+    public void testSideEffect() {
+        Object result2 = cx.evaluateString(
+                scope, "var a = 'hello world';"
+                        + "a.replace(/(.)/g, '#');"
+                        + "var res = '';"
+                        + "a.replace([], function (b, c) { res += c; });"
+                        + "res;",
+                "test", 1, null
+        );
+        assertEquals("0", result2);
+    }
+}