on demand xref generation does not produce Scopes (#1622) (#1631)

fixes #1622

Author: mrate

src/org/opensolaris/opengrok/analysis/plain/PlainAnalyzer.java

@@ -40,6 +40,7 @@
 import org.opensolaris.opengrok.configuration.Project;
 import org.opensolaris.opengrok.history.Annotation;
 import org.opensolaris.opengrok.search.QueryBuilder;
+import org.opensolaris.opengrok.util.NullWriter;
 
 /**
  * Analyzer for plain text files Created on September 21, 2005
@@ -89,6 +90,15 @@ public void analyze(Document doc, StreamSource src, Writer xrefOut) throws IOExc
                 doc.add(new StoredField(QueryBuilder.TAGS, tags));                
             }
         }
+        
+        if (scopesEnabled && xrefOut == null) {
+            /*
+             * Scopes are generated during xref generation. If xrefs are
+             * turned off we still need to run writeXref to produce scopes,
+             * we use a dummy writer that will throw away any xref output.
+             */
+            xrefOut = new NullWriter();
+        }
 
         if (xrefOut != null) {
             try (Reader in = getReader(src.getStream())) {

src/org/opensolaris/opengrok/util/NullWriter.java

@@ -0,0 +1,49 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * See LICENSE.txt included in this distribution for the specific
+ * language governing permissions and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at LICENSE.txt.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ */
+
+package org.opensolaris.opengrok.util;
+
+import java.io.IOException;
+import java.io.Writer;
+
+/**
+ * Implementation of Writer that doesn't produce any ouput. Serves as a dummy
+ * class where Writer is needed but the output is not relevant.
+ * 
+ * @author tkotal
+ */
+public class NullWriter extends Writer  {
+
+    @Override
+    public void write(char[] chars, int i, int i1) throws IOException {
+    }
+
+    @Override
+    public void flush() throws IOException {
+    }
+
+    @Override
+    public void close() throws IOException {
+    }
+    
+}