[jsp] Update grammar to accept boolean attributes

pmd-jsp/etc/grammar/JspParser.jjt

@@ -1,4 +1,8 @@
-/* 
+/*
+ * Allow boolean attributes
+ *
+ * Juan Martín Sotuyo Dodero 06/2017
+ *====================================================================
  * Added capability for Tracking Tokens.
  *
  * Amit Kumar Prasad 10/2015
@@ -580,7 +584,7 @@ void Attribute() :
   (
   	<ATTR_EQ> 
   	AttributeValue()
-  )
+  )?
 }
 
 /**

pmd-jsp/src/test/java/net/sourceforge/pmd/lang/jsp/JspParserTest.java

@@ -29,6 +29,16 @@ public class JspParserTest {
                 "<span class=\"CostUnit\">$</span><span class=\"CostMain\">129</span><span class=\"CostFrac\">.00</span>");
         Assert.assertNotNull(node);
     }
+    
+    /**
+     * Verifies bug #311 Jsp parser fails on boolean attribute
+     */
+    @Test
+    public void testParseBooleanAttribute() {
+        Node node = parse(
+                "<label><input type='checkbox' checked name=cheese disabled=''> Cheese</label>");
+        Assert.assertNotNull(node);
+    }
 
     private Node parse(String code) {
         LanguageVersionHandler jspLang = LanguageRegistry.getLanguage(JspLanguageModule.NAME).getDefaultVersion()