From dbf4ef48439bb039d97f1ac5918927dab7dfd2e3 Mon Sep 17 00:00:00 2001
From: Ronald Brill <rbri@rbri.de>
Date: Sun, 10 Nov 2024 12:41:34 +0100
Subject: [PATCH] StyleSheetList.item() should return null if the provided
 index is not available

---
 src/changes/changes.xml                       |  3 +
 .../javascript/host/css/StyleSheetList.java   | 28 ++++----
 .../host/html/HTMLTableElement.java           |  2 +-
 .../host/css/StyleSheetListTest.java          | 64 +++++++++++++++++++
 4 files changed, 84 insertions(+), 13 deletions(-)

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index b942b04842f..94b5fb1d2db 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -11,6 +11,9 @@
             <action type="fix" dev="rbri">
                 Javadoc fixed for Document.elementFromPoint().
             </action>
+            <action type="fix" dev="rbri">
+                StyleSheetList.item() should return null if the provided index is not available.
+            </action>
             <action type="fix" dev="rbri">
                 HTMLOptionsCollection.item() should return null if the provided index is not available.
             </action>
diff --git a/src/main/java/org/htmlunit/javascript/host/css/StyleSheetList.java b/src/main/java/org/htmlunit/javascript/host/css/StyleSheetList.java
index f67a7a2b033..333dafbe33c 100644
--- a/src/main/java/org/htmlunit/javascript/host/css/StyleSheetList.java
+++ b/src/main/java/org/htmlunit/javascript/host/css/StyleSheetList.java
@@ -136,18 +136,11 @@ public int getLength() {
      */
     @JsxFunction
     public Object item(final int index) {
-        if (nodes_ == null || index < 0 || index >= nodes_.getLength()) {
-            return JavaScriptEngine.UNDEFINED;
+        final Object item = get(index, this);
+        if (JavaScriptEngine.UNDEFINED == item) {
+            return null;
         }
-
-        final HTMLElement element = (HTMLElement) nodes_.item(Integer.valueOf(index));
-
-        // <style type="text/css"> ... </style>
-        if (element instanceof HTMLStyleElement) {
-            return ((HTMLStyleElement) element).getSheet();
-        }
-        // <link rel="stylesheet" type="text/css" href="..." />
-        return ((HTMLLinkElement) element).getSheet();
+        return item;
     }
 
     /**
@@ -156,7 +149,18 @@ public Object item(final int index) {
     @Override
     public Object get(final int index, final Scriptable start) {
         if (this == start) {
-            return item(index);
+            if (nodes_ == null || index < 0 || index >= nodes_.getLength()) {
+                return JavaScriptEngine.UNDEFINED;
+            }
+
+            final HTMLElement element = (HTMLElement) nodes_.item(Integer.valueOf(index));
+
+            // <style type="text/css"> ... </style>
+            if (element instanceof HTMLStyleElement) {
+                return ((HTMLStyleElement) element).getSheet();
+            }
+            // <link rel="stylesheet" type="text/css" href="..." />
+            return ((HTMLLinkElement) element).getSheet();
         }
         return super.get(index, start);
     }
diff --git a/src/main/java/org/htmlunit/javascript/host/html/HTMLTableElement.java b/src/main/java/org/htmlunit/javascript/host/html/HTMLTableElement.java
index 2f4f432d2d3..b7a3a20d0f9 100644
--- a/src/main/java/org/htmlunit/javascript/host/html/HTMLTableElement.java
+++ b/src/main/java/org/htmlunit/javascript/host/html/HTMLTableElement.java
@@ -264,7 +264,7 @@ protected boolean isContainedRow(final HtmlTableRow row) {
      * {@inheritDoc}
      */
     @Override
-    public Object insertRow(final int index) {
+    public HtmlUnitScriptable insertRow(final int index) {
         // check if a tbody should be created
         if (index != 0) {
             for (final HtmlElement htmlElement : getDomNodeOrDie().getHtmlElementDescendants()) {
diff --git a/src/test/java/org/htmlunit/javascript/host/css/StyleSheetListTest.java b/src/test/java/org/htmlunit/javascript/host/css/StyleSheetListTest.java
index 94b7379721d..d2765f774e0 100644
--- a/src/test/java/org/htmlunit/javascript/host/css/StyleSheetListTest.java
+++ b/src/test/java/org/htmlunit/javascript/host/css/StyleSheetListTest.java
@@ -308,6 +308,70 @@ public void in() throws Exception {
         loadPageVerifyTitle2(html);
     }
 
+
+    /**
+     * @throws Exception if an error occurs
+     */
+    @Test
+    @Alerts({"1", "undefined", "[object CSSStyleSheet]", "undefined", "undefined"})
+    public void index() throws Exception {
+        final String html =
+              "<html>\n"
+            + "  <head>\n"
+            + "    <link rel='stylesheet' type='text/css' href='foo.css'/>\n"
+            + "    <script>\n"
+            + LOG_TITLE_FUNCTION
+            + "      function test() {\n"
+            + "        var sheets = document.styleSheets;\n"
+            + "        log(sheets.length);\n"
+            + "        log(sheets[-1]);\n"
+            + "        log(sheets[0]);\n"
+            + "        log(sheets[1]);\n"
+            + "        log(sheets[42]);\n"
+            + "      }\n"
+            + "    </script>\n"
+            + "  </head>\n"
+            + "  <body onload='test()'>abc</body>\n"
+            + "</html>";
+
+        final String css = "div {color:red}";
+        getMockWebConnection().setDefaultResponse(css, MimeType.TEXT_CSS);
+
+        loadPageVerifyTitle2(html);
+    }
+
+
+    /**
+     * @throws Exception if an error occurs
+     */
+    @Test
+    @Alerts({"1", "null", "[object CSSStyleSheet]", "null", "null"})
+    public void item() throws Exception {
+        final String html =
+              "<html>\n"
+            + "  <head>\n"
+            + "    <link rel='stylesheet' type='text/css' href='foo.css'/>\n"
+            + "    <script>\n"
+            + LOG_TITLE_FUNCTION
+            + "      function test() {\n"
+            + "        var sheets = document.styleSheets;\n"
+            + "        log(sheets.length);\n"
+            + "        log(sheets.item(-1));\n"
+            + "        log(sheets.item(0));\n"
+            + "        log(sheets.item(1));\n"
+            + "        log(sheets.item(42));\n"
+            + "      }\n"
+            + "    </script>\n"
+            + "  </head>\n"
+            + "  <body onload='test()'>abc</body>\n"
+            + "</html>";
+
+        final String css = "div {color:red}";
+        getMockWebConnection().setDefaultResponse(css, MimeType.TEXT_CSS);
+
+        loadPageVerifyTitle2(html);
+    }
+
     /**
      * @throws Exception if an error occurs
      */