fix: report undefined entity references in EPUB 2.0.1

References to undeclared entities where skipped in EPUB 2.0.1 parsing
(due to using a non-validating parser).
The declaration handler is now registered as a content handler to check
for skipped entities and report unknown ones.

Fix #1546

src/main/java/com/adobe/epubcheck/xml/XMLParser.java

@@ -55,8 +55,6 @@
 public class XMLParser
 {
 
-  private static final String SAXPROP_LEXICAL_HANDLER = "http://xml.org/sax/properties/lexical-handler";
-  private static final String SAXPROP_DECL_HANDLER = "http://xml.org/sax/properties/declaration-handler";
   private final ValidationContext context;
   private final Report report;
   private final URL url;
@@ -76,9 +74,9 @@ public XMLParser(ValidationContext context)
     {
       factory.setNamespaceAware(true);
       factory.setValidating(false);
+      factory.setFeature("http://xml.org/sax/features/validation", false);
       factory.setFeature("http://xml.org/sax/features/external-general-entities", false);
       factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
-      factory.setFeature("http://xml.org/sax/features/validation", false);
       if (context.version == EPUBVersion.VERSION_3)
       {
         factory.setXIncludeAware(false);
@@ -93,9 +91,12 @@ public XMLParser(ValidationContext context)
       handler.setEntityResolver(new DefaultResolver(context.version));
 
       XMLReader reader = parser.getXMLReader();
-      DeclarationHandler docTypeHandler = new DeclarationHandler(context);
-      reader.setProperty(SAXPROP_LEXICAL_HANDLER, docTypeHandler);
-      reader.setProperty(SAXPROP_DECL_HANDLER, docTypeHandler);
+      DeclarationHandler docTypeHandler = new DeclarationHandler(context, parser);
+      reader.setProperty("http://xml.org/sax/properties/lexical-handler", docTypeHandler);
+      reader.setProperty("http://xml.org/sax/properties/declaration-handler", docTypeHandler);
+      // add the declaration handler as a content handler
+      // to check for skipped entities
+      handler.addContentHandler(docTypeHandler);
 
     } catch (Exception e)
     {

src/main/java/com/adobe/epubcheck/xml/handlers/DeclarationHandler.java

@@ -3,6 +3,10 @@
 import java.util.HashSet;
 import java.util.Set;
 
+import javax.xml.parsers.SAXParser;
+
+import org.apache.xerces.impl.XMLErrorReporter;
+import org.apache.xerces.impl.msg.XMLMessageFormatter;
 import org.xml.sax.SAXException;
 
 import com.adobe.epubcheck.api.Report;
@@ -18,13 +22,15 @@ public class DeclarationHandler extends LocationHandler
   private final EPUBVersion version;
   private boolean firstStartDTDInvocation = true;
   private final Set<String> entities = new HashSet<String>();
+  private final SAXParser parser;
 
-  public DeclarationHandler(ValidationContext context)
+  public DeclarationHandler(ValidationContext context, SAXParser parser)
   {
     super(context);
     this.report = context.report;
     this.mimeType = context.mimeType;
     this.version = context.version;
+    this.parser = parser;
 
     // XML predefined
     entities.add("gt");
@@ -191,4 +197,32 @@ public void internalEntityDecl(String name, String value)
   {
     entities.add(name);
   }
+
+  @Override
+  public void skippedEntity(String name)
+    throws SAXException
+  {
+    if (!name.startsWith("%") && !name.equals("[dtd]"))
+    {
+      // A non-validating parser with an external subset with
+      // skip any unknown entity reference.
+      // This is the case in EPUB 2.0.1 content documents.
+      // We check if the entity was declared and report an
+      // error if not.
+      if (!entities.contains("name"))
+      {
+        // We use the Xerces XNI error reporter to make
+        // the reporting message consistent with what Xerces
+        // would report itself.
+        XMLErrorReporter xniReporter = (XMLErrorReporter) parser
+            .getProperty("http://apache.org/xml/properties/internal/error-reporter");
+        xniReporter.reportError(XMLMessageFormatter.XML_DOMAIN,
+            "EntityNotDeclared",
+            new Object[] { name },
+            XMLErrorReporter.SEVERITY_FATAL_ERROR);
+      }
+    }
+  }
+
+
 }

src/test/resources/epub2/files/ops-document-xhtml/entities-unknown-error.xhtml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
+	<head>
+        <title>Test</title>
+	</head>
+	<body>
+		<h1>Loomings</h1>
+        <!-- this entity reference uses an unknown entity name -->
+        &foo; 
+	</body>
+</html>

src/test/resources/epub2/ops-content-document-xhtml.feature

@@ -49,6 +49,12 @@ Feature: EPUB 2 ▸ Open Publication Structure ▸ XHTML Document Checks
     When checking document 'entities-character-references-valid.xhtml'
     Then no errors or warnings are reported
 
+  Scenario: Report unknown entity references
+    When checking document 'entities-unknown-error.xhtml'
+    Then fatal error RSC-016 is reported
+    And the message contains 'was referenced, but not declared'
+    And no other errors or warnings are reported
+
   Scenario: Report HTML5 elements used in OPS XHTML Content Documents
     When checking document 'html5-elements-error.xhtml'
     Then error RSC-005 is reported

src/test/resources/epub3/06-content-document/files/entities-external-error.xhtml

@@ -7,6 +7,5 @@
         <title>Entites declared in the internal subset are allowed</title>
     </head>
     <body>
-        &foo; 
     </body>
 </html>