if economy mode is on and history off, generate xref on the fly

fixes #2316

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/web/PageConfig.java

@@ -1221,7 +1221,7 @@ public File findDataFile() {
                 path, env.isCompressXref());
     }
 
-    protected String getLatestRevision() {
+    public String getLatestRevision() {
         if (!getEnv().isHistoryEnabled()) {
             return null;
         }
@@ -1265,15 +1265,14 @@ public boolean isLatestRevision(String rev) {
     }
 
     /**
-     * Get the location of cross reference for given file containing the current
-     * revision.
-     * @return location to redirect to or null if failed
+     * Get the location of cross reference for given file containing the given revision.
+     * @param revStr revision string
+     * @return location to redirect to or null if revision string is empty
      */
-    public String getLatestRevisionLocation() {
+    public String getRevisionLocation(String revStr) {
         StringBuilder sb = new StringBuilder();
-        String revStr;
 
-        if ((revStr = getLatestRevision()) == null) {
+        if (revStr == null) {
             return null;
         }
 

opengrok-indexer/src/test/java/org/opengrok/indexer/web/PageConfigTest.java

@@ -270,7 +270,7 @@ public String getPathInfo() {
         String rev = cfg.getLatestRevision();
         assertNull(rev);
 
-        String location = cfg.getLatestRevisionLocation();
+        String location = cfg.getRevisionLocation(cfg.getLatestRevision());
         assertNull(location);
     }
 

opengrok-web/src/main/webapp/list.jsp

@@ -88,6 +88,7 @@ document.pageReady.push(function() { pageReadyList();});
     PageConfig cfg = PageConfig.get(request);
     String rev = cfg.getRequestedRevision();
     Project project = cfg.getProject();
+    final String DUMMY_REVISION = "dummy";
 
     String navigateWindowEnabled = project != null ? Boolean.toString(
             project.isNavigateWindowEnabled()) : "false";
@@ -251,8 +252,12 @@ Click <a href="<%= rawPath %>">download <%= basename %></a><%
             if (g == Genre.PLAIN || g == Genre.HTML || g == null) {
                 InputStream in = null;
                 try {
-                    in = HistoryGuru.getInstance()
-                        .getRevision(resourceFile.getParent(), basename, rev);
+                    if (rev.equals(DUMMY_REVISION)) {
+                        in = new FileInputStream(resourceFile);
+                    } else {
+                        in = HistoryGuru.getInstance()
+                                .getRevision(resourceFile.getParent(), basename, rev);
+                    }
                 } catch (Exception e) {
                     // fall through to error message
                     error = e.getMessage();
@@ -344,13 +349,21 @@ Click <a href="<%= rawPath %>">download <%= basename %></a><%
         // requesting cross referenced file
         File xrefFile = null;
 
-        // Get the latest revision and redirect so that the revision number
+        // Get the latest revision and redirect so that  the revision number
         // appears in the URL.
-        String location = cfg.getLatestRevisionLocation();
+        String location = cfg.getRevisionLocation(cfg.getLatestRevision());
         if (location != null) {
             response.sendRedirect(location);
             return;
         } else {
+            if (!cfg.getEnv().isGenerateHtml()) {
+                // Economy mode is on and failed to get the last revision (presumably running with history turned off).
+                // Generate dummy revision string so that xref can be generated from the resource file directly.
+                location = cfg.getRevisionLocation(DUMMY_REVISION);
+                response.sendRedirect(location);
+                return;
+            }
+
             xrefFile = cfg.findDataFile();
         }
 
@@ -362,6 +375,10 @@ Click <a href="<%= rawPath %>">download <%= basename %></a><%
             Util.dumpXref(out, xrefFile, compressed, request.getContextPath());
     %></pre>
 </div><%
+        } else {
+            String error = "Failed to get xref file";
+%>
+<p class="error"><%= error %></p><%
         }
     }
 }