Add XML-specific read capabilities support, test

src/main/java/com/fasterxml/jackson/dataformat/xml/deser/FromXmlParser.java

@@ -14,6 +14,8 @@
 import com.fasterxml.jackson.core.base.ParserMinimalBase;
 import com.fasterxml.jackson.core.io.IOContext;
 import com.fasterxml.jackson.core.util.ByteArrayBuilder;
+import com.fasterxml.jackson.core.util.JacksonFeatureSet;
+
 import com.fasterxml.jackson.dataformat.xml.PackageVersion;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.fasterxml.jackson.dataformat.xml.util.CaseInsensitiveNameSet;
@@ -32,6 +34,15 @@ public class FromXmlParser
      */
     public final static String DEFAULT_UNNAMED_TEXT_PROPERTY = "";
 
+    /**
+     * XML format has some peculiarities, indicated via new (2.12) capability
+     * system.
+     *
+     * @since 2.12
+     */
+    public JacksonFeatureSet<StreamReadCapability> XML_READ_CAPABILITIES =
+            DEFAULT_READ_CAPABILITIES.with(StreamReadCapability.DUPLICATE_PROPERTIES);
+
     /**
      * Enumeration that defines all togglable features for XML parsers.
      */
@@ -217,7 +228,13 @@ public void setCodec(ObjectCodec c) {
     public void setXMLTextElementName(String name) {
         _cfgNameForTextElement = name;
     }
-
+
+    /*
+    /**********************************************************************
+    /* Overrides: capability introspection methods
+    /**********************************************************************
+     */
+
     /**
      * XML format does require support from custom {@link ObjectCodec}
      * (that is, {@link XmlMapper}), so need to return true here.
@@ -228,7 +245,18 @@ public void setXMLTextElementName(String name) {
     public boolean requiresCustomCodec() {
         return true;
     }
-
+
+    @Override
+    public boolean canReadObjectId() { return false; }
+
+    @Override
+    public boolean canReadTypeId() { return false; }
+
+    @Override
+    public JacksonFeatureSet<StreamReadCapability> getReadCapabilities() {
+        return XML_READ_CAPABILITIES;
+    }
+
     /*
     /**********************************************************
     /* Extended API, configuration

src/test/java/com/fasterxml/jackson/dataformat/xml/stream/StreamCapabilitiesTest.java

@@ -0,0 +1,18 @@
+package com.fasterxml.jackson.dataformat.xml.stream;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.StreamReadCapability;
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
+
+public class StreamCapabilitiesTest extends XmlTestBase
+{
+    private final XmlMapper MAPPER = newMapper();
+
+    public void testReadCapabilities() throws Exception
+    {
+        try (JsonParser p = MAPPER.createParser("<root />")) {
+            assertTrue(p.getReadCapabilities().isEnabled(StreamReadCapability.DUPLICATE_PROPERTIES));
+        }
+    }
+}