From 1317b5529ca1435fc3f3ecb89b32f8fc237975a5 Mon Sep 17 00:00:00 2001
From: Simon Steiner <ssteiner@apache.org>
Date: Thu, 8 Dec 2022 13:04:53 +0000
Subject: [PATCH] FOP-3110: NPE if link destination is missing with
 accessibility

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1905858 13f79535-47bb-0310-9956-ffa450edef68
---
 .../fop/render/intermediate/IFSerializer.java |  7 ++-
 .../fop/intermediate/AbstractIFTest.java      | 21 +++++++-
 ...basic-link_internal-desination-missing.xml | 52 +++++++++++++++++++
 3 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 fop/test/intermediate/basic-link_internal-desination-missing.xml

diff --git a/fop-core/src/main/java/org/apache/fop/render/intermediate/IFSerializer.java b/fop-core/src/main/java/org/apache/fop/render/intermediate/IFSerializer.java
index ee6557d43..0bdcb0626 100644
--- a/fop-core/src/main/java/org/apache/fop/render/intermediate/IFSerializer.java
+++ b/fop-core/src/main/java/org/apache/fop/render/intermediate/IFSerializer.java
@@ -914,8 +914,11 @@ implements IFConstants, IFPainter, IFDocumentNavigationHandler {
         atts.addAttribute("", "rect", "rect",
                 XMLConstants.CDATA, IFUtil.toString(link.getTargetRect()));
         if (getUserAgent().isAccessibilityEnabled()) {
-            addStructRefAttribute(atts,
-                    ((IFStructureTreeElement) link.getAction().getStructureTreeElement()).getId());
+            IFStructureTreeElement structureTreeElement =
+                    (IFStructureTreeElement) link.getAction().getStructureTreeElement();
+            if (structureTreeElement != null) {
+                addStructRefAttribute(atts, structureTreeElement.getId());
+            }
         }
         try {
             handler.startElement(DocumentNavigationExtensionConstants.LINK, atts);
diff --git a/fop-core/src/test/java/org/apache/fop/intermediate/AbstractIFTest.java b/fop-core/src/test/java/org/apache/fop/intermediate/AbstractIFTest.java
index 48c3f335b..9e412a272 100644
--- a/fop-core/src/test/java/org/apache/fop/intermediate/AbstractIFTest.java
+++ b/fop-core/src/test/java/org/apache/fop/intermediate/AbstractIFTest.java
@@ -32,6 +32,10 @@ import javax.xml.transform.sax.SAXResult;
 import javax.xml.validation.Schema;
 import javax.xml.validation.SchemaFactory;
 import javax.xml.validation.Validator;
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathExpressionException;
+import javax.xml.xpath.XPathFactory;
 
 import org.w3c.dom.Document;
 import org.xml.sax.ErrorHandler;
@@ -105,6 +109,7 @@ abstract class AbstractIFTest extends AbstractIntermediateTest {
         DOMResult domResult = new DOMResult();
 
         FOUserAgent userAgent = createUserAgent();
+        userAgent.setAccessibility(isAccessibility(testDoc));
 
         //Create an instance of the target renderer so the XMLRenderer can use its font setup
         IFDocumentHandler targetHandler = userAgent.getRendererFactory().createDocumentHandler(
@@ -124,9 +129,23 @@ abstract class AbstractIFTest extends AbstractIntermediateTest {
         return (Document) domResult.getNode();
     }
 
+    private boolean isAccessibility(Document testDoc) {
+        try {
+            String s = eval(testDoc, "/testcase/cfg/accessibility");
+            return "true".equals(s);
+        } catch (XPathExpressionException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private String eval(Document doc, String xpath) throws XPathExpressionException {
+        XPath xPath = XPathFactory.newInstance().newXPath();
+        return (String) xPath.compile(xpath).evaluate(doc, XPathConstants.STRING);
+    }
+
     @Override
     protected void validate(Document doc) throws SAXException, IOException {
-        if (IF_SCHEMA == null) {
+        if (IF_SCHEMA == null || isAccessibility(testDoc)) {
             return; //skip validation;
         }
         Validator validator = IF_SCHEMA.newValidator();
diff --git a/fop/test/intermediate/basic-link_internal-desination-missing.xml b/fop/test/intermediate/basic-link_internal-desination-missing.xml
new file mode 100644
index 000000000..7b089037b
--- /dev/null
+++ b/fop/test/intermediate/basic-link_internal-desination-missing.xml
@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+<!-- $Id$ -->
+<testcase>
+  <info>
+    <p>
+      This test checks a fo:basic-link in a span
+    </p>
+  </info>
+  <cfg>
+    <accessibility>true</accessibility>
+  </cfg>  
+  <fo>
+    <fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format" xmlns:fox="http://xmlgraphics.apache.org/fop/extensions">
+      <fo:layout-master-set>
+        <fo:simple-page-master margin-top="0.3in" master-name="MBABase" page-width="8.5in" page-height="11in">
+          <fo:region-body region-name="LetterBody"/>
+        </fo:simple-page-master>
+        <fo:page-sequence-master master-name="MBALetterPages">
+          <fo:repeatable-page-master-alternatives>
+            <fo:conditional-page-master-reference master-reference="MBABase"/>
+          </fo:repeatable-page-master-alternatives>
+        </fo:page-sequence-master>
+      </fo:layout-master-set>
+      <fo:page-sequence format="1" id="th_default_sequence5" initial-page-number="auto" master-reference="MBALetterPages">
+        <fo:flow flow-name="LetterBody">
+          <fo:block>
+            <fo:basic-link internal-destination="Section1">SECTION 1 Introduction</fo:basic-link>
+          </fo:block>
+        </fo:flow>
+      </fo:page-sequence>
+    </fo:root>
+  </fo>
+  <if-checks xmlns:nav="http://xmlgraphics.apache.org/fop/intermediate/document-navigation">
+    <eval expected="-1" xpath="//nav:link/nav:goto-xy/@page-index"/>
+  </if-checks>
+</testcase>
-- 
2.39.5