chore(doc-gen): add processor to check for unbalanced code fences (backticks)

See https://github.com/angular/angular/pull/3213/files#diff-da1eabc74e0bafaa56d2bfe4bc223b05R19

Author: petebacondarwin

docs/docs-package/index.js

@@ -18,7 +18,7 @@ module.exports = new Package('angular-v2-docs', [jsdocPackage, nunjucksPackage,
 .processor(require('./processors/generateNavigationDoc'))
 .processor(require('./processors/extractTitleFromGuides'))
 .processor(require('./processors/createOverviewDump'))
-
+.processor(require('./processors/checkUnbalancedBackTicks'))
 
 // Configure the log service
 .config(function(log) {

docs/docs-package/processors/checkUnbalancedBackTicks.js

@@ -0,0 +1,28 @@
+var _ = require('lodash');
+
+/**
+ * @dgProcessor checkUnbalancedBackTicks
+ * @description
+ * Searches the rendered content for an odd number of (```) backticks,
+ * which would indicate an unbalanced pair and potentially a typo in the
+ * source content.
+ */
+module.exports = function checkUnbalancedBackTicks(log, createDocMessage) {
+
+  var BACKTICK_REGEX = /^ *```/gm;
+
+  return {
+    $runAfter: ['checkAnchorLinksProcessor'],
+    $process: function(docs) {
+      _.forEach(docs, function(doc) {
+        if ( doc.renderedContent ) {
+          var matches = doc.renderedContent.match(BACKTICK_REGEX);
+          if (matches && matches.length % 2 !== 0) {
+            log.warn(createDocMessage('checkUnbalancedBackTicks processor: unbalanced backticks found in rendered content', doc));
+            console.log(doc.renderedContent);
+          }
+        }
+      });
+    }
+  };
+};