Bug 341842 microsummary service should be stricter about parsing generators, r=myk

browser/components/microsummaries/src/nsMicrosummaryService.js.in

@@ -1207,10 +1207,8 @@ MicrosummaryGenerator.prototype = {
     // in the microsummaries namespace, regardless of whether or not
     // it's the root element.  Should it matter?
     var generatorNode = xmlDocument.getElementsByTagNameNS(MICSUM_NS, "generator")[0];
-    // XXX We should throw instead of returning if the file doesn't contain
-    // a generator.
     if (!generatorNode)
-      return;
+      throw Components.results.NS_ERROR_FAILURE;
 
     this.name = generatorNode.getAttribute("name");
 
@@ -1223,11 +1221,21 @@ MicrosummaryGenerator.prototype = {
                  this.localURI; // locally created generator without sourceURI
     }
 
+    function getFirstChildByTagName(tagName, parentNode, namespace) {
+      var nodeList = parentNode.getElementsByTagNameNS(namespace, tagName);
+      for (var i = 0; i < nodeList.length; i++) {
+        // Make sure that the node is a direct descendent of the generator node
+        if (nodeList[i].parentNode == parentNode)
+          return nodeList[i];
+      }
+      return null;
+    }
+
     // Slurp the include/exclude rules that determine the pages to which
     // this generator applies.  Order is important, so we add the rules
     // in the order in which they appear in the XML.
     this._rules = [];
-    var pages = generatorNode.getElementsByTagNameNS(MICSUM_NS, "pages")[0];
+    var pages = getFirstChildByTagName("pages", generatorNode, MICSUM_NS);
     if (pages) {
       // XXX Make sure the pages tag exists.
       for ( var i = 0; i < pages.childNodes.length ; i++ ) {
@@ -1243,7 +1251,7 @@ MicrosummaryGenerator.prototype = {
 
     // allow the generators to set individual update values (even varying
     // depending on certain XPath expressions)
-    var update = generatorNode.getElementsByTagNameNS(MICSUM_NS, "update")[0] || null;
+    var update = getFirstChildByTagName("update", generatorNode, MICSUM_NS);
     if (update) {
       function _parseInterval(string) {
         // convert from minute fractions to milliseconds
@@ -1273,12 +1281,12 @@ MicrosummaryGenerator.prototype = {
       }
     }
 
-    var templateNode = generatorNode.getElementsByTagNameNS(MICSUM_NS, "template")[0];
+    var templateNode = getFirstChildByTagName("template", generatorNode, MICSUM_NS);
     if (templateNode) {
-      this.template = templateNode.getElementsByTagNameNS(XSLT_NS, "transform")[0]
-                      || templateNode.getElementsByTagNameNS(XSLT_NS, "stylesheet")[0];
+      this.template = getFirstChildByTagName("transform", templateNode, XSLT_NS) ||
+                      getFirstChildByTagName("stylesheet", templateNode, XSLT_NS);
     }
-      // XXX Make sure the template is a valid XSL transform sheet.
+    // XXX Make sure the template is a valid XSL transform sheet.
 
     this.loaded = true;
   },