Fix bug where validation errors don't give any details

src/main/java/com/xmlcalabash/library/ValidateJing.java

@@ -105,7 +105,7 @@ public void run() throws SaxonApiException {
         boolean checkIdRefs = getOption(_dtd_id_idref_warnings,false);
         boolean dtdAugment  = getOption(_dtd_attribute_values,false);
 
-        ErrorHandler eh = new RNGErrorHandler();
+        RNGErrorHandler eh = new RNGErrorHandler();
         PropertyMapBuilder properties = new PropertyMapBuilder();
         properties.put(ValidateProperty.ERROR_HANDLER, eh);
         properties.put(ValidateProperty.URI_RESOLVER, runtime.getResolver());
@@ -156,15 +156,15 @@ public void run() throws SaxonApiException {
                 InputSource din = S9apiUtils.xdmToInputSource(runtime, doc);
                 if (!driver.validate(din)) {
                     if (assertValid) {
-                        throw XProcException.stepError(53);
+                        throw XProcException.stepError(53, eh.getErr());
                     }
                 }
             } else {
                 throw new XProcException(step.getNode(), "Error loading schema");
             }
         } catch (SAXParseException e) {
             if (assertValid) {
-                throw XProcException.stepError(53);
+                throw XProcException.stepError(53, e);
             }
         } catch (SAXException e) {
             throw new XProcException("SAX Exception", e);
@@ -188,6 +188,10 @@ private String compactSchema(XdmNode doc) {
     class RNGErrorHandler implements ErrorHandler {
         SAXParseException err = null;
 
+        public SAXParseException getErr() {
+            return err;
+        }
+
         public void fatalError(SAXParseException e) throws SAXException {
             error(e);
         }
@@ -213,7 +217,7 @@ public void error(SAXParseException e) throws SAXException {
             treeWriter.endDocument();
 
             step.reportError(treeWriter.getResult());
-            if (err != null) {
+            if (err == null) {
                 err = e;
             }
         }

src/main/java/com/xmlcalabash/library/ValidateWithRNG.java

@@ -59,7 +59,7 @@
     private WritablePipe result = null;
     private URI docBaseURI = null;
 
-    /* Creates a new instance of Delete */
+    /* Creates a new instance of ValidateWithRNG */
     public ValidateWithRNG(XProcRuntime runtime, XAtomicStep step) {
         super(runtime,step);
     }
@@ -102,7 +102,7 @@ public void run() throws SaxonApiException {
             doc = source.read();
             docBaseURI = doc.getBaseURI();
 
-            if (verifier != null && !verifier.verify(S9apiUtils.xdmToInputSource(runtime, doc))) {
+            if (!verifier.verify(S9apiUtils.xdmToInputSource(runtime, doc))) {
                 throw new XProcException(XProcException.err_E0001, "Document is not valid");
             }
 
@@ -113,7 +113,7 @@ public void run() throws SaxonApiException {
         } catch (SAXException sx) {
             // Assume the only error is validity failed?
             if (getOption(_assert_valid,false)) {
-                throw XProcException.stepError(53);
+                throw XProcException.stepError(53, sx);
             }
             result.write(doc);
         } catch (IOException ioe) {